Immanuel Kant (1724-1804)

1. Immanuel Kant (1724-1804) Prolegomena to Any Future Metaphysics

2. Is Metaphysics Possible? • Metaphysics requires knowledge that is apodictic (necessary). • Only a priori knowledge is necessary. • Hume has shown that there cannot be any a priori knowledge. • Therefore, metaphysics is impossible.

3. A priori judgments • A priori refers to the way a claim is known. • It is an epistemological concept. • If a claim is known a priori, then it is known through reason alone and it is necessary.

4. A posteriori judgments • A posteriori refers to the way a claim is known. • It is an epistemological concept. • If a claim is known a posteriori, then it is known through experience and it is contingent.

5. Analytic judgments • Provide no new knowledge. • “Explicative” • Their predicate is already included in the notion or concept of the subject. • Their truth is based on the law of contradiction.

6. Analytic judgments • “All bodies are extended.” • This is an analytical claim because being extended is part of the definition of a body. • “All bachelors are unmarried men” is also an analytic proposition.

7. Synthetic judgments • Provide new knowledge. • “Expansive” • The predicate is not already included in the notion or concept of the subject. • Their opposite is not a contradiction.

8. Hume

9. Synthetic a priori judgments? • How are synthetic a priori claims possible? • Where does the necessity come from? • It cannot be based on the law of contradiction. • See p. 24 for a description of the difficulty.

10. Mathematical judgments • Kant argues that mathematical judgments are synthetic. • 5+7=12 is a synthetic judgment. • The sum of 5 and 7 is a different idea than the idea of 12. Something else is required to derive the idea of 12, some intuition.

11. Kant • “There remain therefore only synthetical propositions a priori of which the possibility must be sought or investigated, because they must depend upon other principles than the law of contradiction” (22-23). • We shall start from the fact that such synthetical but purely rational knowledge actually exist” (23).

12. Transcendental Philosophy • It is not metaphysics per se, but rather the investigation of how metaphysics is possible. • “It might be said that the entire transcendental philosophy, which necessarily precedes all metaphysics, is nothing but the complete solution of the problem here propounded, in systematic order and completeness, and hence we have hitherto never has any transcendental philosophy” (26).

13. Transcendental Problem 1) How is pure mathematics possible? 2) How is pure natural science? 3) How is metaphysics in general possible? 4) How is metaphysics as a science possible?