258 Kant: A Biographythe smell of an open sewer by sight that I cannot determine its smell in any
other way. Thus Kant thinks he can make a plausible case that the causal
connections have "their origin in pure understanding." Thus he argues that
(12) It is possible to introduce the concept of a priori connections by deducing
them from the pure understanding.
One can make a distinction between "local skepticism," or a skepticism
that relates only to a certain class of propositions, and "universal skepti¬
cism," or a skepticism that involves the doubting of the justifiability of any
knowledge claim. Kant believes that Hume essentially establishes a form
of "local skepticism," with "universal skepticism" being a hasty conclusion
founded upon the former. Moreover, Kant does not see Hume as denying
the existence of necessary synthetic judgments, but only as denying a
certain way of justifying them. So Kant thought that he needed to give only
a limited answer to Hume. All he had to do was justify synthetic a priori
judgments, whose existence was admitted by Hume.
Kant's Prolegomena approaches the problem of the Critique from this
perspective. First, there is the relatively short Introduction, in which
Hume gets so much attention. Assuring his readers that to do metaphysics
is as natural as breathing, that it "can never cease to be in demand — since
the interests of common sense are so intimately interwoven with it," he
argues that it needs reform precisely because of Hume's successful critique
of causality.^39 Secondly, he characterizes the peculiarities of all metaphysi¬
cal knowledge, which, of course have to do with the synthetic a priori nature
of its subject matter. Finally, he summarizes the contents of the first Cri¬
tique, using a new organizing principle. He asks four questions: (1) "How
Is Pure Mathematics Possible?", (2) "How Is a Pure Science of Nature Pos¬
sible?", (3) "How Is Metaphysics in General Possible?", and (4) "How Is
Metaphysics Possible as a Science?"
Kant finds the answer to the first question in the subject matter of the
Transcendental Aesthetic. Pure mathematics and its synthetic a priori cog¬
nitions are possible because space and time are a priori forms of intuition.
The answer to the second question can be found in the first part of the
Transcendental Logic. Science and its a priori cognitions are possible
because we have the categories and the principles. "The understanding
does not derive its laws (a priori) from, but prescribes them to, nature."^40
The third question deals with the subject matter of the Transcendental
Dialectic or with the ideas of pure reason as they concern psychology, cos¬
mology, and theology. These ideas arise naturally when we employ the cat-