I think at this point I understand all the transcendental arguments of CPR except this one - and probably this could considerably change my understanding of Kant as a whole.

Here is my confusion.

  1. Intuitions are a priori.
  2. Concepts are a priori.
  3. This might be a bit contestable but Kant in various locations does state pure appearances exist (intuitions without concepts). But they serve no value for us since it makes no judgement. There cannot be a true/false value attached to it, since it's not a judgement.
  4. However, we DO apply concepts without intuitions. This is the mistaken field of metaphysics as explicated in Transcendental Dialectic.

Now, if 1 and 2 are true, and Kant can grant 3 (however, this is not crucial to my argument), with what exact reasoning can he state that 4 is 'empty'. I can understand if he says they are 'useless'. But in the transcendental dialectic, his position is more than these metaphysical statements being useless - it is that they are incorrect/erroneous. His position is that it is a mistake to use concepts without intuitions.

For this, in my opinion, he will need to elucidate that concepts CANNOT exist without intuitions, i.e, their content is derived from intuitions. However, it cannot be 'derived' by definition, since they are a priori. On top of that we know they do exist independently in the field of metaphysics - Kant himself claims this.

So while, as a Nietzchean perhaps, I can grant Kant that concepts applied to things that cannot be present in intuition is probably useless (this is an ethical argument, not an epistemological one), I still cannot grant Kant an ontological reason for why I should not use concepts without intuitions in my discussions (which is what metaphysics did before him).

And yes, this argument is a part of Transcendental Deduction, but it's (a) quite unclear and (b) not satisfactory in my opinion because just because categories are a presupposition of experience which also involve intuition in no way mean applying them without intuitions is illegitimate.


I realized this question can be posed in a different way. (This is partly due to the fact the answer might just resort to the fact that synthetic a priori judgements require predicates that we can only get through intuitions).

  1. Are metaphysical judgements synthetic a priori? If not, how are they possible. They are not analytical, of course.
  2. If they are synthetic a priori, how can they be mistaken, given that they are a priori and the entire system of Kant depends universalizing that which is a priori.
  • Empty concepts for Kant are epistemically useless, so it is about epistemology, not ethics. And concepts can not be "erroneous", only what is done with them can be. Kant's contention is that what is done in metaphysics is exactly that, a "transcendental illusion". Rainbow by itself is not "erroneous", it is taking it for a corporeal body, mis-taking it, that is. It is not "erroneous" to play imaginary games with noumena, as long as one is not falling into contradictions. It is metaphysical mis-taking them for something other than empty speculations that is the illusion. – Conifold Jun 16 at 6:35
  • I do not quite understand the boundary for "imaginary", if everything can be a priori - intuition and concept both. Sounds like a triangle could also be imaginary and mathematics is not epistemically useless - now this is because Kant claims it is a synthetic a priori judgement. What makes metaphysics NOT synthetic a priori? And, if it is synthetic a priori, then why is it useless? – Rajan Aggarwal Jun 16 at 13:53
  • Mathematics is equally useless if it operates like metaphysics, as he explains with the angle sum theorem. There is no deriving it by inspecting the concept of triangle. Instead it constructs its objects in productive imagination using forms of intuition, the same forms that are used in transcendental schematism to differentiate sensations into perceptions and subsume them under concepts. Hence the result is applicable to appearances while remaining a priori. To do the same in metaphysics we'd need "intellectual intuition" that constructs real things, not just forms. But... we are not God. – Conifold Jun 17 at 5:31

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