No, that's not quite correct. Descartes called perception into doubt with the dream argument, and found that was not sufficient, since lots of propositions remained true. Blue is still blue, for example, even if no instances of blue in sense experience can be relied upon to indicate the existence of something blue outside the mind of the perceiver. Similarly, the square root of 16 is still 4, whether or not perception is reliable.
You seem to be confusing basic notions with clear and distinct ideas. As examples of basic notions, Descartes gives: knowing what doubt is and knowing what thinking is. IIRC, he took a basic notion to be such that any single such notion makes no metaphysical claims and is insufficient to support a metaphysical claim. His answer to EG doubt is to combine a few such notions to show that, together, they do support a substantive metaphysical claim.
You'll have to forgive me, I'm a touch rusty. Its been a long time since I've discussed this with anyone and some of the finer details have gone a little fuzzy on me. You're 100% correct that I'm confusing Basic Notions with Clear and Distinct Ideas. I seem to recall the latter being Descartes solution to the EG, but I'm willing to take your word for it since you seem more familiar with the entirety of the work than I am, and since it doesn't really change anything with regards to my position.
Well, sure, though have you read some of the recent stuff by Richard Gale and Alexander Pruss on their modal cosmological argument? The basic upshot is that, once you've shown that, given certain facts about the universe, there must be an unmoved mover, the gap problem (as it is usually called) maybe isn't quite as big as it first appeared. Of candidate ideas about what an unmoved mover could be, concepts like the theistic God are definitely in the neighborhood. And so for the other definitions (G and P's reasoning is more complex and about a different version of the CA). The point is that Aquinas may have had some such thoughts hanging around, but, lacking modern developments in formal modal logic, lacked the tools to properly express them.
I took a few minutes to read a little on this. Interesting stuff, but I didn't see anything (in my admittedly brief perusal) that made the gap problem any less severe. It boils down to the same problem, if one can prove that there are in fact Necessary Beings through abstract logic, how does one prove anything about the nature of said beings? All you can prove is that there must be
something that started the chain on contingent beings.
OK, so a couple of things just to be clear:
1. Now you're talking about teleological arguments, though you seem to be saying that in all five of Aquinas' arguments, there is an analogous move from what should be inferred from the argument to God. While I don't quite agree, I suppose it's clear enough that we can proceed.
2. The "premise that follows" isn't a premise, but a conclusion, though I would agree it's not a well-supported one.
Do you mean that it is possible for a proposition expressing EG doubt to be true while Aquinas' definitions of God are also true? It still isn't clear how this is a threat to any of Aquinas' arguments.
I did jump to a different argument, it just seemed a better example, and any of the 5 ways fall into the same trap, imo.
To put it simply, using the argument from design.
1. A watch can not come from nature
2. Watches exist
3. A watchmaker therefore
must exist, because a watch can not exist without a watchmaker
4. Like the watch, life is too complex to arise from nature
5. A designer of life
must therefore exist.
6. This designer is God.
#6 is a declaration that sits independent of the argument and does not follow from the premises. #5 is really the conclusion, and leaves you with an undefined necessary being. #6 could just as easily be "This designer is the EG", and the entire package would be just as plausible. Therefore, god does not exist by necessity, since the EG could just as easily be the designer of life. Arguments from necessity like this always attempt to prove the existence of
something, and sometimes succeed. But never do they prove the existence of god, only The Uncaused Cause, Designer of life, etc. I suppose this all falls under the gap problem, and the EG is just one way of pointing out that if one wishes to prove gods existence using an argument from necessity, one must find a way of addressing the gap problem, because it will always arise if the person listening to you isn't just looking for something to hang their faith on.
Unless one is not out to prove god exists, and is happy applying the label of God to whatever necessary being lies at the end of their argument. I suppose this is possible. I wouldn't want to pray to the EG though lol.