Jeremy Taylor wrote:

I think Lloyd Gerson, in his Plotinus, succinctly states why some notion of potency seems essential:

​Surely, though, the Stoics could reject the legitimacy of the concept of potency all together. But this entails a rejection of a real distinction between potency and actuality. Then, in referring to the present in relation to the future, there is no way to distinguish non-arbitrarily what something has the potency for being what something does not have the potency for being. Every moment should be a total surprise, because nothing that was a moment ago has any relevance to what is going to be.

​Physics and metaphysis are distinct levels of analysis. The physicist qua physicist doesn't worry about things like basic accounts of causation. He assumes them. That the physicist has no interest or knowledge of the distinction between act and potency means little.
 

Its a bit more complicated than that Jeremy. For example on the issue of change, the whole point was that you could not have something coming out of nothing and so Aristotle came up with potentiality. A physicist would simply say that quantum mechanics dictate how matter interacts and thus what you see is just the working of qunatum mechanics. It's just how this matter behaves if certain conditions are provided. In a simple case a physicist would say that matter exists, there is no experiment showing matter going out of existence, so why should one give an account why matter exists? Of course, I agree that there should be a starting point,(there should be self-sufficient thing). However, a physicist would simply say that matter is self-sufficient. It maybe the atom or quarks or what have you, we might not even be able to know that there is actually something smaller than quarks but a physicist would say then that thing is the self-sufficient being and thus all we see is just the interaction of these smallest beings. 
 

I think I have enough knowledge to more or less have a feeling for Aquinas' metaphysics and I can assuredly say that I have a very good grasp of physics due to my university education. The point is that the picture that classical physics draw is so radically different than Thomistic metaphysics.I cannot believe that anyone with an understanding of classical physics would not face serious problems with Thomistic metaphysics. On othe other hand, the people here who have studied Aquinas' metaphysics seem to have no or little grasp of classical physics. So you have this constant clash because none of the sides really understand the framework of each others' point of view. I think its better for physicsts to go do academic philosophy or philosopher to go and do academic physics but no ordinary people who seem to have at most a background in one area,

 

Miguel wrote:

nojoum wrote:

Thank you very much for taking the time and making the effort to write such comprehensive explanation.
I hope I am not guity of being dismissive, but to me it seems that you are basically saying why should something remain in existence.
If this is the case, then I think the first way is wholly irrelvant to the discussion.

I think a materialist can just resort to brute fact and says that the universe as a whole essentially exists (its pure act in the sense of existence)

 
The argument I made is based on conditioned existence, so it is not the first way, strictly speaking. But as I explained, motion can figure into the argument, because "act" and "potency" can be used to investigate the idea of existence and essence; the first way is "neutral" in a sense, motion can be applied to existence, the relation of parts and oneness, the idea of form and matter, etc.

"I think a materialist can just resort to brute fact"

Of course a materialist can do that. But that would require a rejection of PSR, and part of the argument involves establishing PSR. Therefore it would beg the question unless the atheist can defuse my arguments and also show how it would be acceptable to settle for a brute fact here. I have yet to see how anyone can even do that.

"The universe as a whole essentially exists (its pure act in the sense of existence)"

That would grant that there is a self-sufficient being. The problem is that identifying it with the universe is absurd, and I've argued why we cannot hold that any material being is self-sufficient, see some of my other posts discussing this here. The atheist would have to defuse these arguments. Moreover, he cannot say that even though the parts of the universe (individual material beings) are conditioned existents but the universe as a whole is not, because the system depends on its parts, is made up of them, and is therefore not self-sufficient -- and that is even if a "higher mode of being" emerges from th

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