The Quantum Thomist

Musings about quantum physics, classical philosophy, and the connection between the two.
Is Thomism really refuted by modern science?

Is Thomism really refuted by modern science? (Further Response)
Last modified on Sun Jun 6 11:33:19 2021

I am writing this in response to a reply to my previous post. I am posting the response as a post in its own right, because it has grown too long for a simple reply. First of all I will publish the comment, which is well worth reading, and then follow up with my response.

In my article, I said that Thomistic metaphysics was static and unchanging, whereas modern science demands a metaphysical view that keeps pace with our evolving scientific understanding of the reality of the world. Nothing in Bonnette's article gave me reason to think otherwise. As you alluded, his stance (as well as that of many Thomists') doesn't seem to be in complete agreement your own. But now I have to step back and re-assess what I said. Despite what I think I have heard from so many Thomists, perhaps there is room for change in Thomistic metaphysics.

But this brings up another issue. How much can Thomism be adapted to modern science before it can no longer be considered to be Thomism - the philosophy of Aquinas? Would he have agreed with you that a down-quark is the efficient cause of the W boson and the up-quark? It seems to me that this is something of a stretch. It still happens spontaneously, with no apparent triggering mechanism, which is what most of us would regard as an efficient cause.

And it seems to me that you are stretching more than just causality. In dismissing my criticism of essentialism, you side-step the main issue (dare I say the essential issue?). The point I raised is that there is not always clear distinction between the essence of one form and another. Your example is of a case where it is clearly defined, but my examples show that the distinction isn't always so sharp. I asked when an ape gives birth to a man. In evolution (didn't figure into Aquinas' calculus) there is no such distinction. Any dividing line you may wish to draw between one form and the other is arbitrary, and obviously subject to disagreement. But that casts doubt on one of the pillars of Thomistic philosophy.

And of course, there is still the matter of act and potency. You claim that this metaphysical concept is presupposed in all modern physics. Really? It's strange that I never heard any such thing (and I am not altogether uneducated in physics). It's not an underlying concept upon which other metaphysical concepts are based. There are no such dependencies, whether stated or otherwise. It's not something that can be quantified. It adds nothing to our understanding of any system of mechanics. And if you want to claim that it does, then you have to water it down so severely that it wouldn't be recognized by Aquinas.

If I'm not mistaken, his system of metaphysics was teleological. God was presumed, and things were purpose-driven, which is antithetical to any modern scientific metaphysical view. God was said to be pure act. Potency was the ability or tendency to move toward the the final end, which was seen as God's purpose for something in nature. This is what we understood as final causation. Now, you are telling us that these concepts are still presumed in modern science? I think you are mistaken. Or you have changed Thomistic philosophy by drastically that it wouldn't be recognized by Aquinas himself.

Thanks very much for your reply. I'll try to keep this brief, but almost certainly won't succeed.

I should note that am not a philosopher, nor a historian of philosophy, just somebody who has read the original sources and interpreted them as best I can. So I am writing this quickly based on a copy of Aristotle's works in front of me, an index; the text on a computer with a search function, and my vague memories of reading the text a little while ago. I don't claim to have an expert's breadth of knowledge at my fingertips, and thus it is possible that I haven't presented Aristotle completely fairly. If I have made a misrepresentation, I apologise. But I hope that I have done enough to show that my interpretation of Aristotle can at least be defended.

My intention has been to investigate whether an Aristotelian/Thomist interpretation of contemporary physics can be defended, and if so, promote a reformulation of Aristotelian philosophy that can be used as the basis of a philosophy of quantum physics. You will appreciate that this is not an easy task, if we want to do it properly. It is made harder because we are the cultural heirs of a 500 year old intellectual tradition which has generally misrepresented classical philosophy, and in particular changed a lot of the definitions. Contemporary Aristotelian philosophers claim that a lot of what is taught by other philosophers about Aristotle is mistaken. The only way to settle this is to lay aside any conceptions we have, and go back to the original sources.

This leaves us with a four step process.

  1. Find and read the original sources.
  2. Extract Aristotle's philosophy from his physics.
  3. Translate that philosophy into a more modern terminology.
  4. Consider how that philosophy might be applied in the circumstances relevant to today's physics, and whether it leads to a something consistent with modern physics.

The first step is easy. Translations of all the important works are just a quick google away.

The second step is harder. Firstly, Aristotle is not an easy read, particularly for those of us trained in a different intellectual tradition. Secondly, Aristotle's physics is certainly wrong. He brings in other assumptions beyond his metaphysics, such as his cosmology and the four element theory. Unfortunately, his philosophy is illustrated with examples taken from his physics, and those examples are at best irrelevant and at worst badly misguided. Reading Aristotle is often frustrating and annoying. The questions he addresses tend to be slightly different from the ones we would ask today. We have to piece things together from what he would say. And, of course, he would make some things much easier for himself if he expressed them mathematically. To see if there is anything we can salvage from his work, we need to extract the fundamental principles away from these images. Modern commentators help a lot here, but unfortunately still frequently fall back to Aristotelian examples. So I have a lot of sympathy for people who give up at this stage. However, it is possible to do this.

The third step is necessary, but dangerous. There is always the risk that I introduce some ideas of my own when doing the translation. But, if we compare Aristotelian philosophy against modern physics, we need to use a common language and notation. Since I am more committed to physics than I am to the philosophy, better to leave the physics as it is and re-express the philosophy. And it is easier to bring Aristotle up to date, than express physics in fourth century BC language.

Finally, the comparison. For me, this is the easiest step, though I know that many others have stumbled at this stage.

The reply contained four points. I will discuss each of these in turn, though not in the same order. My replies to several of these points are related to matters of terminology. So I will begin by quoting the classical sources, to see what Aquinas and Aristotle meant by the term. I will then re-express that meaning in my own words. And finally, show how it fits into modern physics. [I note that I took a few short cuts in my last section, so didn't apply this methodology there. Apologies for that.]

  1. Efficient causality. You ask whether St Thomas would have accepted my statement that the down quark is the efficient cause of the W- Boson. At one level, of course, St Thomas wasn't aware of up quarks and down quarks, and the mathematical framework used to describe the decay would have been alien to him. But I think that he would have had more sympathy with my description of efficient causality than you might realise. You state that most people today would regard some sort of triggering mechanism as the efficient cause. I would agree that most people think that. I used to be the same. But the question is not what people today think, but what Aristotle and Aquinas thought. Since Aquinas took Aristotle's views on causality, act, potency etc. as written (he developed other areas of Aristotle's thought, but not this), I will primary use Aristotle as my source here.

    Aristotle's definition of the efficient cause, as referenced in his physics (II.3), was

    Again (3) the primary source of the change or coming to rest; e.g. the man who gave advice is a cause, the father is cause of the child, and generally what makes of what is made and what causes change of what is changed.

    Now it is clear that each of the examples that Aristotle used for an efficient cause is a substance. We have a man, a father, a maker. Aristotle describes the cause as an object rather than a triggering mechanism. The term "efficient cause" isn't found in Aristotle as far as I can see; it's a name that was later applied to his concept. Instead he tends to use the terminology "mover" or "moving cause". For example, in Metaphysics XII.3

    For everything that changes is something and is changed by something and into something. That by which it is changed is the immediate mover; that which is changed, the matter; that into which it is changed, the form.

    Note, next, that each substance comes into being out of something that shares its name. (Natural objects and other things both rank as substances.) For things come into being either by art or by nature or by luck or by spontaneity. Now art is a principle of movement in something other than the thing moved, nature is a principle in the thing itself (for man begets man), and the other causes are privations of these two.

    The moving causes exist as things preceding the effects, but causes in the sense of definitions are simultaneous with their effects.

    In each of these quotes, Aristotle describes what can only be his efficient cause as a thing, i.e. some substance rather than a mechanism.

    While Aristotle claimed that everything except his first mover has an efficient cause, he did not object to spontaneous generation. Metaphysics VII.9

    The question might be raised, why some things are produced spontaneously as well as by art, e.g. health, while others are not, e.g. a house. The reason is that in some cases the matter which governs the production in the making and producing of any work of art, and in which a part of the product is present, some matter is such as to be set in motion by itself and some is not of this nature, and of the former kind some can move itself in the particular way required, while other matter is incapable of this; for many things can be set in motion by themselves but not in some particular way.

    While we rightly laugh at his examples, Aristotle had no objection to something coming into being without a triggering mechanism. I could also cite his belief that maggots might arise spontaneously in meat. His science was wrong, but it demonstrates that his philosophy is consistent with the idea that triggering mechanisms are not a necessary part of the chain of explanations. Yet he believed that everything had an efficient cause. Thus he could not have believed that efficient cause could be reduced to a triggering mechanism.

    Aristotle had no difficulties with things being the cause of their own motion (or change). Physics VIII.4

    Of things to which the motion is essential some derive their motion from themselves, others from something else: and in some cases their motion is natural, in others violent and unnatural.

    Finally (in my treatment of Aristotle), when he does discuss a "triggering mechanism", he makes it clear that it is distinct from both the mover (the efficient cause) and the moved. Physics VIII.1

    But at any rate all things that are capable respectively of affecting and being affected, or of causing motion and being moved, are capable of it not under all conditions, but only when they are in a particular condition and approach one another: so it is on the approach of one thing to another that the one causes motion and the other is moved, and when they are present under such conditions as rendered the one motive and the other movable.

    Thus the approach is needed to make the mover or efficient cause affective, but it is not in itself part of the description of the efficient cause, which is the mover by itself. I can't think of any place in Aristotle's work where he relates a triggering mechanism to an efficient cause. Instead, as far as I am aware always refers to an agent that institutes the process of change. Of course, I could be mistaken in saying that nowhere in Aristotle does he use a different understanding of efficient causality -- I am not an expert, and can't bring all of his work to mind -- but certainly this is the primary sense in which he describes efficient causes. He stated that in some cases circumstances need to align for the efficient cause to bring about its effect. But he also allowed for things to happen spontaneously without needing a particular set of circumstances. This is what we see in quantum physics. An electron may emit a photon and drop down an energy level (which is spontaneous), or absorb a photon and move up an energy level (which depends on circumstances). In my terminology, the efficient causes of the electron in the higher energy state are the photon and the electron in the lower energy state.

    I also note that Aquinas' second way, the cosmological argument based on efficient causality, depends on the version of causality that links one substance with another rather than via "triggering mechanisms".

    Thus my picture of the down quark decaying is an accurate implementation of Aristotle's idea of efficient causality. It contains the notions of causality linking substances, things containing the cause of their own motion within themselves, and the spontaneous generation of the W- Boson out of the down quark.

