All our knowledge begins with sense, proceeds thence to understanding, and ends with reason, beyond which nothing higher can be discovered in the human mind for elaborating the matter of intuition and subjecting it to the highest unity of thought. At this stage of our inquiry it is my duty to give an explanation of this, the highest faculty of cognition, and I confess I find myself here in some difficulty. Of reason, as of the understanding, there is a merely formal, that is, logical use, in which it makes abstraction of all content of cognition; but there is also a real use, inasmuch as it contains in itself the source of certain conceptions and principles, which it does not borrow either from the senses or the understanding. The former faculty has been long defined by logicians as the faculty of mediate conclusion in contradistinction to immediate conclusions (consequentiae immediatae); but the nature of the latter, which itself generates conceptions, is not to be understood from this definition. Now as a division of reason into a logical and a transcendental faculty presents itself here, it becomes necessary to seek for a higher conception of this source of cognition which shall comprehend both conceptions. In this we may expect, according to the analogy of the conceptions of the understanding, that the logical conception will give us the key to the transcendental, and that the table of the functions of the former will present us with the clue to the conceptions of reason. In the former part of our transcendental logic, we defined the understanding to be the faculty of rules; reason may be distinguished from understanding as the faculty of principles. The term principle is ambiguous, and commonly signifies merely a cognition that may be employed as a principle, although it is not in itself, and as regards its proper origin, entitled to the distinction. Every general proposition, even if derived from experience by the process of induction, may serve as the major in a syllogism; but it is not for that reason a principle. Mathematical axioms (for example, there can be only one straight line between two points) are general à priori cognitions, and are therefore rightly denominated principles, relatively to the cases which can be subsumed under them. But I cannot for this reason say that I cognize this property of a straight line from principles—I cognize it only in pure intuition. Cognition from principles, then, is that cognition in which I cognize the particular in the general by means of conceptions. Thus every syllogism is a form of the deduction of a cognition from a principle. For the major always gives a conception, through which everything that is subsumed under the condition thereof is cognized according to a principle. Now as every general cognition may serve as the major in a syllogism, and the understanding presents us with such general à priori propositions, they may be termed principles, in respect of their possible use.