The Quantum Thomist

Musings about quantum physics, classical philosophy, and the connection between the two.
A Universe from Nothing? Part 6: Where do the laws come from?

Classical theism podcast.
Last modified on Sat Dec 21 22:25:09 2019

If you haven't yet done so, then please pay a visit to the Classical Theism Podcast. It is a great resource, with numerous interviews with some of the leading contemporary thinkers and apologists for classical theism and classical philosophy.

I wouldn't describe myself as a leading thinker, but John De Rosa also contacted me a little while ago to see if I could have an interview with him. The interview will be posted on December 23rd 2019. We had a good discussion. Topics included why I became interested in classical theism, why I included a chapter on ethics in a book about the philosophy of science, and my work on reconciling an Aristotelian philosophy with contemporary physics.

Probability, Fields and Bell's Theorem

Reader Comments:

1. John Not Real Name
Posted at 14:07:47 Monday December 23 2019

Today is the 23.12.19!

Today is the day but when are they going to put it up as most of the Catholic revival is going on in the United States of America so time zone issues.

Thank You for your content Dr Nigel Cundy (I have a weird obsession with writing out the full names of people or places e.t.c. please bear with me).

2. Scott Lynch
Posted at 18:11:16 Saturday December 28 2019

Great Interview!

Yes the book really was a fantastic read. The section on ethics was an unexpected gem. Excellent refutation of utilitarianism and the Humean is/ought objection.

I really wish John DeRosa had a chance to talk to you about the unicity of form, specifically, what you say in your blog and book about how the Hamiltonian of a water molecule is not a linear combination of the Hamiltonian of hydrogen and oxygen. I would love to see an entire blog dedicated to fleshing that our for us non-specialists. Of course I am sure your plate is full. Even a link or two in lieu of that would be great.

3. Tim S
Posted at 19:54:19 Sunday December 29 2019


Just wanted to alert you (if you aren't already aware) of a unhelpful comment from a person named Mat. I think it is either worth addressing or deleting. It is on the relationship bill post. I might have a different view than you, but I'd delete or respond to it.

4. Nigel Cundy
Posted at 17:39:13 Monday December 30 2019

Relationship bills post

Thanks Tim. I had missed that post. I don't like deleting comments which aren't obviously spam or abusive, so I will have to make a brief reply.

5. Will Worrock
Posted at 04:37:15 Sunday January 19 2020

Dr. Cundy, I have been reading your blog recently and have become a big fan. I have a question, however. According to Thomistic metaphysics, what are the different types of motion? Because in all the examples I can think of are examples of local motion. What are the other kinds?

6. Nigel Cundy
Posted at 18:02:15 Sunday January 19 2020

Motion that isn't from place to place

Motion (in Aristotle's system, or at least my understanding of Aristotle, which might not be the same thing) is any movement from potentiality to actuality. I ought to explain that a bit.

We know that things can change in some respects and yet also remain the same being. The way to think about this is to say that a being can exist in numerous different states. So, for example, if I move my finger, we can describe the original arrangement of atoms as one state (state A), and the final arrangement of atoms after I have moved my finger as a different state (state B). I am the same being, but two different states. These states correspond to the different potentia of the being. So initially, I am actually in state A but only potential with respect to state B. Afterwards, I am actually in state B, and in potential with respect to state A.

That is just intended as an illustration. In practice, the concept of state is far more general than just arrangement of atoms (obviously, since Aristotle himself wasn't an atomist). States can be distinguished by location, but they can also be distinguished by other things, such as spin (speaking in the particle physics sense, where the word does not mean "rotation"). A fermion can flip its spin without change in its location or momentum (for example by emmiting a spin 1 photon and absorbing a spin 0 Higgs boson with the same momentum). An example which is frequently used is a cup of coffee which is actually hot and potentially cold (as well as all the intermediate states between hot and cold). "Hot" and "cold" refer to two different states. The cup of coffee doesn't change its location, but there is still motion from a hot state to a cold state. This is one classic example of motion which doesn't involve change of place as used by contemporary Aristotelian philosophers. Other examples would include a change in colour.

Yes, but you are now probably saying that temperature in a cup of coffee is ultimately related to the average kinetic energy of the individual molecules in the coffee, which is tied to how fast they are travelling, and thus comes back to local motion. I think the usual answer to this would be that the substance we are considering is the coffee as a whole, not the individual molecules. The coffee as a whole doesn't change its location. Temperature only makes sense when we consider an ensemble of particles, in some way linked together.

We can also consider quantum systems as another example (and in my view a more pertinent one). For example, the energy bands in a metal spread out across the whole substance. All the energy bands. To say that an electron is in a particular energy state thus says nothing about its location; because it is in a definite momentum state, the location is undefined. Two different energy states would thus equally be spread out across the whole metal. When an electron moves from one state to another, there is no real local motion. The temperature of the metal is again a measurement of the average energy of the particles. When the metal is cold, it means that the electrons are in the lowest energy state possible. As the metal heats up, the electrons on average move to a higher energy state. We can't tell which energy state any given electron would be in from the temperature of the metal; once again it is a quantity that only is only defined in terms of the metal as a whole. Also, unlike the cup of coffee where the bonds between the molecules are very weak and we can treat the cup of coffee as a collection of objects rather than a single object, in the case of the metal, the binding energy is strong. We thus use an effective Hamiltonian prescription to describe it, which combines the underlying operators describing the valence electrons and the atoms into a different mixed basis. The electrons are in this respect subsumed into the metal as a whole. So here we have a clear example of something which undergoes a change in state (from hot to cold) without a movement from place to place, or even a change in the way things move from place to place.

7. John Not Real Name
Posted at 14:40:09 Monday January 20 2020

New Breakthrough?

I received an e-mail from my Physics teacher on Quantum-Physics and the link was to this article by Nature ( ) in which the issue of quantum entanglement and Einstein's contention of "spooky action at a distance". The paper has not been peer-reviewed however many are already excited. It is 165 pages (PDF) so it seems like a tough topic and my amateur understanding means I am not privy to the excitement that is apparent in the Scientific Community. Please enlighten me.

Thank You.

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