This book is organized as a commentary following the text of the B-Transcendental Deduction line by line. In so doing, it becomes evident that each step of the Deduction necessarily follows from the preceding step and is grounded in it, although not in the way the steps of a formal-logic deduction are. The primary hypothesis of this book is that the succession of steps is but the unfolding of the Principle of Apperception. The commentary assumes that the entire argument of the B-Deduction consists in a progressive enlargement and enrichment of the Principle of Apperception. The book draws its unity from this assumption, as well as from the strong concatenation of the successive steps. Focusing the monograph on the very narrow problem of the B-Deduction’s argumentative structure enables the author to settle several controversial questions, such as, for instance, those originating in the division of the B-Deduction in two steps, and that of the function of the doctrine of the transcendental subject expounded in paragraphs 24 and 25. Its comprehensive explanation of the Transcendental Deduction ensures that the book will be helpful to students of Kantian Philosophy, while its focus on a single problem will make it useful to specialists. Kant’s B Deduction is part of the Kantian Questions series.