    The conservation of energy and momentum is respected in all quantum field theories. Every particle carries positive energy. Therefore (at least this side of a theory of quantum gravity), we can say that particles cannot come from nothing; a new particle can only emerge from the decay of another particle. Obviously, in some theories of quantum gravity, the negative energy of the gravitational field can cancel out the positive energy of the newly created mass. I don't believe that such theories are proved to be correct, but even if they were, the gravitational field would count as the efficient cause. However, a discussion of that goes beyond both the scope of this discussion and known physics.

    Thus, I think that my point that, while quantum physics destroys most formulations of causality, Aristotle's is consistent with it stands up well to scrutiny. The main stumbling block is that Aristotle meant a different thing by "efficient cause" than the definition used by most people since the Renaissance. So Aristotle's causality is often misrepresented and misunderstood.

  2. Teleology or final causality. Once again, there is a lot of misunderstanding over this concept. I personally blame the Renaissance (but again, I'm no historian of philosophy). At some point, the meaning of telos changed from end to purpose. I'll again begin with Aristotle's definition from Physics

    Again (4) in the sense of end or 'that for the sake of which' a thing is done, e.g. health is the cause of walking about. ('Why is he walking about?' we say. 'To be healthy', and, having said that, we think we have assigned the cause.)

    At first sight, this doesn't seem to help me much, with Aristotle's example from medicine not really applicable to physics. But when Aristotle turns to physical processes, it becomes clear that in this case he has something else in mind. Physics II.2, II.8

    Again, 'that for the sake of which', or the end, belongs to the same department of knowledge as the means. But the nature is the end or 'that for the sake of which'. For if a thing undergoes a continuous change and there is a stage which is last, this stage is the end or 'that for the sake of which'.

    Further, where a series has a completion, all the preceding steps are for the sake of that. Now surely as in intelligent action, so in nature; and as in nature, so it is in each action, if nothing interferes. Now intelligent action is for the sake of an end; therefore the nature of things also is so. Thus if a house, e.g. had been a thing made by nature, it would have been made in the same way as it is now by art; and if things made by nature were made also by art, they would come to be in the same way as by nature. Each step then in the series is for the sake of the next; and generally art partly completes what nature cannot bring to a finish, and partly imitates her. If, therefore, artificial products are for the sake of an end, so clearly also are natural products. The relation of the later to the earlier terms of the series is the same in both.

    So here, we are discussing a series of physical processes, similar to what we consider in particle physics. Now the "stage that is last" is a physical state, having the same standing as the stage that was first, meaning that final causality once again links one substance with another. So I took this idea in my adaptation of Aristotelian philosophy to quantum physics. The only thing I have added to this is the idea of indeterminacy (and I'm not sure that it is an addition to Thomistic thought): that a single object can have many possible ends. If the end marks the end effects of a possible physical process, then clearly the ends or final causes of a down quark include the up quark, electron and anti-neutrino.

    We can thus translate final causality to mean a list of the possible final states of a physical process acting on a given initial state.

    The opposition of teleology in physics basically states that physics can be described without reference to an (intellectual) purpose. [This doesn't mean that there is no intellectual purpose present, just that it is not part of the description provided by physics. I personally view the indeterminacy of quantum physics as a sign that physics isn't a complete description of reality; but that is a topic for another time.] But this just refers to the definition of final causality adopted during the Renaissance from (I think, but I could be mistaken) the writings of Cicero. It does not exclude the Aristotelian definition of final causality. Indeed, when particle physicists discuss "decay channels" today, they are just describing the possible end states of an unstable particle, precisely what Aristotle meant by final cause.

    The relevance of teleology in the Aristotelian sense is abundantly clear in quantum field theory. Take, for example, the Hamiltonian operator (which describes change in time) for a fermion in quantum electrodynamics.

    You need to have images turned on to see this.

    [Obviously we still need to renormalise everything; that doesn't affect my conclusions.] The creation and annihilation operators are usually used to describe the physical creation and annihilation of particles. But their role when we perform computations in QFT is slightly different. The annihilation operator basically scans for initial states. This term in the Hamiltonian seeks out a fermion at location x. The creation operators describes final states. So what this equation states is that if we start out with a fermion, then the possible final states are either a fermion in the same state (the mass term), or a fermion that has either emitted or absorbed a photon (the photon term), or a fermion in a neighbouring location (the derivative term). In other words, the central object in QFT describes the possible end states of a given initial state. And this is Aristotelian teleology, at the centre of our modern description of physics.

    When you say that "God was presumed" in Aquinas' teleology, I think you have things the wrong way round. Aquinas took his teleology from Aristotle pretty much unchanged, who maintained that motion and ends were wholly natural. The only place where God entered Aristotle's thought was as the terminus of the cosmological argument (the series of movers). So the presumption in Aquinas' thought was that things had natural ends, in the sense that I have described above. The fifth way was an attempt to demonstrate the existence of God from the premise that final causes exist in nature. You might not think much of Aquinas, but he clearly wasn't so much of an idiot that he would take as his premise something that presumed his conclusion. The existence of God was not an assumption of Aquinas' teleology, but a conclusion which Aquinas (but not Aristotle, who shared the same teleology) drew from it.

    I am not claiming that (intellectual) purpose in the universe has a place in modern science (although I believe that it can be inferred from the best scientific theory, but that is a philosophical argument building on a scientific theory which began by assuming no purpose). But I am claiming that the idea that an initial state can lead to certain final states but not others, Aristotle's understanding of teleology, is implicit in all forms of modern science from Newton to the present day.

  3. Act and Potency. I claim that this concept is presupposed in all modern physics. I would fully agree with you that the words "Act" and "Potency" won't be found in any physics textbook since the middle ages. But my claim is that the concepts are still there, just called by a different name (or sometimes presumed without being stated).

    I am going primarily to have to describe in my own language the concept as I understand it, since I can't find a single brief quote in the source work that expresses concisely what I want to say. I think my interpretation of this can be exegeted out of the sources, but were I to quote explicit passages as I did in the previous examples, there would be too much to filter out. Aristotle gave five possible definitions of potency in his metaphysics. The main one refers to a principle that allows for change. Both the actual and the potential refer to physical objects. Aristotle uses the example of a statue that could be carved out of a block of marble. Currently it is a block of marble actually, while the statue exists potentially. Thus a potency points to something which could be an actual object.

    The thing with the greatest degree of potency is pure matter, because this could be turned into everything. Thus all the possible substances which could be formed out of that matter exist potentially within that matter.

    Another important sense in which Aristotle uses potentiality is to describe the parts of a being. So, if one has a composite being, then one can't say that the parts themselves exist actually (since they are combined within a being). But instead they do exist potentially. I would use the example of a string (one of Aristotle's examples applied to a physical object). One could in principle cut the string in the middle and turn it into two short strings. Those short strings don't exist actually until the string is cut, but they are nonetheless in some sense contained within it. Aristotle states that they exist potentially, in the sense that the longer string has the capacity of being turned into two short strings.

    We can also apply the concept of potency to the ability to rearrange matter to give it a different shape. Aquinas discusses this in his commentary on Aristotle's metaphysics, part 5.

    And there are some things to which both of these apply, because in a sense the position of their parts accounts for their differences; and of these we use both terms—all and whole. And these are the things in which, when the parts are interchanged, the matter remains the same but not the form or shape. This is clear, for example, in the case of wax; for no matter how its parts are interchanged the wax still remains, but it does not have the same shape. The same is true of a garment and of all things which have like parts and take on a different shape. For even though liquids have like parts, they cannot have a shape of their own, because they are not limited by their own boundaries but by those of other things. Hence when their parts are interchanged no change occurs in anything that is proper to them. The reason for this difference is that the term all is distributive and therefore requires an actual multitude or one in proximate potency to act; and because those things have like parts, they are divided into parts entirely similar to the whole, and in that manner multiplication of the whole takes place. For if every part of water is water, then in each part of water there are many waters, although they are present potentially.

    We can go a bit beyond Aquinas' picture here, and consider the difference between some still water and water containing waves. In some sense, they are the same substance. The difference is merely a rearrangement of the parts. The difference is that at any one moment, one of these possibilities is actual, and the others remain potential. Thus potency also applies when we rearrange or move matter, such as in the example of the wax candle.

    In his commentary on metaphysics, book 7, Aquinas wrote,

    For in these sensible bodies, which all men admit to be substances, there are certain attributes such as the affections of bodies, for example, hot and cold and the like, which are evidently not substances. And in these bodies there are also “certain activities,” i.e., processes of generation and corruption and motions, which are clearly not substances. And in them there are also potencies, which are the principles of these activities and motions, i.e., potencies of acting and being acted upon, which are present in things; and it is also clear that these are not substances, but that they rather belong to the genus of quality.

    Here Aquinas states that there are attributes within substances. For example, something might be either hot or cold. But equally there is the action of moving from cold to hot. This change is obviously, to Aristotle and Aquinas, described in terms of act and potency. The being is actually in a state where it is cold, and potentially in a state where it could be hot. But Aquinas also states that because the motion can happen, then within the actually cold substance, there must be potencies. Since a potency always refers to a thing, this means that the same being heated resides or exists potentially within the cold being.

    There is one further application of potency which I need to discuss, and that is the presence of potency in a universal (which in this context I mean the description of beings of the same type -- the concept of universals is often applied to properties, but that's not what I am describing here). The discussion I want to focus on here is in Aristotle's first book of his physics, where he discusses act and potency as a rival to the other theories of motion and change. Aquinas' commentary on this states,

    That universals are confused is clear. For universals contain in themselves their species in potency. And whoever knows something in the universal knows it indistinctly. The knowledge, however, becomes distinct when each of the things which are contained in potency in the universal is known in act. For he who knows animal does not know the rational except in potency. Thus knowing something in potency is prior to knowing it in act. Therefore, according to this order of learning, in which we proceed from potency to act, we know animal before we know man.

    It would seem, however, that this is contrary to what the Philosopher says in Posterior Analytics, I:2, namely, that singulars are better known to us, whereas the universals are better known by nature or simply. But it must be understood that there he takes as singulars the individual sensible things themselves, which are better known to us because the knowledge of sense, which is of singulars, does precede in us the knowledge of the intellect, which is of universals. And because intellectual knowledge is more perfect, and because the universals are intelligible in act, whereas the singulars are not (since they are material), the universals are better known simply and according to nature.

    Here Aquinas is distinguishing between a universal, the species described by that universal, and singulars (that is individual members of the species). When he says that universals are confused, he means that that they don't describe one singular member of the species, but the species as a whole, with all the differences and distinctions that entails. So, for example, we may take the universal that describes the hydrogen atom. The singular would be one particular hydrogen atom in one particular state. All hydrogen atoms would be part of the species. The universal is (in part) a description of the set of every possible state of a hydrogen atom. When Aquinas discusses that the universals contain in themselves their species in potency, he seems to me to be saying that once we have awareness of the universal, from that concept we understand the set of states that could potentially exist. The potentia are thus the set of possible states of that being. We observe one of these states when that particular potency is actualised. But just as the singular state still reflects the universal, the other possible states of the being are contained within it as potency.

