 The first thing to note is Kant’s bold claim that reason is the arbiter of truth in all judgments—empirical as well as metaphysical. Unfortunately, he barely develops this thought, and the issue has attracted surprisingly little attention in the literature. (But cf. Walker 1989: Ch. 4; Guyer and Walker 1990;  Kant’s theory of judgment,  §§1.3,  1.4).[2]  However, some basic points are clear from the text. We form judgments about the world around us all the time, without a second thought. We see a hand in front of us and judge it to exist; after a dream, we judge ourselves to have been dreaming and the dream’s contents to be illusory; we see the sun rise and assume that it orbits the earth. Kant devotes great philosophical efforts to show that all these judgments rely on categories, such as cause and effect, that must order our sensory impressions. A belief that conforms to these conditions meets the “formal” conditions of truth. However, unless we are fundamentally confused about something, all our beliefs meet these  conditions.[3])  So there is a further question: which of our beliefs are “materially” true, and which erroneous?