What are Laws of Nature?

[dga471 (Daniel)]

@vjtorley

Either a thing exists or it doesn’t. Virtual existence is a cop-out.

Feser would say that for something to to exist virtually in a substance means to be in it potentially, in fact in a stronger sense than in a purely potential sense (as all substances exist potentially in prime matter, but hydrogen and atom exist potentially in a stronger sense in water than in prime matter) (Feser, Aristotle’s Revenge, p. 336). It seems to me that Thomists think there are many different substances, all of which have very different and complex potentialities due to the things existing virtually in them.

Secondly, even if you think this is a cop-out, it appears to me that there’s nothing really wrong with saying that hydrogen and oxygen don’t exist in water. It would be similar to an instrumentalist point of view, where scientific notions are merely useful mental constructs to characterize experimental predictions and results. We model a molecule as a collection of atoms linked by chemical bonds because that is the best way to predict certain properties. An instrumentalist point of view is not uncommon among philosophers of science in general.

@vjtorley

Water is composed of hydrogen and oxygen atoms , which retain the micro-level properties of hydrogen, even if they lack the macro-level ones which we commonly associate with this substance…Whether hydrogen atoms will react with oxygen depends on what (if anything) they’re bonded to. While free-floating hydrogen radicals are highly reactive, hydrogen atoms which are already bonded to oxygen in a water molecule are obviously less so. But that doesn’t make them something other than hydrogen.

I think this is less clear-cut than you think. When hydrogen and oxygen atoms form into a water molecule, they generate a new set of energy levels that are different from hydrogen or oxygen. This is why the emission spectra of water is different than that of hydrogen or oxygen. You cannot experimentally “access” the hydrogen or the oxygen molecule “directly” while they are still in the form of water. (Although maybe some chemists could correct me.)

@vjtorley

But in A-T metaphysics, “system” is not the name of any kind of natural entity, such as a horse or a palm tree. There is no substantial form of a system, as such. Hence it lacks a nature. Do you see now why I am perplexed?

You can replace the word “system” with “substance”. Most of the things we mention here are not (in the Thomist parlance) artifacts, but natural substances. Electrons, atoms, molecules are all natural substances (or existing virtually in them) which can have symmetry properties that cause them to be relevant to Noether’s theorem.

@vjtorley

But it strikes me that quantum fields could be said to perdure through time: they’re always there, even if particles are continually popping into and out of existence. Thoughts?

I can’t find the relevant passage in Scholastic Metaphysics, can you quote a little bit of the context and surrounding sentences?

My first reflex is to point out that the terminology is not quite right. In quantum field theory (QFT), particles are oscillations of quantum fields. As the fields oscillate, they “change” (although you should ask a real Thomist about whether I’m using the word change correctly, in an A-T sense).

Interestingly, I have seen Thomists point to neutrino oscillation as an example of how even fundamental particles can change.

@vjtorley, I think these are all good questions. Keep them coming - I’m going to be attending a 4-day seminar on Thomism where there will be a lot of Thomists around to ask questions. The topic this year happens to do with flux and change!