    So the potencies of a being can be defined as the set of possible actual states of that being. If this being exists in reality, then one of those states will be observed as actual, and the others in potency. If it doesn't exist in reality, then all the states exist as potencies. And this I will take as the primary definition of act, potency and potentia.

    Now you will rightly ask what any of this has got to do with modern physics. And at first sight, the answer is indeed not very much. But let us look deeper. Since the topic is quantum physics, I'll use an example from quantum physics, the hydrogen atom.

    We know that in Schroedinger quantum mechanics (the same fundamental principle carries forward into field theory, but since I understand this example better in the QM description, I will use that), the electron in the hydrogen atom is described by Schroedinger's equation with a Coulomb potential energy. This is a differential equation acting on the wavefunction or probability amplitude of the electron, which in turn describes the likelihood that we will find the electron at any given place. Now, the Schroedinger equation strongly restricts the possible solutions which the wavefunction could have. These are distinguished by three integers, the positive n which indicates the energy level, and two which describe the angular momentum of the electron. The energy of each of these solutions is (baring some corrections from magnetic and other interactions which I am neglecting here) proportional to 1/n^2.

    It is customary to discuss these solutions as different states of the system. They are, as discussed, discrete, characterised by various different integers. One cannot get from one to the other via a continuous change. At any one moment, when we take a measurement, we will find the system in one of these states. But it could, and does, transit to one of the other states.

    The mathematical description of the atom describes all these states. That alone cannot say which one we will find the electron in when we take a measurement. In terms of the actual physical object which we observe only one of these states exists at a given time (I discussed superposition briefly in my original post). But equally the other states still play a role, since the electron can only transit to them. We can't say that those other states don't exist, since they are part of the mathematical description. Equally, we can't say that they do exist in the same sense that we say that the state which is currently occupied exists, because they are not tangible. We thus need a third option to describe hydrogen atoms existing in states which could be occupied but which happen not to be occupied.

    And this is where the connection with Aristotle comes in. He uses very different language, but what he describes in the concept of potential existence is precisely that middle ground between tangible existence and non-existence which we need to describe the full set of states of the Hydrogen atom. The state of the atom that is currently occupied is actual; the other states exist in potency. In Aristotle, the potencies describe the possible substances that could arise after a change. In quantum mechanics, the non-occupied other states of the atom describe the states which the atom could change into. In Aristotle, actuality describes the being as it is in tangible existence. In quantum mechanics, we speak of one of the particle being measured to be in one particular state, or that that state is occupied.

    I perhaps go a little bit beyond Aristotle and Aquinas in defining the potentia of a system as any way in which it could possibly exist. In quantum mechanics, this would refer to the eigenfunctions of the Schroedinger equation; in field theory it refers to the Fock states associated with the renormalised creation and annihilation operators. In this, I follow the terminology of Heisenberg in his Philosophy and Physics. One of these states is in act (again, the concept of superposition complicates matters, but I discussed that in my previous post), with all the properties that Aristotle attributes to act. The others states are in potency, with all the attributes that Aristotle assigned to potency.

    So when I say that the theory of act and potency underlies quantum physics, this is what I mean. Quantum physics presupposes a set of Hilbert states, the eigenstates of the Hamiltonian operator. [I had better define what I mean by that. One form of the Schroedinger equation states that the Hamiltonian operator acting on the wavefunction is equal to the energy times the wavefunction. It is basically a mathematical operator that takes in one function and spews out what is usually a different function. Only in a few limited examples do you get the output as something proportional to the input. The eigenstates are the possible solutions to this equation. The Schroedinger equation doesn't continue in this form into quantum field theory, but the concepts of the Hamiltonian operator and eigenstates do, which is why I express things in this more general language.] You might quibble about whether this is a presupposition or a conclusion of quantum mechanics, but the mathematical structure that field theory depends on certainly presupposes it. But these states have precisely the same role in quantum physics as the actual and potential beings do in Aristotle's philosophy. Thus we can identify the eigenstates with the Aristotelian potentia. Since that physics can be described in terms of such states is presupposed by quantum physics, we can say that the theory of act and potency is presupposed by quantum physics. The words are not used by quantum physicists because a different language has been adopted. But the same concept is there. Once you have these states, then you can start calculating things such as the likelihood that a particle will transition to one state to another, or decay, or whatever.

    In my book, I also express classical mechanics in the same language of states. My motivation there is as part of an introduction to quantum physics, and I don't discuss the philosophical implications. But that classical mechanics can be expressed in such a language means that that formulation of it at least also depends on the concepts of act and potency.

  4. Essentialism. I gave the example of an ethanol molecule to argue that essence is a real thing. One ethanol molecule is the same as any other, which is what we mean when we talk about essences. You gave the example of the sand dune and the transitional form between a monkey and a man to say that essentialism isn't a real concept.

    Now I could retort that the topic of this discussion is quantum physics, and the ethanol molecule is considerably closer to an object of study of quantum physics than a sand dune, and thus the more pertinent example. But I don't think that will satisfy you, so I ought to elaborate.

    There are two different ways in which we can consider the essence of some substance. We can group things together by identity, or by similarity. The two senses of essence are merely analogous to each other.

    In fundamental physics and chemistry, the essences are described by identity. One electron is indistinguishable from any other electron. They all have the same mass, coupling to the photon, the same energy levels and so on. The Pauli exclusion principle (which only applies to identical particles) makes it clear that this is not an accidental similarity, but a definite part of nature. The same applies to composite particles such as protons, and going further afield to the atoms and molecules that are studied by chemistry. The example I gave was of this class. One ethanol molecule is the same as any other ethanol molecule (baring that in one of them one state might be actual, and in the other some different state might be actual, but the two molecules have the same potentia, and the essence describes the set of all potentia, not which one happens to be actual at any given moment).

    Biological species are at the other extreme. Here we group animals together not by identity, but on the basis of similarity. One monkey is not identical to another monkey of the same species, but only similar in certain respects. Because they are marked by similarity rather than identity, there is ambiguity about where we draw the lines between different species. However, this doesn't deny essentialism in physics. Each monkey is made of various molecules and polymers, and these are identical to any other molecule and polymer of the same type. Thus physical essentialism still applies at a more fundamental level even when we discuss biological species. Thus ambiguity in finding essences at the biological level doesn't really influence the discussion at the level of physics and chemistry. When we talk about the essence of a biological species and the essence of a protein, we are discussing different things.

    So the question is whether it is useful to discuss essences at a biological level. Generally, it is easy to draw boundaries between objects where the difference between one and the other is discontinuous. That's how we can distinguish ethanol from methanol: there isn't an intermediate state between them. Clearly, at one level we can do this in biology. Not every species is connected by small changes. For example, insects have 6 limbs, mammals four. That's a discontinuous change, and it is easy to draw a line between them. Different species have different numbers of chromosomes. Obviously, evolution can still explain how a mutation can allow something with twenty chromosomes to give birth to something with 21, but the mutation which does this still leads to a clear discontinuity in the structure of the animal. So not every biological change is continuous. At a crude level, those discontinuities allow us to draw lines around groups of organisms even though they evolved from each other.

    Aristotle defined humanity as a rational animal. Rationality in this case means (or contains the meaning) of being able to form abstract representations of objects, either in thought, language, mathematics, art and so on. This is a discontinuous change in the evolution of species. Either you can do this, or you can't. Admittedly some people are better at doing it than others, but even if you can't do it well, you still can do it. The claim (I'm not up to date with biological research in this area, so can't comment on how accurate this claim is) is that this is something that we as a species can do, but other animals including our evolutionary ancestors can't. [I recognise that some birds and primates are able to use tools for some tasks, but one can do that without abstract thinking in the sense that I mean.] There was thus along the evolutionary chain, at least one point where a mutation led to a non-rational animal giving birth to a rational animal. This is a discontinuous change, and can be used to distinguish between the species [species here is used in the Aristotelian rather than modern definition].

    At some point, we had a common ancestor, and the evolutionary chain split, with one branch leading to modern chimpanzees, another to gorillas, and the other to modern humans, and so on. Mankind is certainly rational. If chimpanzees, gorillas, etc. aren't capable of abstract representation, then the break occurred some point or points along the chain from that common ancestor to ourselves. The hominid on one side of the change was a non-rational animal, the hominid on the other side was a rational animal and thus (by the Aristotelian definition) human. If it turns out that other primates are capable of abstract thought, then the break occurred somewhere on the path between the monkeys and the primates.

    I expect you will object that I using Aristotelian definitions of species instead of more modern biological ones, dividing things in terms of animal and rational animal rather than distinguishing between snow leopards and African leopards, for example. But what I am trying to do is to show that discussing essences in this fashion is consistent with evolution. I don't want to make any further claims here than consistency; I leave it to Thomists who specialise in biology to draw things further than that, if they can.

    Another possibility is to define ideal archetypes which are that individual or those groups of individuals which are best suited to their environment (in the sense required by natural selection), and define a species [in the modern sense of the word] as those which are capable of interbreeding with those ideals to produce fertile offspring. This leaves the question of what to do with those individual animals capable of interbreeding with two disjointed archetypes (I would then class all of those beings into one species). Then we have those possible individual animals which aren't capable of interbreeding with any archetype. These I would class into a separate species of transitional forms. I am not a biologist, so I don't know whether this idea would work in practice. But if it plausible, then it remains a possible way to distinguish essences of species.

    But I would be better turning this question to those Thomists who have more of an interest in biology than I do. I am, however, convinced that the problems with essentialism in biology don't create difficulties for essentialism in physics, which is my main concern. The word "Essence" means slightly different things in biology and physics.

    With regards to sand dunes, the issue is a different one. We first of all have to consider the grain of sand itself. This I take to be a small speck of a mineral crystal, and thus it falls under the purview of the physical essentialism. Of course, different grains of sand might have different mineral compositions and thus belong to different essences, but that doesn't change the overall picture.

    Then we come to sand as a whole. The essence of sand is that it is a collection of grains of sand (we have the ambiguity here, of course, of what counts as a sand grain; how big it has to be -- I'll leave this to one side). Once again, essence is used analogously with how we describe the essence of an ethanol molecule. So difficulties in defining essences here don't necessarily mean that there are difficulties at the level of physics. The constituents of an ethanol molecule are tightly bound together into a single substance. The constituents of sand are only very minimally bound, if at all. In terms of the metaphysics of the thing, that's a big difference.

