On Chastek's interpretation of Aquinas' Fourth Way

Focusing on this blog post.

The argument here is based on Aquinas' versions of two kinds of explanation -- perse and primo. They are explained in the following passage.

Chastek wrote:

Aristotle distinguished two senses of perseity. In the first, any intrinsic connection between a subject and predicate will be a per se connection. In this sense, when we say an exothermic reaction is hot we say something per se, since it falls in the very definition of exothermic reaction that they give off heat. There is, however, a stricter sense in which it is not precisely the exothermic reaction that is hot, but only the mean molecular motion, since it is only this latter that is precisely what heat is, and it is in virtue of exothermic reactions giving rise to such motion that they are hot. Aristotle called the looser sense of the per se kath’ auto, which can be unproblematically translated as  “per se”, but he called the stricter sense katholou (or “universal” in the genitive case) which we will here call primo since this was the Medieval usage. It is this strict sense of the per se – the per se and primo – that we target when we seek to explain something, even if, for practical reasons, we are often content with explanations that fall short of this level of rigor.

The example is kind of a mess.
Per se example: an exothermic reaction is hot.
Primo example: mean molecular motion is hot.

I'll take 'per se' and 'primo' to be predicates that apply to claims or explanations (following Chastek).
It seems like a claim 'X is Y' is per se iff X is intrinsically Y. (There are lots of theories of intrinsicness, but I'll assume Chastek is neutral on this.)
It seems like a claim 'X is Y' is primo iff X is essentially Y. (Chastek doesn't use the term 'essential', but this seems to be what he's getting at with the statistical mechanics example.)

Note that 'intrinsic' and 'essential' are distinct. (Here's a paper on the relation between them.)

One problem with the passage is that the 'is' in the first claim (an exothermic reaction is hot) is a copula -- it predicates hotness of the reaction. However, the 'is' in the second claim (mean molecular motion is hot) isn't even true. If the mean of the molecular motion is low, then it won't be hot at all. What Chastek means here is 'mean molecular motion is heat'. And the 'is' in this claim is an identity, not a copula.

Now for the argument.

Chastek wrote:

The Fourth Way starts from no specific class of facts, but from any fact about the world which, when understood per se and primo, deserves to be called God. St. Thomas need not be seen as restricting himself only to “transcendental perfections”, as the manual Thomists have read him. The Fourth Way can, in fact, start with things given in all the other four proofs, and can reach all the conclusions they reach by its own proper way of proceeding and without appeal to any extra premises. For example, we see movers that are more and less immobile, and so there must be some mover that is immobile per se and first; we see causes that are more and less causal, so some cause must be per se and first; and we see necessary things that are more and less necessary, and thus there is something whose necessity is per se and first. If such a being is “what all call God” in the preceeding proofs, it is also in this case.

So Chastek rejects the "transcendentals" reading, which is great. However, I don't see the example argument given to be one that is at all plausible.

Chastek:
Things are more or less immobile.
So there must be a mover that is immobile per se and primo.

Here we have what I've called the "more / most" inference. It has the form:
Xs can be more or less Y.
Therefore some X is maximally Y

But notice how far off the rails the discussion has gone. Motion isn't intrinsic or essential. So this example is hopelessly confused. Moreover, why think that an intrinsic property or an essential property would have to be maximal? That makes no sense at all.

Moreover, Chastek seems to think that this argument can be applied widely. Let's see another example:

Things are more or less long
So, there must be a thing that is long per se and primo.

Two problems: the inference is invalid -- the premise is true and the conclusion is false. Moreover, even if the conclusion were true, there is no reason to think that admitting of degrees (being more or less) has anything at all to do with intrinsic or essential properties. Finally, even if we granted that something is essentially long, there is no reason to think that that thing would be maximally long.

Overall, I applaud Chastek's attempt to get away from the "transcendentals" reading, but I don't see any hope for the "perseity" reading.

Jason wrote:

Firstly, I would like to say that I myself do not fully understand the fourth way. It is probably the hardest argument in all the five ways to fully understand and we should probably start from at least discussing the other four ways. Even Chastek says 

"Chastek" wrote:

The Fourth Way can, in fact, start with things given in all the other four proofs, and can reach all the conclusions they reach by its own proper way of proceeding and without appeal to any extra premises.

Secondly, with repeated calls from all of us here to read the background metaphysics I do not understand why you say the following

"KevinScharp" wrote:

But notice how far off the rails the discussion has gone. Motion isn't intrinsic or essential. So this example is hopelessly confused. Moreover, why think that an intrinsic property or an essential property would have to be maximal? That makes no sense at all.

The word motion (Aristotelian) is not motion as the moderns think but change as in the actualization of a potential. If that is not intrinsic or essential then I am not sure what is. Now if you see the example Chastek gave with the context of what motion means can you see why there must be a “mover”?

I've read the background metaphysics. However, what you're saying has nothing to do with metaphysics, it has to do with the meaning of a word. If you like, we can assume that the ancient Greeks meant change by the word that gets translated into English as 'motion'. You're wrong about this, but it doesn't matter. Would it be true that any change requires a changer? That's the way you would have to interpret "any motion requires a mover" based on your assumption about the meaning of 'motion'. Does any change require a changer? No. This principle is far more obviously false than the other one (any motion requires a mover).

Moreover, the funny thing is that "motion requires a mover" has nothing to do with my criticism of Chastek's interpretation of the fourth way.

Finally, motion (as we use the word) is a kind of change. So if my criticism (i.e., that motion isn't even intrinsic much less essential) was a good one based on my understanding of the word 'motion', then it would still be good on your understanding of it.

So I don't see how a better understanding of the background metaphysics would help here. Can you explain?
 

Alright, unfortunately I have to focus all my time on moving my family to a new city. I have not only enjoyed participating in this great conversation with you all, but I feel like I've benefited tremendously.  I'm interested in getting my opponents' views right when thinking critically about them. I can't tell you how helpful it is to me to see the kinds of views and reasons you all propose. So thank you.

I would love to start this back up in a couple of weeks because I have several conversations open right now (especially Jason and Alexander) that I'd love to pursue and I have several other topics I'd love to discuss. Do you all have a preference for whether I should pick up this thread (which has become rather popular) or start a new thread? 

Thank you for taking time out of your busy schedule to discuss these important issues here with us, appreciate it. In terms of posting in this or any other thread I think it would be totally upto you how you feel comfortable. Looking forward to some excellent discussions. Wishing you and your family the very best on the move.