This chapter turns to the philosophical revolution of Kant. Starting from what he described as his ‘Copernican’ revolution in epistemology, it examines what he took to be its implications, negative and positive, for metaphysics, ethics, and religion. It examines Kant’s account of freedom as autonomy; his moral theory and its basis in the categorical imperative; his conception of the relation between morality and practical reason; and his ethical views and ideals. His political views are examined in relation to the ideas identified in Chapter I, particularly those of the revolutionary thinker Sieyès. In the concluding section Kant’s critical and hermeneutic stance in metaphysics and ethics is defended. It is argued, however, that while transcendental idealism is a powerful response to the problem of knowledge, it is not required for a full account of freedom, will, and reason.