Abstract

At his point of entry into practical philosophy, Kant remarked that just as theoretical philosophy must be grounded in a critical investigation of theoretical reason, practical philosophy must be grounded in a critical investigation of practical reason. He added, however, that the latter investigation must also exhibit practical reason’s “unity” with theoretical “in a common principle,” because “in the end there can be only one and the same reason, which must be distinguished merely in the application” (G, 4: 391). Soon thereafter Kant published his critical investigation of practical reason, and in that work he drew comparisons between theoretical and practical reason and considered their relation to one another. […] But this problem presupposes the identity of reason. Only under the supposition that one and the same reason is at work in two applications could an apparent conflict between theoretical and practical reason pose a threat to unity. So before pressing forward to questions relating to unity, it may serve us well to ensure that we sufficiently comprehend reason’s identity. Kant’s fruitful insight that consciousness of the identity of the I think can yield recognition of the unity of the understanding encourages the anticipation that reflection on reason’s identity may similarly illuminate the unity of reason.