This chapter examines three of Kant's most important arguments, those responding to skepticism. From the Greeks up to Hume, skeptics attacked metaphysical claims about reality, especially regarding substance, causal connections, and the external world. Kant replies to these attacks in the Analogies of Experience and the Postulates of Empirical Thought, where he defends pure principles based on the relational and modal categories. According to Kant's proofs, these regulative principles supply the elements required to turn mere intuitions into perceptions of objects in the “weighty” sense, as subject-independent entities in unified space and time. The Analogies argue that the principles of substance and causal connection are necessary to locate events in objective time. The Postulates of Empirical Thought, which include the Refutation of Idealism, demonstrate the principles enabling subjects to judge the real possibility, actuality, and necessity of states of affairs. Here I first explain Kant's arguments for these principles, and then comment on Kant's success in answering skepticism.

THE ANALOGIES OF EXPERIENCE

The Analogies argue that the a priori concepts of substance and causality are required to order appearances in one time. Although the text contains a distinct proof for each category, the introduction argues for a general principle emphasizing the notion of objective time-determination. The A edition principle states: “As regards their existence, all appearances stand a priori under rules of the determination of their relation to each other in one time” (A176/B218).