ABSTRACT
Kant’s great contribution to metaphysics is the Critique of Pure Reason. In this chapter I focus on the central question of that great book: how is metaphysics possible? I distinguish between a few respects (epistemic, scientific, and metaphysical) in which, Kant argues, the possibility of metaphysics is questionable, and I focus on one of these: how is metaphysics semantically possible? I understand this question to mean: why do our basic metaphysical concepts (what Kant calls ‘categories’) refer (in Kant’s terms, have ‘objective validity’)? I first explain how Kant discovered this question by translating into the distinctive terms of his own cognitive semantics a question that Hume raised about causation, and then generalizing it to all ‘a priori’ concepts. I then explain Kant’s reasons for claiming that his predecessors (e.g., Locke, Leibniz, Wolff) failed to explain adequately why metaphysical concepts refer. I then turn to contemporary philosophy and argue that it is far from clear that contemporary metaphysicians have done a better job of explaining the reference of their concepts than Kant’s predecessors did. Potentially, Kant’s great question in metaphysics—‘Why do the categories have objective validity?’—is a question just as pressing today as it was in 1781.
