Hi @dga471,
Still, what’s interesting to me is that most Aristotelian-Thomists tend seem to hold the view that these lower-level entities don’t actually exist in the real world, because they always combine with each other to form new substances which have their own causal powers…The classic example is water - a Thomist would typically say that hydrogen and oxygen don’t really exist in a molecule of H2O - they only virtually exist. Same goes with protons, neutrons, and electrons, which only virtually exist in the oxygen atom (which is itself, also only existing virtually in the water molecule). This virtual existence goes all the way down to quantum fields.
I have to say I have a problem here. Either a thing exists or it doesn’t. Virtual existence is a cop-out. According to Thomists, I have one and only one substantial form, and when I die, my corpse has another form entirely. The only thing in common between me and my corpse is prime matter, which is pure passive potency, devoid of any positive characteristics at all. So by rights, there ought to be nothing in common between me and my corpse - and yet they both have the same shape, size and mass (at least, immediately after my death, they do). Thomism doesn’t provide a good explanation of this fact.
Likewise, the suggestion that water is not composed of hydrogen and oxygen is frankly absurd. If it’s not composed of hydrogen and oxygen, then what the heck is it composed of? What are you going to call the two smaller atoms in a water molecule, if you’re not going to call them hydrogen atoms? Thomist arguments purporting to prove that water isn’t composed of hydrogen and oxygen are weak. I’m looking at Ed Feser’s Scholastic Metaphysics, page 178. Feser quotes an argument by Professor David Oderberg, that if water contained actual hydrogen, we should be able to burn it - but in fact, the opposite is the case. However, this argument only shows that water is not composed of hydrogen and oxygen molecules - but then, who said it was? 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. At standard temperature and pressure, hydrogen is a nontoxic, nonmetallic, odorless, tasteless, colorless, and highly combustible diatomic gas with the molecular formula H2. 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 don’t think that Noether’s therem presents special difficulty to the Aristotelian. It is more of a mathematical theorem which is necessarily true given certain conditions. Why some physical objects behave in that way (i.e. having a symmetry in its Lagrangian, which by Noether’s theorem implies a conservation law) is the question. It could be in the “nature” of the system to have such symmetries.
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?
Finally, on page 183 of Scholastic Metaphysics, Feser expresses skepticism regarding the notion that there could be fundamental particles that are incapable of substantial change. 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?