3.2 God in the Critique of Pure Reason's Transcendental Dialectic
3.2.1 The Ens Realissimum

The Transcendental Dialectic's “Ideal of Reason” contains the best known and most frequently anthologized components of Kant's philosophy of religion. In addition to its portrayal of the ens realissimum, one finds within it Kant's objections to the Ontological, Cosmological and Physico-theological (Design) arguments for God's existence. It is thus the text most central to the negative elements of Kant's philosophy of religion and is integral to the widely held view that Kant is deeply hostile to faith.

The general aim of the Transcendental Dialectic is to expose reason's excesses, its drive to move beyond the limits of possible experience, and to bring all concepts into a systematic unity under an “unconditioned condition.” The Transcendental Dialectic begins with a critique of reason's illusions and errors within the sphere of Rational Psychology. It then moves on to a critique of cosmological metaphysics, and then to the “Ideal of Reason” where Kant turns to Rational Theology and its pursuit of religious knowledge.

As Kant explains, underlying all the traditional proofs for God's existence is the concept of the ens realissimum, the most real being. Reason comes to the idea of this being through the principle that every individuated object is subject to the “principle of complete determination.” While the generality of concepts allow them to be less than fully determined (e.g. our concept of a horse extends over horses that are different colors, heights, etc.), individuated objects must be completely determined (e.g. an individual horse must have specific colors, a specific height, etc.).

Hence, where the particular determinations of actual objects are discovered through experience, our concepts, which in themselves are not objects of experience, necessarily