    But let's ignore those caveats, and proceed. Sand is the substance. That sand can exist in numerous different shapes and structures. So sand might be actually flat and potentially a sand dune, or actually a sand dune and potentially flat. So when you refer to sand dunes, you are drawing a line, not around a substance as a whole, but around a set of potentia within that substance, and arbitrarily separating them off from other potentia. Difficulties in defining what is and what isn't a sand dune arise because you have artificially drawn a line through a substance. Essence applies to substances, not potentia within a substance. Thus, in Aristotelian thought, a sand grain has an essence. Sand, if the caveats I raised before can be overcome, has an essence. But a sand dune doesn't, because it refers to only some of the potentia of a form. This in no way destroys essentialism (not least because the fundamental constituents of sand have essences, so it is not as though we have described a system without any reference to essence): it just means that we have to be careful what we apply it to.

    Thus, while I can see how your example might be a problem for those other forms of essentialism which don't allow for an essence to have different potentia, I don't see how it is a difficulty for a strictly Aristotelian essentialism. And particularly not when we are discussing essentialism in theoretical physics.

Why Is There Something, Rather Than Nothing? (Part 3)

Reader Comments:

1. Scott Lynch
Posted at 21:16:41 Sunday December 2 2018

Great Post Again!

Dr. Cundy,

I know that Aristotle typically divided biological species into vegetative, sensitive, and rational. I do not know to what extent he got more specific than this. It seems that a Thomist or Aristotelian could claim that there are only three species of life forms or three biological essences. In fact, you could even get rid of vegetative essences and still keep essentialism. I don’t think that would be wise, but it is possible. Typically people distinguish substances (or essences) by their powers (especially if they do not supervenes on more fundamental ones). That is why sensation is a marker for a new type of living being. You have this discontinuous jump from no qualia to qualia. Again this is all just ontological interpretations of the metaphysics, not really debate about the metaphysics itself.

I 100% agree that it is frustrating reading the outdated physical examples provided by Aquinas and Aristotle. The one benefit though is they still elucidate the metaphysics just as well as long as the physical systems are logically possible. For example, it is theoretically possible (not logically contradictory) to have a four element universe. In that case, the general metaphysical principles underlying that universe will apply just as much to our universe. It just turns out that the individual facts (and thus our interpretations of the facts) are different.

As far as biological essentialism is concerned. Have you read anything that attempts to give an in depth break-down of differentiating living organisms from composites of organic compounds utilizing modern biochemistry and Aristotelian-Thomistic principles?

1. im-skeptical
Posted at 16:17:02 Monday December 3 2018

Regarding the efficient cause: I agree that what I said earlier was not strictly correct in the sense that Aristotle meant. The efficient cause is more properly regarded as the agent that causes movement. I should amend my statement from "some kind of triggering mechanism" to "some kind of mover that is not the thing itself". Now it does appear that while Aristotle allows for certain spontaneous actions, it also appears that Aquinas does not. I note that his argument from motion specifically says that things that are moved are moved by something else. And indeed, this is his basis for asserting a first mover. In fact, if he allowed for something to move itself, the argument from motion doesn't stand. So with that in mind, (and considering that the topic of discussion is Thomism as it relates to modern science), I must ask once again, what would Aquinas have to say about your theory that the particle that spontaneously decays is the mover that is itself not moved by another thing? And would he then be able to conclude that there must be a first mover?

Regarding teleology and final cause: You say that "Aquinas took his teleology from Aristotle pretty much unchanged". But I think this is one case where there is a distinct difference. Because while Aristotle discusses intelligent actions and natural actions as different in kind, Aquinas specifically says all final ends are intelligently conceived. That is the basis of his fifth way - the teleological argument. You say "The existence of God was not an assumption of Aquinas' teleology, but a conclusion which Aquinas ... drew from it." But I say that without his presumption of intelligent design in nature, he wouldn't be able to draw that conclusion. Furthermore, modern science is certainly not built on any such notion. Evolution specifically rejects it.

Regarding act and potency: You say "Both the actual and the potential refer to physical objects." I can't quite see it that way. It would make more sense to regard act and potency as properties of things, and when viewed in conjunction, they provide the impetus for change. But the way the terms "actual" and "potential" are used by Thomists seems to be inappropriate as a description of that concept. If act and potency are a properties of things that provide impetus for change, then it serves little purpose to describe a state of affairs as being "actually one thing and potentially something else". Yes, we can all agree that a statement like that could apply to virtually anything at all (including the states of objects modern physics), but it does not convey the meaning of the concept that act and potency provide the impetus for change. Also, act and potency do not provide any meaningful description of the means by which things change. As a metaphysical concept they are essentially useless in physics. They are not measurable properties. They can't be used in any calculation to determine what the future state will be. Even in Schroedinger's wave equation, where we can't precisely predict a future state, we at least have a useful probability distribution which is calculated without any reference to act and potency. But especially outside the realm of quantum mechanics, we do have precise physical descriptions of the mechanisms of change (involving the metaphysical concepts of force, mass, and energy), act and potency are nothing more than vague, hand-waving concepts by comparison that play no role at all in physics. And when connected with Aquinas' ideas of divine causality, they are antithetical to modern science.

Regarding essentialism: It is interesting that you want to define essence only in discrete differences between species. This leads to serious problems in your theory, as well as an unscientific outlook. For example, you claim that due to a DNA mutation, a non-rational animal gave birth at some point to a rational animal, and that was the genesis of mankind. And then you tell us that this is consistent with evolution. The problem is that no anthropologist or evolutionary scientist thinks that's what happened. Rationality is not a binary thing. What we observe among animals with brains is whole range of cognitive abilities. Various animals exhibit what you might consider to be a surprising level of logical thinking and even abstract thinking. This is not unique to mankind. And it is not something that suddenly appeared. It evolved gradually, like most anatomical features do. The point I made about an ape giving birth to a man is that such an event never happened. Rather, there was a gradual transition. From an evolutionary perspective, the idea of distinct species is not realistic. And that has implications for your essentialism. What is the essence of the half-way-between creature? What about its immediate ancestor or offspring? One way to solve your problem is to say that each generation defines a unique species with its own form and essence. And you could take that idea one step further to say that each unique individual has its own unique essence. But, as I hope you can see, that Thomistic essentialism simply doesn't comport with scientific reality.

2. Nigel Cundy
Posted at 21:10:26 Monday December 3 2018

Response to Scott Lynch

Thanks once again for your kind words.

I am not aware of any works on biochemistry from an Aristotelian-Thomist perspective, however that doesn't mean there aren't any. It is not something I have as yet had a chance to look into. I agree, though, it is something that is needed.

3. Nigel Cundy
Posted at 23:51:37 Monday December 3 2018

Response to Im-skeptical

Thanks once again for your reply. I'll be briefer this time [A little].

1) Your question concerning the first way is an interesting one. I think that Aquinas' argument can be extended without too many problems to allow for a thing in one state to be the mover that preceded that same thing in another state. I discuss this a bit in my book.

Aquinas himself, I think, took a different route to resolve this problem. The first way is a summary of Aristotle's argument from Physics VII and Physics VIII. In Physics VIII.4, Aristotle discusses this very question (obviously in the context of his own physics). In Aquinas' commentary on the Physics, he concludes his discussion of Physics VIII.4 by saying (referring back to the preceding text, which I haven't quoted since it is a bit longer),

while others, such as heavy and light things are moved according to nature not by themselves but by some mover) as has been explained -- for they are moved either per se by the generator which makes them be heavy and light, or they are moved per accidens by whatever removes what impedes or removes their natural motion -- it is accordingly clear that all things which are moved are moved by something, i.e., either by an intrinsic or an extrinsic mover; which is to be moved by something other.

I'll focus on the per accidens solution. If you have a heavy object high up, it naturally falls, apparently moving itself according to its natural tendencies (you'll have to excuse the out of date physics -- we are trying to extract the principle behind it). The thing that moved it, in Aquinas' terms, would then be whatever lifted it up and held it there in the first place. This solution can be transferred to at least some quantum physics problems. If an electron in an excited state around the atom spontaneously decays into a ground state, then its mover would be whatever excited it in the first place. I think this argument would also work in QFT, although its a bit harder. Something can only decay or emit a particle if it has sufficient energy (in all inertial frames). Since the thing has a minimum energy (its mass in classical physics and relativistic quantum mechanics, zero in QFT); either it stayed in an unnaturally high energy state forever (which other aspects of the cosmological argument would address), or something excited it into that state. So that thing which elevated it into the excited state would be its mover. That, at least, based on his comments in his commentary, is how I would imagine Aquinas would answer the question. [I think that the solution I mentioned works a bit better in the context of QFT, which is why I prefer it.]

So I diverge from Aquinas a bit here. But whether you take my solution or his, it would still work in the first way.

2) Teleology. Firstly, I dispute the phrasing "intelligent design" here, because of the way that it is used by modern creationists. They have a very different (mechanistic) natural philosophy to Aquinas, and since it is wrong to compare modern arguments from design with Aquinas' fifth way (once again I discuss this in my book; I spend one chapter showing how modern criticisms of the first and fifth way miss the point, before developing my own, slightly different, arguments), I tend to have a reaction against language that might mislead people into thinking they are the same thing.

In my post, I gave a couple of quotes from Aristotle suggesting that my interpretation of telos is in agreement with at least one sense of what he meant by the term. The question is then whether Aquinas would have accepted Aristotle's definition more or less as it stood (and thus God enters as a consequence of his teleology) -- as I claim, or added a notion of God's purpose to it (so that the God becomes a premise of his Teleology) -- as you claim. I think the only way to settle this is to look at what he wrote elsewhere. Aristotle introduced the causes in Physics II, and as part of his discussion of that section of Aristotle, Aquinas wrote,

The second point is that some things are causes of each other in respect to different species of cause. Thus work is an efficient cause of a good habit, yet a good habit is a final cause of work. For nothing prevents a thing from being prior and posterior to another according to different aspects. The end is prior according to reason, but posterior in existence; the converse is true of the agent.

So in this passage, he firstly treats the end (or final cause) as the opposite of the efficient cause (albeit, and unfortunately, not in an example taken from physics). Two sentences later, he states that the end comes after the being in order of existence. It can hardly refer to God or his purposes in that case. I didn't find anything in Aquinas' commentaries which he didn't follow Aristotle pretty closely in this matter. But I'm not an expert, so I could be mistaken. Do you have any counterexamples (excluding the fifth way, whose interpretation we are disputing) to suggest that Aquinas did intend final cause to mean purpose?

3) With regards to act and potency, we seem to be in agreement that my interpretation of the concept of act and potency is consistent with modern physics. The question is whether it is consistent with how Aristotle and Aquinas defined it. [And, actually, I would agree that I have developed their position a little -- but I would say it is a legitimate development, while you seem to regard it as a distortion.] Admittedly, this is a tricky task, because in my reading neither Aristotle nor Aquinas are as clear as I would like when discussing this subject. But I referred to an illustration from Aristotle and a couple of citations from Aquinas supporting my idea that their understanding of potency is something that points to what we would now call different states of being. Do you dispute my interpretation of those passages, or have any passages which can back up your claim that they interpreted it as "properties of things which provide an impetus for change?" (To my mind, the natural powers or tendencies of things towards certain ends provides the impetus for change in their physics and philosophy.)

