"All-Crushing" Critic of Metaphysics 243view the world as spatial and temporal, things in space and time, or "the
appearances," are objective for us. Kant says that they are "empirically real"
but "transcendentally ideal." If we were constituted differently, we might
be able to "see" (or intuit) things as they are in themselves and not just as
they appear to us. As finite beings, we cannot experience anything without
our senses. Space and time are necessary conditions of any experience for
us. As such, they provide us with a priori knowledge of the world of our
experience. We can know that the world of experience must have certain
spatial and temporal characteristics. Geometry and arithmetic are the sci¬
ences dealing with synthetic a priori judgments that are based on space
and time. Most of what Kant has to say in the Transcendental Aesthetic,
that is, the section dealing with the a priori forms of sensibility, can already
be found in the Inaugural Dissertation.
Second, our knowledge is dependent on the forms of the understand¬
ing, or on a number of basic a priori concepts. Kant discusses these a priori
concepts in the first part of the Transcendental Logic, also called the An¬
alytic of Concepts. Borrowing a term from Aristotle, he calls these basic
concepts categories. Though similar to his view in the dissertation of 1770,
his view here differs in some respects. For one thing, in the earlier work he
had given an open-ended list. In the Critique, he claims that there must be
exactly twelve such categories, and he is sure that he has derived them
with a strict proof from a single principle. The categories now consist of
the basic concepts of quantity (unity, plurality, and totality), quality (re¬
ality, negation, and limitation), relation (inherence, causality, and commu¬
nity), and modality (possibility/impossibility, existence/nonexistence, and
necessity/contingency). They can accordingly be arranged in a table con¬
sisting of four groups, each containing three categories. Kant tries to de¬
rive them in a chapter entitled "The Transcendental Clue to the Discovery
of All Pure Concepts of the Understanding," usually called the Metaphys¬
ical Deduction.
The categories appear to have a wider application than the concepts of
space and time because we seem to be able to make claims about things
that are not part of our spatio-temporal world. Many philosophers use the
concept of causality, for instance, in talking about God and in devising
proofs for his existence, but they also claim that God is neither in space
nor in time. Kant, like Hume before him, is convinced that this is a mis¬
take. Yet he rejects Hume's contention that the concept of cause must be
restricted to experience because it has been derived from experience; the
categories are a priori concepts and therefore independent of experience.