Summary
Kant is finally ready to answer the question of how metaphysics is possible as a science. The answer is: as critique. It is an illegitimate use of Reason to try to use it to know anything beyond the realm of experience. Kant agrees with Hume that it is fundamentally not possible to discover substantive truths other than through experience. But Reason can furnish us with much information about the functioning of the mind and its various faculties. Reason can ask what the case must be for us to experience the world as we do.
Kant closes by addressing reviews of the book, and by observing that his reader will agree that metaphysics has not advanced in the slightest from its inception. And yet, we have a natural tendency towards speculative thinking, towards posing questions that cannot be answered. At the same time, we cannot simply rely on our common sense, which also makes judgments without ever inquiring into why. By turning metaphysics inward, we can save it.
Analysis
Kant’s philosophy, and the Prolegomena in particular, have a strange self-referential quality, in that Kant claims to be preparing the way for a science that doesn’t exist yet, while trying to practice it himself. In the Scholia, Kant now reveals that he has been practicing it all along. By rigorously “critiquing” the concept of metaphysics, by testing its relation to each of the individual faculties, he has been doing precisely the sort of “critical” metaphysics that he thinks should be the basis of all philosophy.
Later philosophers, like Edmund Husserl, have cast Kant as a “phenomenologist,” a philosopher whose investigations begin with the simple fact of the world as it appears to us on a daily basis. Certain aspects of Kant’s argument do have a “psychological” bent: the distinction between subjective perceptions and objective judgments, for example, can be ungenerously categorized as simply that they “feel” different.
But the purpose of the Scholia section is to remind the reader that Kant’s ultimate question and project is not to explain why things appear one way or the other, but rather how knowledge is possible. In his view, philosophy has simply gone ahead and tried to answer all manner of questions without first answering this fundamental one: how is philosophy possible as a science? How can we say for certain that we know what we know?
Though it cannot answer the larger, cosmic questions we are after, Reason can nonetheless answer this one. Knowledge is possible because of the co-operative functioning of the faculties of our mind, each of which plays a crucial role in producing knowledge. The senses give us the pure intuitions of space and time, the understanding furnishes us with its pure concepts, and that Reason regulates the functioning between the two.
