The Ideal of Pure Reason is concerned with the arguments of rational theology. As with the paralogisms and the antinomies, Kant's ultimate aim in the Ideal is twofold. On the one hand, he argues that the idea of God is necessary and inevitable. On the other hand, he tries to show how any attempt on the part of speculative reason to determine this idea a priori (i. e., to acquire knowledge about the existence or attributes of God) is dialectical. In sections 2 and 3 of the Ideal, Kant attempts to account for the rational origin of the idea of God; in sections 4–6, he argues against the three species of argument for the existence of God: the ontological, cosmological, and physicotheological. But because Kant contends that the ontological argument is presupposed by the other two, and because a considerable part of Kant's critique is aimed at showing this, we limit our attention here to the criticism of this argument. After some preliminary remarks, the chapter considers Kant's account, in section 2 of the Ideal, of the origin and subreption of the idea of the ens realissimum; examines what I take to be Kant's effort to show that the metaphysicians' tendency to hypostatize and personify the above ideal of reason issues from the transcendental and illusory principle P2, and its demand for an unconditionally necessary being; and examines Kant's criticism of the ontological argument.