The book is definitely hard going, and Kant is not easy to understand, so I probably will have trouble summarizing it clearly, and will have to rely on vague language as a sort of smokescreen.
One of Aquinas's arguments or proofs for the existence of God is that of the "First Cause".
Motion, i.e. the passing from power to act, as it takes place in the universe implies a first unmoved Mover (primum movens immobile), who is God; else we should postulate an infinite series of movers, which is inconceivable.Hume opposed both the idea of "cause" in itself .... that one thing was actually "caused" by another, or at least, that our minds could know them to be.
For the same reason efficient causes, as we see them operating in this world, imply the existence of a First Cause that is uncaused, i.e. that possesses in itself the sufficient reason for its existence; and this is God.
From what I understand, Kant thought that all our thinking was either "a posteriori" (conclusions drawn from empirical experience) or "a priori" (intuitions that made thinking about empirical experience possible in the first place). So he thought that notions of time and space were "a priori". They weren't gained by experience per se, but were the mental pre-conditions that made it possible to make mental order of experience to start with.
So he did not think there was any way our minds could come to the notion of a First Cause, because a first cause by definition is outside of "a posteriori" experience and so it is over-applying particulars and in particular, extending a "category" out to where it couldn't apply.
The way I understand it, if you assume that every result has a cause, you have two choices:
- An infinite retrograde of causes.
- Some First Cause that put everything else in motion.
But thinkers like Hume wouldn't propose that every effect has a cause, even, or at least, that our minds are able to propose that with any kind of certainty. I don't understand that one very well yet. Certainly it is a difficult mental stretch to think that way.
Kant thought of "cause" as a way of thinking rather than a reflection of reality per se and in that way, he thought that our minds simply could not come to a knowledge of these things outside the sphere of a posteriori knowledge (knowledge derived from experience). This didn't rule out the existence of God for him, by the way -- he had proofs of his own, which are sort of weak.
Anyway, from childhood without knowing anything about Aquinas I'd always just assumed that given that reality DID exist, that there couldn't be an infinite retrograde of causes or motions. Something had to have started it all. I guess that wasn't a given though to the Enlightenment and post-Enlightenment fallacies. It was easy for me to jump from the reality of my consciousness to some kind of originator of my existence. Kant thought that this skipped several steps. But all the same, it isn't a ridiculous assumption, given that the alternative leads to lots of problems. The possibility of infinite retrograde seems to confuse physics with metaphysics in a way that a First Cause does not.
Jacques Maritain, a post-Kantian Thomist scholar, thought that Kant's thinking was a form of nominalism. He held that "the critique of knowledge is part of metaphysics" which puts into words something that has bugged me about Kant's reasoning. But now I am really getting over my head.
Also, in Traditional Logic Martin Cothran says that Descartes "Cogito ergo sum" is a formal fallacy. I don't remember exactly why that would be, and it is too cold in the house to get out of my blanket and rummage around in my curriculum closet. Certainly it is an enthymeme lacking a minor premise. I would frame the syllogism this way, and certainly this was my own mental process as a teenager:
- I have consciousness.
- To have consciousness is to exist.
- Therefore, I exist.
It looks OK formally. Or am I wrong about that? Anyone?
(ETA that Martin Cothran didn't actually call "cogito ergo sum" a fallacy, and he points it out very kindly in a comment on this post; he actually did call it an enthymeme; and it's in Chapter 6 of TL 2 under enthymemes. Next time I will definitely drag myself to my bookshelf to check before I make a statement like that).
That clicking sound is my statcounter reader count dropping down next to zero, I am sure. Mental wrestling is a boring spectator sport. That reminds me of an idea my husband used to propose to amuse himself..... Game Programming Olympics. Two or more game designers would go head to head, duct-taped glasses perched on nose and plastic pocket protectors in place, fueled with vending machine Snickers and Big Gulps, and ... they would program. There could be a commentator, and a thrilling soundtrack.... like the Rocky theme song, Come and Fly Now or Thus Spake Zarusthusa. Everyone would turn on their TVs to watch. Yep!
There's a bit more about the Cosmological Argument, here. I used it a bit to help my rephrasing but any mistakes in accuracy are mine, not Stanford's, I'm sure.