Now it is certainly true that my interpretation of act and potency doesn't explain the mechanism for change. But it is not intended to. As I said, I regard the notion of potency (properly translated into mathematical notion) as a necessary axiom of any physical theory. Act and potency describes what changes are possible. The theory you build on top of that (whether expressed in terms of natural powers, or forces and energy, or the creation and annihilation of particles) is what describes the mechanism. I discussed how the concepts of force, mass and energy aren't relevant to this point (or, in the case of force, to contemporary physics) in my first post.

4) Now, as is obvious, I'm not a biologist, and I am usually reluctant to get into arguments over biology. I've seen how badly non-physicists fare in discussions of physics, (or indeed non-classical philosophers when it comes to classical philosophy), and I have always felt that there is no reason to suppose that I would be any better if I ventured into a discussion on biology or some other subject in which I am not expert. So I try to avoid it as much as I can. It looks like I should have heeded my own advice. I'll leave it to a biologist or anthropologist to answer you here. [And, actually, I personally depart from Aquinas in another way here; I do regard each individual to have their own essence, in part to avoid the issues you have discussed. I regard this issue in the same way as I regard the unification between QFT and GR -- I haven't yet seen a good answer, but I trust that there is one (in part because non-essentialist theories have even bigger problems), though it will take a brainer man than me to find it.]

But there was another point I made. Why is biology even relevant to this discussion? The contact between metaphysics and science occurs first and foremost in fundamental or quantum physics. Biological processes (I am assuming) ultimately reduce to chemical and physical processes. Chemical processes reduce to physical processes. So if a Thomist can explain physics in terms of his metaphysical principles, then he gets chemistry and biology thrown in as well. Even if the essences are only at the level of chemicals, or perhaps individual animals, rather than species, that still means that essences have a fundamental role in the philosophy of science. I have argued that it makes sense to describe the essence of fundamental particles (related to the various states generated by the different types of creation operators in renormalised and effective field theories), and that the exclusion principle shows that these essences are not merely a human construction but inherent within nature. Do you have any arguments to dispute the case for essentialism in fundamental physics?

4. im-skeptical
Posted at 18:48:04 Tuesday December 4 2018

If an electron in an excited state around the atom spontaneously decays into a ground state, then its mover would be whatever excited it in the first place.

- Well, OK. That's one way of looking at it. Things have a "natural tendency" to fall after they are lifted (by the efficient cause). In the case of the electron, there's no telling how long it will take, but I suppose that's within the framework of Aristotelian metaphysics. I will note, however, that this answer seems to disagree with the one you gave earlier (the particle is the efficient cause of its decay products).

Do you have any counterexamples (excluding the fifth way, whose interpretation we are disputing) to suggest that Aquinas did intend final cause to mean purpose?

- I think final cause is generally understood as the intent of the agent that acts. This is necessarily conceived by a mind of some kind, since simple objects like rocks do not have any intent. And Aquinas does tell us that natural things (as opposed to things that are moved by men) act in accordance with God's purpose. Aquinas uses the phrase "the intention of an end" when discussing final cause:

Matter does not acquire form, except according as it is moved by an acting cause (agent); for nothing reduces itself from potency to act. But the acting cause does not move, except by reason of the intention of an end. For if the acting cause were not determined to some effect, it would not act to produce one rather than another. In order, therefore, that it should produce a determined effect, it is necessary that it should be determined to something certain as end. (Summa theol. I-II:1:2).

With regards to act and potency, we seem to be in agreement that my interpretation of the concept of act and potency is consistent with modern physics.

- The point I made is that the concept of act and potency, though it may be construed as being consistent, is useless in modern physics. It offers nothing more than a vague notion of the behavior things, that can be applied to anything and everything. It plays no role in calculating or predicting motion.

Do you have any arguments to dispute the case for essentialism in fundamental physics?

- My argument is of a more general nature. If we can show that doesn't apply to biological species (and I think I have done that), or in innumerable other circumstances where things do not fall into discrete categories, then why should we think that it is a valid metaphysical concept under any circumstances?

5. Scott Lynch
Posted at 05:17:41 Thursday December 6 2018

Response to im-skeptical


“I think final cause is generally understood as the intent of the agent that acts..”

Aquinas would agree that God providentially orders all things with intent, but that is a consequence of his 5th Way, not an assumption. The assumption is that all things act for a certain end or limited range of ends. This does not mean “purpose”. The rock has no “purpose” for falling to the floor. What Aquinas is getting at is that, logically, there is no reason the rock should not move away from the earth, or parallel to the earth, or not at all. That it always (or almost always) does fall to the earth is either by sheer luck, or it is by nature (its telos). Now for it to be dumb luck would not explain why the rock always falls to the earth (for surely if it was possible to be repelled by the earth, it would do so eventually, just as if you flip a fair coin 1000 times, you will eventually get tails. So it must be because of its telos or final cause. But for any finite or contingent thing to have a final cause will ultimately require an intelligent agent specifying that final cause (selecting it so to speak out of an infinite range of possible natures). This intelligent final cause could either be immediate or the terminus of a potentially infinite hierarchical series of final causes, but either way, you need the intelligent cause to get the final cause. So that is how Aquinas gets his intelligent God. You’ll notice he does not even presume teleology, he argues for it on the basis of the consistency and order of the world. Then he goes from there to argue for an intelligent agent, God.

“The point I made is that the concept of act and potency, though it may be construed as being consistent, is useless in modern physics. It offers nothing more than a vague notion of the behavior things, that can be applied to anything and everything. It plays no role in calculating or predicting motion.”

I feel like you are once again confusing physics with metaphysics. Metaphysics is not supposed to have predictive value except for in a very general sense (things will change, have causes, explanations, etc.). The point of metaphysics is to provide an ontological framework that is consistent with any type of physics. If we found a unifying theory of QFT and GR tomorrow, Thomistic metaphysics would be just as applicable. If we woke up and found out we were living in a matrix our whole lives and physics is really the way the Ancient Greeks thought it was with their four-element theory, Thomistic metaphysics would still be as applicable. To be sure, the ontological interpretations we assign to various phenomena would change, but the underlying principles (act, potency, causality, etc.) would remain the same.

“My argument is of a more general nature. If we can show that doesn't apply to biological species (and I think I have done that), or in innumerable other circumstances where things do not fall into discrete categories, then why should we think that it is a valid metaphysical concept under any circumstances?”

Dr. Cundy has shown you why. He has given a few examples based on the different essences that certain atoms or molecules have (essences that are not reducible to mere aggregates of essences). That it is difficult to define certain essences shows nothing. To quote Dr. Edward Feser:

“Of course, whether certain natural objects really should be grouped in the same class or not, and exactly which properties and operations a given object persistently exhibits, might sometimes be difficult questions to settle. Precisely what a thing’s essence is is by no means always easy to determine. But these considerations cast no doubt on the reality of essence...And the point is that the unity and order of things would be mystifying if essence were not a pervasive feature of mind-independent reality.”

Finally unless you are going to adopt a panpsychist world-view, you really have not shown that there are no biological essences (although even if you did, you would not disprove essentialism). I would disagree with Dr. Cundy if when he says that biology is reducible to chemistry, he means “nothing but” chemistry. If he instead means biology is dependent on chemistry, in the sense that plants and animals cannot exist if the molecules that compose them do not exist, then of course I agree with that. But unless you agree that all molecules can sense the world around them (and in a unified way, knowing what other molecules are sensing as well) as the human consciousness does, then you have not done away with animal essences. Even more strong statements could be made once we get into the immateriality of the human intellect. But that is a topic for another post.

6. im-skeptical
Posted at 18:07:34 Thursday December 6 2018


Aquinas would agree that God providentially orders all things with intent, but that is a consequence of his 5th Way, not an assumption. The assumption is that all things act for a certain end or limited range of ends.

- I can't make sense of this. It things are assumed to act for "ends", then doesn't that mean there is a purpose for their behavior? Please note that "purpose" is a synonym for "end". And if there is a purpose, doesn't that imply that there is an intelligence that assigns that purpose. But that intelligence necessarily precedes its assignment of purpose. As I see it, the notion of a God with purpose and intent is the starting assumption, and all of Aquinas' philosophy follows from that.

This does not mean “purpose”.

- Of course it does - by definition. But it's not the rock that has its own purpose. It's the intelligent agent who gives the rock purpose.

So it must be because of its telos or final cause. But for any finite or contingent thing to have a final cause will ultimately require an intelligent agent specifying that final cause

- That agrees with what I said. But to assume that this purpose exists without first assuming God makes no sense at all.

Metaphysics is not supposed to have predictive value except for in a very general sense (things will change, have causes, explanations, etc.). The point of metaphysics is to provide an ontological framework that is consistent with any type of physics.

- You can't separate them. If you believe that there is such a thing as mass or force in physics, then you hold a metaphysical view that these things have some kind of reality that forms the basis of your physics. There is no law stating that there must be only one system of metaphysics, or that what exists in one system must exist in all systems. The concept of force might be perfectly valid in Newtonian physics, and irrelevant in particle physics, for example. But there is no kind of modern physics where act and potency are relevant. They were relevant for Aristotle, but they are now obsolete. That have no role, or explanatory power as a mechanism for change.

That it is difficult to define certain essences shows nothing.

- It certainly doesn't make the case that essences are anything more than a conception in your mind. If you have to go down to the level if the individual, as Dr. Cundy has suggested, then that argues against the very idea that essences exist. Instead, each individual has its own characteristics, and there may be overlap with other individuals, but there is never 100% overlap. So each individual has shared and unique characteristics. The concept of essences is meaningless.

Finally unless you are going to adopt a panpsychist world-view, you really have not shown that there are no biological essences

- I fail to understand what panpsychism has to do with this discussion. Perhaps you could explain.

7. Scott Lynch
Posted at 22:01:33 Thursday December 6 2018

Response to im-skeptical



I am really having a hard time explaining this to you, so I will try to keep things simple.

Please answer yes or no (with no further comments) to these questions.

1. Do you believe that certain particles (like electrons) always (or at least almost always) repel other particles of the same type?

2. Do you believe it is logically possible for a universe to exist in which a certain particle does not always repel a certain particle of the same type? (For example, it might sometimes attract one, or sometimes do nothing, or sometimes repel one, or sometimes be changed into another particle at the presence of one).

7. Nigel Cundy
Posted at 23:13:46 Thursday December 6 2018

Reply to Im-skeptical (post 4)

Sorry I didn't reply early, I have been tied up for a couple of days.

