I’m not sure I understand matter

Catholic thought has been deeply entwined with Thomism for centuries and while the association has loosened it is still very present.  So as a reactionary Catholic I’m of course sympathetic to that philosophy.  But the truth is, my understanding of it is quite deficient.  I have read parts of Thomas’s and Aristotle’s  works and some popular explanations but not enough for a full understanding.

Typically I read up on some questions I’m interested in until I can make sense of it. But that’s basically using famous works as a quarry, gathering material to patch up my thinking.  I’m not really interested in what Aquinas said because he said it, but because it is often true.  At least for a layman like me, that seems like a reasonable way to do it.  But sometimes I’m not sure if I understood the original answer or just reinterpreted some proof-texts to mean an answer that makes sense to me.

One example where I’m unsure if my interpretation fits the original system is matter. It probably doesn’t mean what we call by the same name in modern physics, but then what does it mean? I tend to look at this by looking at the function the concept serves in the original context and then trying to figure out if I know of anything serving that function in reality.

So one reason to talk about matter and the related concept of form is explaining creation and destruction. Consider, for example, a paper clip. If I bend it out of form I have a piece of wire that is no longer a paper clip. It may also be melted down and remolded into some other object. In both cases the paper clip as such ceases to exist. But I still have a new object made of steel and in fact made of the same steel the paper clip was previously made of.  Now we just stick a label on it: What perished gets called the form and what survived gets called the matter of the paper clip. The paper clip was made up of both and that kind of combination gets called a substance^[1]. So in our example the matter of the paper clip is steel and the form might be something like “a thin, kinked wire forming two loops elastically connected”.

One consequence of this is that what matter is in any given context depends on the substance we’re analyzing. For example, a chunk of steel is the matter of the paper clip, but that chunk of steel is itself a substance composed of form and matter. The matter would be atoms of iron and carbon and possibly some others and the form would concern, for example, the crystal structure and such things. This relativity is, I think, what the distinction between proximate and remote matter is getting at.

The extreme end of this continuum would be matter devoid of any form, which is called prime matter. Prime matter as such can’t exist or even be imagined, because it is, by definition, the pure potential to exist in some form. Basically neither forms nor prime matter directly exist, they are rather aspects of the substances that do directly exist.  Fitting either to objects known in, say, modern physics would be missing the point.

So far I’ve just been parroting the standard definitions, now I’ll try to apply it and possibly prove I don’t really get it: How far down the chain can we actually go? What is, so to say, the maximally remote matter actually existing? The knee-jerk answer would be elementary particles, but I think that is wrong. The problem is that elementary particles can sometimes be created and destroyed. The canonical example would be photons, that is the particles of which light is made of. The screen I’m presently staring at doesn’t have a reservoir of photons, it (or some part in it) is creating them as it sends them to me. And then they hit my retina and cease to exist. But they don’t simply appear and disappear without trace. They do, for example, carry energy from the screen to my retina. And I think in this framework that would make the energy part of their matter^[2]. The photons are made of energy, that energy exists before and after them, so it is pretty much by definition matter in relation to them.

But how can I say the energy survives the end of the photon? Whatever absorbed the photon doesn’t keep the energy around separately, it just gets added to the energy it already has.  I think the answer is that energy is conserved, i.e. the total amount of energy is the same before during and after the photons existence. But then I could make the same argument for other conserved quantities. So, for example, charge and spin would also be maximally remote kinds of matter in the metaphysical sense. I’m not so sure I can extend the same treatment to vectorial quantities. I thought, for example, about momentum  being a kind of matter, so that a substance being in motion would be equivalent to it being conjoined to the motion kind of matter. The problem with this interpretation is that two frontally colliding objects with momentum \(p\) and \(-p\) stop. Total momentum is conserved, because it was \(p-p=0\) before the collision and is \(0+0=0\) after it.  But the momenta of the two objects cease to be and that is not something matter should do^[3]. So my best guess is that the maximally remote kinds of matter actually existing correspond to scalar conserved quantities. Nice slogan, eh?

Now the question is, could a Thomist who really knows his stuff agree with that?  And the answer is I don’t know. My understanding is compatible with the usage of the word matter in all arguments I know of, but then I obviously don’t know all arguments. So maybe the real Thomist would tell me this is bunk because of some extremely well known text I missed.  On the other hand maybe he would dismiss it as trivial stuff every serious metaphysicist knows about. So I have an understanding of matter and it serves me, but I’m still not sure I actually understand what other people meant by matter.