Noumenon and The Thing in Itself

[peter]

Well Descartes is famous for his starting from the standpoint that nothing (re ..., well, anything really) can be taken for granted (is he not?): Did Kant assume the same in the more circumscribed area of human reason, or was he prepared to accept the work of those who had gone before, or did he also demand a 'tabula rasa' as the starting point of his critique?

[Mighara Sovmadhi]

Kant appears to have had a much better grasp of the history of science and philosophy than Descartes. OTOH Descartes contributed enormously to mathematics so IDK. As far as the Cartesian cogito goes, I'm pretty sure Augustine had come up with an almost identical thought along this line.

[Zarathustra]

Kant doesn't really start with a tabula rasa, since he's arguing for the categories of human thought/perception/experience that shape our judgments a priori. But in another sense, he does sort of wipe the slate (of the history of philosophy) clean by doing something unprecedented with his "Copernican revolution" in philosophy, where he assumes that objects conform to intuition rather than the other way around (see above: categories). And this all happened due to Hume waking Kant from his 'dogmatic slumbers,' by showing that there really is a problem on both sides of the rationalism/empiricism divide, where neither can give knowledge of the world, collapsing into either tautology or skepticism. So I don't believe Kant ever has a point where he doubts everything (honestly, neither does Descartes ... he just pretends to), he just recognizes the problematic nature of naive realism as well as the problems with all the sophisticated attempts of others to relieve it of its naivete.

So, to answer Peter's question, Kant was directly and consciously responding to the entire history of philosophy that went before him, a history had which culminated in a stalemate between the two major schools of Western thought, rationalism vs empiricism. Descarte was just sort of talking out of his ass, "armchair" philosophy. That's not to say it wasn't important or intelligent, but that it was much less scholarly. Kant envisioned himself as bridging the divide between these two schools of thought, solving their problems (which, in my opinion, didn't really happen until Husserl).

[Mighara Sovmadhi]

In line with Z's commentary:

Let's say, "I think, therefore I exist," is the Cartesian axiom. Really, it's an enthymeme(sp.?) for a whole argument, to wit something like:

• 1. I think [or I doubt].
  2. Thinking is an action.
  3. Action implies an actor/one who acts.
  C. Therefore, my thinking implies me [existing].

Kant, on the other hand, has for an axiom something called the principle of the transcendental unity of apperception: "All specific examples of my thoughts [propositions] are predicable of the 'I think' proposition [as in "I think that 2*2=4, that red is a color, etc.]." Now the "I think" contains the types of propositions, e.g. if-then claims, this-or-that claims, necessarily-or-contingently claims, etc. and so the same "I think" that in pure abstraction gives us the logical unity of our propositional attitudes, gives us the transcendental unity of our empirical perceptions. So what in pure logic's adjudication of thought is the if-then relation, is the relation of cause-to-effect in objects of sensation.

Of course Kant can accept that the "I think" is the cogito also, but the route he goes to vying with the external-world skeptic doesn't default on trying to find an innate concept of a trustworthy creator but something like, "Unless we know some external fact first, we would never form the idea of an external fact at all; but if we know an external fact, we have the criterion of externality," which has to do with the nature of temporal awareness relative to the concept of material particles/substance/etc.