Critique of Pure Reason

“The Deduction of the Pure Concepts of Understanding” is some of the most mind-bending material in modern philosophy. Kant was aware of his reader’s potential confusion: “Such obscurity is unavoidable as one begins to walk along a path that has never been walked upon before” (153). Kant’s task in this book is to determine the limits of experience. Among other things, this entails comprehension of how conscious experience is possible at all. Thus far, Kant has already identified sensibility and understanding as the two faculties of the human mind necessary for experience and has outlined the basic nature of both. Now he must show how they can be combined to present a unified world of appearances.

To do this, this he must introduce the idea of the imagination, which brings the world of intuition in sensibility to an image presented before consciousness, and, more fundamentally, the transcendental unity of apperception. The latter is the idea of a self, a conscious I, that accompanies and unifies all experience. Without this act of unification there is nothing to bind experiences together. Kant writes, “Hence the original and necessary consciousness of one’s own identity is at the same time a consciousness of an equally necessary unity of the synthesis of all appearances according to concepts” (159). In other words, self-consciousness is that which brings all subsequent acts of understanding, which acts through categorization and judgment, under one fully realized umbrella.

At the time, this was a novel idea. In the 17th-18th centuries there were serious debates regarding the nature of personal identity, including David Hume’s skeptical denial of the reality of personal identity. By making personal identity the defining condition for the possibility of experience, Kant overcomes the problems of identity articulated by Hume. Kant takes this as a ground of all cognition: “And thus the synthetic unity of apperception is the highest point, to which we must attach all use of the understanding, even the whole of logic, and in accordance with it transcendental philosophy” (178).

One of the intriguing elements of Kant’s transcendental idealism is the fact that his work is concerned primarily with the “subjective sources of cognition,” of which there are three: sense, imagination, and apperception. This does not mean that there are not also objective sources of cognition. This objective source is the transcendental object, i.e., the object as it is independent of our experience of it. However, since we cannot know anything about the object as it is independent of our subjective cognition, there is nothing to say about it. It is unknowable. All we can hope to truly know is the subjective side of the story. Despite this, Kant still wants to uncover the ways in which the subjective sources of cognition have objective validity. Transcendental conditions are necessary and universal, so although they are subjectively sourced, they should apply objectively to all possible experiences.