1) Yes, I admitted that my explanation is different from Aquinas (though not so different -- I just add a few intermediate steps). I feel that my explanation is a little more natural in the context of my own wider system (which is not quite the same as that of Aquinas), but both work well enough.

2) The issue here is you are treating "end" and "purpose" as synonymous. But as I have suggested, this is not what Aristotelians would accept. I quoted some passages from Aristotle suggesting that he treated the last step of a physical process as an end, and one from Aquinas suggesting that he would have accepted this, viewing the final cause in physics as essentially the opposite of the efficient cause. [Granted, the concept of telos is a bit broader than this when applied to non-physical applications]. A state of statistical equilibrium would also serve in another sense. Even natural selection drives the genetic pool of a population towards a state that is well adapted to its environment, and that is another form of end in the sense that Aristotle used it. I believe that almost all scholars of medieval philosophy would agree with myself and Scott in this regard. [All that I have read do so -- but, of course, I am not an expert so could be wrong.] This is certainly what contemporary Aristotelians mean when we talk about "ends" or "final causes". So why do you not take us at our word, and keep reading us as though we in fact use a very different definition?

With regards to the passage you cited, the key point evolves around the Latin word "intendo," translated here as intention. This word (if you are willing to accept my rather hazy memories of Latin) is ambiguous in medieval academic Latin; it could mean what we today call an intention, or it could just mean "aims towards," when applied to a mindless object. So I don't think that the example you give is as clear-cut as you suppose. Note that firstly the word intendo applies to the agent here, which is effectively the efficient cause -- it does not mean God. Secondly, the Article Aquinas was asking here was, "Whether it is proper to the rational nature to act for an end?" which explains why he uses the ambiguous term; he wants his "agent" to cover both rational and non-rational agents. The point he is making is the very opposite of what you claim: as is clear from the objections to this article, the subject of debate is whether non-rational beings can act for an end (all being agreed that rational beings can). His wider answer is that all natures act towards an end, but rational and non-rational agents do so in a different manner. Since only rational beings can show purpose, this means that there are types of "end" which don't (directly) involve an intellectual or rational purpose. In the very next sentence after the one you cite, we read:

And just as this determination is effected, in the rational nature, by the "rational appetite," which is called the will; so, in other things, it is caused by their natural inclination, which is called the "natural appetite."

Purpose is associated with will. So Aquinas is here saying that there is another type of end, applicable to other things, which is not related to purpose.

To quote from the Catholic Encyclopedia on the medieval meaning of "appetite",

Appetite includes all forms of internal inclination (Summa Theol., I-II, Q. viii, a. 1; Quaest. disputatae, De veritate, Q. xxii, a. 1). It is found in all beings, even in those that are unconscious. The inclination to what is good and suitable, and consequently the aversion to what is evil — for the avoidance of evil is a good — are included in it. It may be directed towards an object that is absent or towards one that is actually present. Finally, in conscious beings, it is not restricted to organic needs or lower tendencies, but extends to the highest and noblest aspirations. Two main kinds of appetite are recognized by the scholastics; one unconscious, or naturalis; the other conscious, or elicitus, subdivided into sensitive and rational. From their very nature, all beings have certain tendencies, affinities, and forms of activity. The term natural appetite includes all these. It means the inclination of a thing to that which is in accord with its nature, without any knowledge of the reason why such a thing is appetible. This tendency originates immediately in the nature of each being, and remotely in God, the author of that nature (Quæst. disp., De veritate, Q. xxv, art. 1).

This is, of course, just how Scott and I have been defining "final cause", and suggests that Aquinas' use of intendo meant to include either a intellectual will or purpose (for rational agents) or a natural inbuilt tendency (for non-rational agents).

There is always a difficulty when we take take a word from a foreign time and foreign language and try to interpret it using modern definitions. Unfortunately, words change their meaning over time. Which is one of the things that makes reading ancient writers difficult. If your interpretation hinges on one particular word, rather than just relying on the translator, you need to see how that word is used elsewhere in the writer's work and others of his time to try to figure out the range of meanings it had then.

3) You say act and potency as I define it is useless in modern physics. I read that as saying the mathematics of Hilbert spaces is useless to modern physics. Or the solutions of the Time-Independent Schroedinger equation. [I cite these examples because, in my interpretation which perhaps goes a bit beyond Aquinas, these are applications of the concept of potency to particular physical systems]. These alone do not allow us to explain or predict motion. But they are nonetheless important, one for the consistency of the underlying mathematics, and the other to define the possible states of the system, and as a first step to solving the time-dependent Schroedinger equation. While explaining and predicting motion is a big part of physics, it is not all of physics.

4) I wouldn't fully agree that that you have shown that the notion of essentialism is disproven for biological species -- I merely conceded the point because a) I don't consider it that important; and b) It is moving onto areas where I am not qualified to judge whether an argument is successful or not. You would be better off arguing this point with an expert in biology (where I would be an interested spectator). You say that a metaphysical system needs to be general. I agree. But the problem is what does "general" mean here? I would say that it means applicable to every situation, but not necessarily in the same way.

I stated that biology ultimately reduces to physics. As Scott rightly pointed out, most Thomists would disagree with this (I myself, being a non-expert, prefer to keep myself neutral as much as possible -- I overreached in my previous post). However, it is a thesis that I think most atheists and agnostics would accept. As such, I feel justified in applying it in my argument (since if it is not correct, you have a different problem).

I want to make two points. The first argument runs as follows: 1) The concept of essence is, properly translated and mathematicized, useful in explaining all objects described by fundamental physics; 2) It is assumed that everything in nature ultimately can be explained by physics; 3) Therefore the concept of essence is a part of the explanation of everything in nature (including at the level of biological organisms). I have argued for point 1), and you haven't disputed that. I assume that you accept point 2) [If not, I would be interested to know what other factors you would add to the explanation which are consistent with your scientific naturalism.]. So how do you evade the conclusion?

My second point is this: The topic of this debate is "Is Thomism consistent with quantum physics?" Whether or not Thomism is consistent with biology is irrelevant to the topic at hand. It may be that it succeeds in quantum physics and fails elsewhere, in which case it would be consistent with quantum physics but untrue. I would obviously disagree that it is untrue (or at least all the diverse philosophies that have been or could be inspired by Aquinas are untrue: Thomism has grown into a family rather than a single entity). But that is not what we are debating. But if you want to argue that Thomism is inconsistent with quantum physics, you have to start addressing hydrogen atoms and ethanol molecules.

8. im-skeptical
Posted at 17:24:39 Friday December 7 2018

I feel that my explanation is a little more natural in the context of my own wider system (which is not quite the same as that of Aquinas), but both work well enough.

- I'm confused as to what your position is. With regard to a particle that decays spontaneously, is the efficient cause the particle itself, or is it some other thing that supplied the energy for lower-level particles to be assembled together? From a scientific perspective, there is really no point in talking about causation. It gets into all kinds of complexity that destroys any notions about "chains of causality" (as scholastic scholars have described). Instead, we speak about how things behave, according to patterns, or "laws" of physical regularity that are observed in nature. We recognize that "causality" is best seen as a complex network of mutual interactions among things.

The issue here is you are treating "end" and "purpose" as synonymous.

- And rightly so. That's the way it is defined in the dictionary in the context of its usage in discussions about final cause. You mention the difference between the "rational appetite" and the "natural appetite". Sure. But Aquinas still believed that it was God who defines what the natural end is. It is God's purpose for natural things, and is is therefore the will of God and his intellect. I refer you to this article from Aquinas Online: The final cause is the basis of Aquinas' Argument from Design - which assumes an intelligent agent in nature.

I read that as saying the mathematics of Hilbert spaces is useless to modern physics. Or the solutions of the Time-Independent Schroedinger equation.

- Those mathematical devices don't assume or depend on the concept of act and potency. Not in any way, shape, or form. They ARE useful in physics, but act and potency don't serve any useful role whatsoever.

You would be better off arguing this point with an expert in biology

- I think the experts (in the field of biology) are pretty much in agreement.

Therefore the concept of essence is a part of the explanation of everything in nature

- Somehow, I don't think that's exactly what the philosophers had in mind. If you say that essence applies at the lowest levels of fundamental physics, but not necessarily at the level of our every-day human experience of the physical world, then you are missing the boat. Aristotle and Aquinas certainly believed that EVERYTHING has an ideal form with essential properties. Animal species were no exception to this. (And yes, I have read Oderberg on essentialism.) But modern science belies their essentialism. There are many things in the natural world that simply don't fit the essentialist notions of reality.

Whether or not Thomism is consistent with biology is irrelevant to the topic at hand.

- I would agree that biology and many other areas of modern science aren't strictly physics, but as you said, it all boils down to physics in the end. Nevertheless, there are emergent behaviors and properties of things that are best understood and explained at other levels besides particle physics. If Thomism doesn't work in biology or other scientific fields where we explain most of the things we observe in our world, then it seems to me that you are relegating it to a layer of reality that doesn't serve to explain the things in nature that were the subject of Aristotle's science, or the basis of Aquinas' a posteriori arguments.

9. Nigel Cundy
Posted at 19:33:55 Saturday December 8 2018

Response to Im-skeptical (post 8)

I'm confused as to what your position is.

My own view can be visualised in terms of the QED Hamiltonian I wrote in my main post. That describes the various possible fermionic interactions in Quantum electrodynamics. The annihilation operators represent initial states or efficient causes. The creation operators represent final states or effects. [Granted, these are bare operators rather than renormalised, so the full explanation is a bit more sophisticated than this.] This is not what Aquinas himself proposed (or would have proposed, based on his writings, had he understood this physics). I believe my explanation is more natural in terms of QFT. But both the systems I provided are possible applications of the concept of efficient causality to quantum physics.

The philosophical concept of efficient causality is broad, and covers many different possible physical theories. But in each theory there is something which is the application of efficient causality to that theory. In QFT, the initial states of a physical process are the efficient cause, as applied to that theory. As I keep saying, physicists do use and presuppose the medieval concept, but just call it by a different name.

And rightly so. That's the way it is defined in the dictionary in the context of its usage in discussions about final cause.

Scott, I, and other more well known Thomists such as Feser, Oderberg, Gilson and so on have repeatedly said what we define final cause to mean when it is applied to inanimate objects. And it is that definition we use in our arguments. Why do you keep trying to force your definition, equating final causality with purpose, on us? Final Causality has been generally equated with purpose for both animate and inanimate objects since the enlightenment. As I said earlier, I believe the idea was introduced into Western thought during the Renaissance (following a rival school of Greek/Roman thought to the neo-Platonic/Aristotelian tradition which dominated Christian thought until that time) -- though I would accept correction from a historian of philosophy (or at least their evidence). But the meaning of the term in the neo-Platonic and Aristotelian tradition was different from what has been used since the enlightenment.

