In his critical period, Kant thought that scepticism was a threat to the metaphysical enterprise of Enlightenment. He consequently tried to tackle three of its species: Baylean scepticism, which doubts that reason could establish any truth concerning its ideas; Humean scepticism, which must be distinguished from Hume's formulation of the problem if we want to show that synthetica priorijudgements are possible; and Cartesian scepticism, which puts in doubt the reference of empirical concepts to things in the external world. Kant's treatment (...) reveals the fundamental role played by scepticism in his critical enterprise not only as a triple challenge to the critical project, but also as an ally against idealist dogmatism. (shrink)