As I continue my deep read of Kant's first critique, I'm struck by the fact that both space and time are a priori concepts, known to us prior to any experience, CPR(A) Transcendental Aesthetic, S.7 p.39-40. But so too are the 12 categories in his framework. To be pure concepts, he tells us, they must also be a priori. CPR(A), Transcendental Logic, S.10, p.78-79.

What is the operative relationship among Kant's a priori elements?

A skeptic may ask whether is matters. But it matters in my analysis because I am trying to understand whether the nature of the 12 categories are essentially equivalent to space and time, or somehow derived from them.

In his first critique, space and time are "two totally distinct kinds of concepts" and specificially describes them as "forms of sensibility", whereas, in the same paragraph the categories themselves are "concepts of the understanding" CPR(A) S.13, p.85-86. This takes me down the path of separateness. And yet, as a priori concepts, there is a sameness that to me makes them function in a similar way, generalized abstractions with which we can categorize and frame our knowledge.

What guidance is available on this?


Kant goes through our three faculties of knowledge (Sensuousness, Understanding, Reason) in the Transcendental Aesthetics, Analytics and Dialectics. In every faculty he is searching for perceptions a priori and their relation to objects.

So space and time are a priori knowledge from our Sensuousness (its form !), the categories from our Understanding. The transcendental ideas are the perceptions a priori from Reason, but they are problematic because of their lack of an object in experience, although able to be thought without contradiction (definition A254|B310). Space, time and the categories have objects in experience (i.e. every sensual intuition) and are therefore knowledge.

A priori concepts they are in the same sense as they are necessary conditions of our relationality to objects (question from his letter to Herz from 1773). They are not thought "before" any experience in a sense of time, but in a sense of inference.

Regarding the relation between space and time on the one hand and the categories on the other hand there is another aspect already established in his dissertation and repeated in the Transcendental Deduction: Time and space as forms of intuition are used for the conclusion that sensual intuitions are mere appearances.
What is new in CPR is that Categories as the most abstract concepts of our relation to sensual objects (which for us is only possible in form of intuitions!) can only be applied to intuitions, therefore are underlying the form of space and time, too.

I suggest reading Eckart Förster's The 25 Years of Philosophy for a quite good presentation of the overarching argument.

  • Helpful @PhilipKlocking .. especially the thought of space/time and the categories sequenced not in time, but to enable inference. Establishing conditions ..
    – sourcepov
    Dec 15 '15 at 1:34

Space and time, for Kant, are essentially different but interdependent; they're essentially different from the categories - if the word essential is to retain its meaning.

The categories derive from Aristotles as a way of categorising the things that are; they're part of his onto-logic.

Kant reconceptualises them within his critical philosophy so that science, that is objective knowledge is possible; because science deals with things that are; this is his answer to Humes critique of induction.

I'm not sure that they need to be known to us in some specific order; but certainly Kant introduces them in a certain order because he's building up a system step-by-step; I expect he uses the forms of space and time in transcendental deduction that justifies his conceptualisation of the categories.

  • .. yes, conditions that help Kant build the case. The essence of each pure concept is different, but connected as part of the framework. An ontology of abstraction perhaps? It may be interesting to circle back to Aristotle's 10-15 predicables, as I believe Kant describes them, just to survey the raw material. I'm still learning how the categories operate. I understand the break down of his 4 class groupings, I think .. but not yet the relationships .. the verbs betwixt them.
    – sourcepov
    Dec 15 '15 at 1:46

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