There are two issues here:

1) The historical issue.

2) The issue of how final causality is used in the arguments of contemporary Thomists and representations of Aquinas' thought.

With regards to the first point, I have cited several historical sources, both classical and medieval, to support my argument that as applied to medieval physics final causality was not equated with purpose. You have now presented two sources, one medieval, one modern, and as I have shown/will show, when read in full they also support my position.

The second point is perhaps more important. In practice, I don't care about offending dead people by messing up their definitions. What I care about are arguments, and whether they stand up to scrutiny. I outline the fifth way in detail in my book (mainly to show that post-enlightenment responses to the argument from design are useless against it). I then use my definition of final causality as the basis of a slightly different argument (which is the one I use). Edward Feser has also defended the fifth way using what he and I take to be Aquinas' definition of final causality as its premise. You can't substitute your own definition, even if it is widely held by post enlightenment philosophers, into somebody else's argument, and claim that you have correctly represented that argument.

Now, onto the source you cited.

The final cause, according to Aristotle is that for the sake of which motion happens. It is the end or purpose for which the motion takes place. Again, it is easy to understand this doctrine if one considers motions which humans initiate. A sculptor sculpts in order to produce an staute, which he might do in order to make money. In nature, the final cause is not external to the thing that acts, but internal. Fruit does not grow to be food for humans and animals, but for the sake of generating another tree. Thus, typically, in generation, the final cause is the full actualization of the form, i.e. the mature adult of whatever species is generated.

So as with the previous example you gave from Aquinas, there is a distinction made between rational agents (humans in this example) and inanimate substances (the in nature in this passage). Rational agents have a will (indeed related to what we now call purpose) and final causality is manifested in them in one way. Inanimate substances do not have a will (obviously), but nonetheless are observed as acting towards certain ends (a tree naturally grows fruit, which in turn generates new trees). Those ends (and this is the key point in Aristotelian philosophy) are not imposed on it by an external being (which could include something with a will), but are internal to it and part of its nature. Thus final causality in inanimate substances -- the things that are studied by physics -- is not related to purpose.

The fifth way is not an argument from design (even though the common English translation uses the word "designedly", Aquinas means a different thing by the term). In many respects it is the very opposite of such an argument. The argument from design is an argument by analogy based on the harmony of the parts of various natural organisms. The fifth way is not an argument by analogy, and it works just as well for both harmonious and disharmonious physical systems. It [I am paraphrasing here] starts with the premise that inanimate objects act towards certain ends according to their nature. This action towards certain ends can be thought of as a law of those natures [a law of physics, but not a mechanistic law of physics as the term was understood in the early modern era]. However, the chain of explanation summarised by this law cannot originate in the things themselves, because there is nothing in the concept of prime matter which could initiate it to change in certain ways but not others, and nothing in the concept of form which is capable of actualising such a change. [Final causality refers to the observation of this tendency, we are seeking the explanation for the tendency.] Indeed, it cannot ultimately originate in any material thing, so it must be immaterial. The law nonetheless represents a sense of directionality. In an immaterial being, the only thing that imparts directionality is a will (follows immediately from the Scholastic definition of a will). Therefore, there is an immaterial will which directs every [I acknowledge that I need to do a bit more arguing to justify that "every", but it is a bit much for a blog comment] natural change. Since this immaterial will "understands" the abstract notion of form (so it can direct the initial state to those effects), it must also sit alongside an intellect (from the scholastic definition of intellect). We can define the word "God" to represent this combined immaterial will and intellect, and a bit of further argumentation shows that this "God" is the same as the "God" defined as the termination of the cosmological argument. That at least, is a quick paraphrase of the argument in the fifth way, hopefully not too badly misstated. Edward Feser (and other Thomists as well) have expounded it better than I am able to here. As Scott and I have stated, Aristotelian final causality, as we have defined it, is the premise of the argument. The conclusion is that there is an immaterial will that guides everything. I hope you will agree that this is not an argument from design, as used by Paley or modern creationists. But final causality is still defined as that inherent tendency towards certain effects seen within inanimate substances.

Those mathematical devices don't assume or depend on the concept of act and potency.

They are the concept of potency, as applied to the framework of quantum physics. That is what I have been repeatedly trying to argue.

But in any case, you missed my point. You argued that the concept of potency was irrelevant to modern physics because it does not explain motion. This response is built on the premise that the only things relevant to modern physics are those directly involved in the explanation of motion. I cited a couple of things that are very relevant to modern physics which equally are not directly involved in the explanation of motion. You have now agreed that these things are relevant to modern physics. Therefore, you accept that not everything important to physics is directly relevant to the explanation of motion. Thus your premise is refuted, and with it your response several posts ago to my earlier argument.

But modern science belies their essentialism. There are many things in the natural world that simply don't fit the essentialist notions of reality.

I agree that there is an issue for Thomism here (although perhaps it has been resolved, and neither of us are aware of that). And I agree that Aristotle was largely inspired by biology. I disagree that it has been proved that there are many things in the natural world that simply don't fit the essentialist notions of reality. I agree that you [well, not just you] have raised questions that might suggest that there are such things. And I agree that those questions need answering. But you have just stated the problem. You haven't taken the effort of proving it (that is to say, started from each of the various possible definitions of essentialism -- or even just those consistent with Aristotle -- rigorously worked out all their implications for biology, and shown that they are inconsistent with evolution). I agree that the onus is on my side of the debate to provide a response for you. But I am not the person to do that, because I don't have the experience or knowledge necessary. I have ideas, but (as we have already seen) they are not by themselves enough, and at best need to be fleshed out by an expert (i.e. a Thomist or related philosophical tradition who has studied biology) and at worst abandoned completely. That I can't come up with a reasonable solution doesn't mean that there is no solution.

But I am an expert on quantum physics, and am qualified to address the issues here. I strongly believe that some form of Aristotelian philosophy is pretty much the only real option for a working philosophy of quantum physics, and, by extension, most of the rest of physics and chemistry. I agree with you that a metaphysics needs to be able to encompass everything, including biology. But it also needs to encompass physics. So I could invert your argument, and debate that whatever your non-essentialist philosophy of biology is, it is inconsistent with fundamental physics, which implies essentialism.

Maybe my philosophy of physics needs expansion to allow it to apply to other fields (I wouldn't be surprised if it did; I am applying the concepts to a very narrow field). Maybe we have to reduce the biological essences to very broad categories (animal, vegetable, bacteria, rational, ... -- I would regard this distinction as the minimum required for Aristotle's philosophy). Note that in Aristotle's system, each of these categories is defined in terms of their inherent natural tendencies, i.e. reproduction, common to all life, in animals self-movement, in plants photosynthesis, and so on.

To take up the example I used before, rationality, which I defined as the ability to make abstract representations of things, such as in artistic or mathematical expression [and which animals except ourselves, have, in the wild, ever painted, made sculptures, or solved a quadratic equation?]. You stated that this ability was shown to have developed gradually, in a continuous change.

Of course, firstly, biological evolutionary change is never continuous, because DNA uses a discrete language. We are discussing small changes in genetic code. As I am sure you are aware, a small change in the DNA can lead to a very large change in the resulting organism. I know that in physics there are phase transitions. First order phase transitions, where a tiny change in one parameter leads to a discontinuous change in an effect; second order phase transitions where the differential of the effect is discontinuous when the initial parameter changes infinitesimally, and so on. Clear boundaries between species would be analogous to a first order phase transition -- a single small mutation creating a gigantic change in the organism. We can also think of second order transitions, where a single small mutation changes from a state where none of the ancestors had the tendency, to one where all the descendants exhibited that tendency in gradually increasing amounts. Once again, that transition could stand as a clear boundary between species.

Certainly the development of rationality must have been at least a second order transition. If our ancestral lineage started with a single celled organism, which spawned more single celled organisms across innumerable generations, none of which were capable of any thoughts let alone abstract ones, and then there was a change which gradually allowed the ability to think, and then think abstractly, in the being's descendants; imperceptibly at first, but then increasingly more obviously until you reach us, there is still a phase transition and thus a natural boundary between the two different species (using this very broad definition of species).

Or we can modify essentialism so that it allows for fuzzy borders between species. We can say that this is clearly a rational animal, with certain inherent natural tendencies. That is clearly a vegetable, with another set of inherent natural tendencies. Somewhere down the chain of ancestors, we find something that is neither clearly one nor the other. Fine; that doesn't change that today's animal or today's vegetable have clearly distinct tendencies. That ancestor would simply sit on the boundary between the two, either in both species or a species of its own.

10. im-skeptical
Posted at 17:36:36 Sunday December 9 2018

But in each theory there is something which is the application of efficient causality to that theory. In QFT, the initial states of a physical process are the efficient cause, as applied to that theory.

- I would argue that if it is questionable as to exactly what the efficient cause is in some particular case (or if it doesn't really matter), then that's not a very good concept to use as a metaphysical basis for physics.

With regards to the first point, I have cited several historical sources, both classical and medieval, to support my argument that as applied to medieval physics final causality was not equated with purpose.

- I quoted Aquinas himself, who said that it was the "intention of an end" That sounds purposeful to me.

there is a distinction made between rational agents (humans in this example) and inanimate substances (the in nature in this passage).

- The distinction made by Aquinas (as I read it) is that one is the intention of man, and the other is the intention of God.

Therefore, there is an immaterial will which directs every ... natural change. Since this immaterial will "understands" the abstract notion of form (so it can direct the initial state to those effects), it must also sit alongside an intellect (from the scholastic definition of intellect). We can define the word "God" to represent this combined immaterial will and intellect

- So God's will determines the "end" toward which the final cause is directed in the case of natural things. And you argue that this is not a "purpose"? Are you saying that God is not a rational agent?

Aristotelian final causality, as we have defined it, is the premise of the argument. The conclusion is that there is an immaterial will that guides everything. I hope you will agree that this is not an argument from design, as used by Paley or modern creationists. But final causality is still defined as that inherent tendency towards certain effects seen within inanimate substances.

- It is the design of how things work - not so much the design of the thing itself, although I do believe that Aquinas would have agreed with Paley. In any case, if the premise is final causality, that certainly is based in the notion of God as the "immaterial will" that directs it. That notion is built into the concept of final causality. There is no final causality without that will. So the conclusion of God is nothing but circular reasoning. As much as you want to believe that this is not a circular argument, I can't see how you could presume final causality without first assuming God.

This response is built on the premise that the only things relevant to modern physics are those directly involved in the explanation of motion.

- My position is that for any particular system of physics, there are metaphysical concepts needed to provide a basis for it. The same set of metaphysical concepts are not used in Newtonian and quantum physics. So the metaphysics is different for those things. I think your assumption that there must be universal metaphysical concepts that underly all physics is just an attempt to make Thomism relevant where it would otherwise not be. I repeat: These Thomistic metaphysical concepts play no role in modern science.

Or we can modify essentialism so that it allows for fuzzy borders between species. We can say that this is clearly a rational animal, with certain inherent natural tendencies. That is clearly a vegetable, with another set of inherent natural tendencies. Somewhere down the chain of ancestors, we find something that is neither clearly one nor the other. Fine; that doesn't change that today's animal or today's vegetable have clearly distinct tendencies. That ancestor would simply sit on the boundary between the two, either in both species or a species of its own.

- You can do that, but as a basis for scientific understanding, essentialism only serves to muddle the issue. Essentialism is a reflection of man's natural tendency to classify everything. While that is useful in many circumstances, it can also get in the way of a deeper understanding, particularly in areas like biology.

11. Ficino
Posted at 15:45:06 Monday December 10 2018

Hello Nigel, do I understand you correctly that in ancient and medieval thought, "final causality" did not imply purpose, though in some contexts, additional premises could generate a claim about purpose? You write this:

"Final Causality has been generally equated with purpose for both animate and inanimate objects since the enlightenment. As I said earlier, I believe the idea was introduced into Western thought during the Renaissance ... But the meaning of the term in the neo-Platonic and Aristotelian tradition was different from what has been used since the enlightenment... I have cited several historical sources, both classical and medieval, to support my argument that as applied to medieval physics final causality was not equated with purpose."

I agree as far as Aristotle goes. And in the Fifth Way, Aquinas gets to purpose only in the second half of the argument. But isn't it true that over the stretch of all his philosophical work, Aquinas in fact holds that in nature, all finality ultimately achieves divine purposes, that God is the craftsman in and behind nature? And Aquinas attributes that view to Aristotle. Cf. Comm. Physic., lib. 2 l. 14 n.8: “And so it is clear that nature is nothing other than the rationale of a certain art, namely, the divine art, instilled in things, by which the things themselves are moved to a determined end, just as if a shipbuilder were to be able to bestow on the timbers that by which they could move themselves to take on the form of a ship.”

So, like im-skeptical, I'm having trouble finding space in Aquinas' thought for a notion of finality in nature that is NOT aiming at a divine purpose - even though I agree that within the first lines of the Fifth Way, a purpose of a mind has not yet been demonstrated.

12. Scott Lynch
Posted at 18:06:53 Monday December 10 2018

I think we are going in circles

Dr. Cundy,

I think there is a point where you have to realize that some people (like im-skeptical) are going to be willfully ignorant and obstinately refuse to accept your definitions because they do damage to their own preconceived notions. This is simple confirmation bias in action.

Anyone who thinks that an entire 750 year long intellectual tradition (and in reality a 2300 year long tradition) was founded on an obvious bit of circular reasoning that a sixth grader could refute is clearly not listening with an open, much less charitable, ear.

Considering that the blog in which im-skeptical’s article was posted has a tag line which says “Speaking out against bullshit”, which does not exactly give the aura of disinterested academic pursuit, I would say that any additional comments you make are going to continue to fall on deaf ears and simply waste your valuable time.

To other commenters who are interested. Read through these comments (Dr. Cundy and mine) as there should be enough in there for you to glean the Aristotelian-Thomistic views on final causality.

If you would like additional information on teleology, I would recommend looking up Dr. Edward Feser’s paper “Teleology: A Shopper’s Guide”. This gives a synopsis of multiple perspectives on teleology (final causality for Thomists) including from the Thomistic perspective.

13. Red
Posted at 11:49:42 Tuesday December 11 2018

Hello Dr. Cundy,

I am really enjoying these posts on Thomism and modern physics your points are well argued.

There is this one criticism of Act/Potency from point of view of physics that I've seen in contemporary philosophy I would like for you you look at sometime.

Naturalist Neo-Aristotelian philosopher Rögnvaldur Ingthorsson is working on a project named "Scientific Essentialism: Modernising The Aristotelian View". Although he doesn't seem to engage Thomistic philosophy directly or use quite the same terms, he is working in contemporary Neo-Aristotelian framework of talk about Powers and Dispositions. I think his points does still apply to it.

His point is that act/potency distinction implies a unidirectional view of actions but this view is scientifically falsified because and I quote "However, according to modern physics, unidirectional actions do not exist; all interactions are perfectly reciprocal (Resnick, Halliday & Krane 2001)"

He seeks to revise Aristotelian metaphysics without this particular view of causation.

You can read detailed description of the project here:

His brief paper containing the argument against Act/Potency view

And here he presents his detailed account of causation

14. Scott Lynch
Posted at 14:56:50 Tuesday December 11 2018

Response to Red


I will leave the main response to Dr. Cundy.

I would like to quickly point out that while act/potency does allow for unidirectional causality (in the case of God acting on the world or human free will, for example, it does not require it.

If two billiard balls are rolling towards each other and then they make contact and both stop (due to a cancellation of momentums), they are still actualizing each other’s potentials for rest.

To say that all causality must be unidirectional would seem to violate the conservation of energy. That is simply not an assumption of Aristotelian metaphysics.

15. Red
Posted at 20:06:20 Tuesday December 11 2018

Response to Scott Lynch


Yes, that is one of first point that came to my mind too but read that "causal production as interaction" paper I linked to above on page 11 he addresses that point when he says and I quote:

"It is clear that the standard picture needs to be modified in order to include the reaction of the ‘patient’, although it is still unclear whether this changes anything much, since it is still possible to hold that the reaction is only an effect of the action. That is, even if it is admitted that there are no actions without a reaction, then it can be argued that the reaction itself is produced, or provoked, by the action, and therefore counts as part of the effect produced by

the action."

Then he illustrates the same point through example of brick breaking window, he gets into somewhat detailed discussion but his main response seems to be to point out

"classical mechanics does not consider interactions as being composed of

ontologically different kinds of influences, an ‘action’ and a ‘reaction’, of which one kind is only a response to the other.In mechanics, the terms ‘action’ and ‘reaction’ are indeed considered only to reflect the subjective aspect under which the scientist considers the interacting objects, i.e. as depending on which changes the scientist is interested in; the changes in the window, or the changes in

the brick.........

......In classical mechanics, as paraphrased by Bunge, "physical action and reaction are, then, two aspects of a single phenomenon of reciprocal action."([1959], p. 153)."

Now this sort of reply seems confusing to me and it seems this whole criticism doesn't really address act/potency distinction properly, like how it is used to analyze change or can change be made sense of apart from it.

16. Nigel Cundy
Posted at 22:36:45 Sunday February 10 2019

Response to Red

Sorry for not replying to this comment earlier; somehow I missed it when it was first posted.

The first thing that comes into my mind is whether the idea that physics is based on mutual interactions is actually correct. Unfortunately, I can't access the original argument: the reference is to a physics textbook which I don't have. So what I am going to write is based on a guess of what it is going to be. Ingthorsson only discusses classical mechanics, and this makes me suspicious that the argument is based only on forces in classical physics.

I agree that in classical physics, interactions are reciprocal. Newton's third law comes to mind for contact forces. In Newton's theory of gravity if there are two bodies, then simultaneously and instantaneously A exerts an attractive force on B while B exerts a force on A. I can quite see that in this context, the idea of labelling one as an agent and the other as something being acted on is problematic to standard discussions of causality. A similar picture holds in electromagnetism.

My answer to this form of the objection is going to be that classical mechanics has been superseded.

I'll start by taking a look at non-relativistic quantum mechanics. Here things are governed by the Schroedinger equation. This describes the evolution of a single particle wavefunction. This is described by two terms. The first is a kinetic term (which is related to the idea of inertia in classical mechanics). The second is a potential term. Here one just substitutes in the classical potential. So the equation for particle A will contain a potential that depends on the difference in location between A and B, while the equation for particle B will contain a similar potential term. These two equations are coupled, but I think that it is still true that the interaction is reciprocal: Both A and B both simultaneously see the potential caused by the other particle. So I think that the objection is also reasonable in non-relativistic quantum mechanics.

So now let's think about special relativity. This is where things start to unravel for the classical picture. In special relativity, information doesn't travel faster than the speed of light. The interaction between particles isn't simultaneous. Instead particle A feels the force from particle B as it was a short time earlier, while particle B feels the force from particle A as it was a short time earlier. This changes things a bit, because A can now be identified as the cause of the force on B, while B can be identified as the cause of the force on A. I'm not sure that the problem has gone away completely, but it has been changed.

Now onto general relativity. Here things get even more confused. The particles don't interact directly with each other. Indeed, the whole notion of gravitational force is made far more complicated. Essentially, each body warps space time. They then travel along geodesics of the space time (a geodesic is defined as being tangential to the surface at each point; for example the equator is a geodesic of the spherical geometry which describes the earth). The orbits of the planets are then not caused by forces as Newton understood them but by the principle of inertia. Particles still travel in space lines unless acted on by an external force, but what is meant by a "straight line" is a far more complex question in more advanced geometries. So rather than reciprocal motion, both A and B curve space time, rather than interacting with each other, and then travel according to their natural motion.

But, of course, it is quantum field theory where the idea of reciprocal interaction really breaks down. Consider the basic electromagnetic interaction. We start with an electron. It emits a photon and the electron moves to a different energy state. Here we can clearly represent some agents (the initial electron) and effect (the photon and electron in the final state). There cannot be reciprocal interaction because the photon did not exist in the initial state. Similarly, in the context of photon absorption: we clearly have an agent (the photon) changing the state of the effect (the electron). There is no reciprocal interaction because the photon doesn't exist in the final state.

Or electron/electron scattering. One electron emits a photon. This is absorbed by the other electron. Clearly, in this case, the interaction is unidirectional.

I'm trying to think of a way that the objection can be sustained in QFT. The only thing I can think of is that interactions are reversible. So if an interaction with A as the initial state and B as the final state is possible, then so is an interaction with B as the initial state and A as the final state. However, each individual interaction has a clear direction.

The second possibility is that we don't know which one of the two electrons emitted the photon and which one absorbed it. We only see the initial state and the final state, not what happens in the middle. When we calculate the amplitude, we have to include both possibilities since we don't know which one happens. But that doesn't change that in reality something happens; so in reality one of the electrons is the cause and the other the effect.

So I think that the argument breaks down because it is based on an outdated physics. It arises from the mechanistic principle that the corpuscles can't be created or destroyed. If this were true, then interactions could only be reciprocal. But in QFT, every interaction involves the creation or destruction of at least one corpuscle. In this case, no interaction can be reciprocal.

17. Red
Posted at 08:15:03 Wednesday February 13 2019

Thank You for your input Dr, Much appreciated.

I was a little surprised that this seemingly simple yet confusing objection isn't really discussed in A-T literature that I'm familiar with.

21. www
Posted at 14:34:42 Thursday July 18 2019

Thanks for sharing your thoughts on physics.


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