[Footnote 3:  Here Kant is guilty of the fault which he himself has censured, of confusing the physical and transcendental meanings of “in itself.”  He forgets that the thing, if it is momentarily not intuited or represented by me, and therefore is not immediately given for me as an individual, is nevertheless still present for me as man, is mediately given, that is, is discoverable by future search.  That which is without my present consciousness is not for this reason without all human consciousness.  In fact, Kant often overlooks the distinction between actual and possible intuition, so that for him the “objects” of the latter slip out of space and time and into the thing in itself.  To the “transcendental object we may ascribe the extent and connection of our possible perceptions, and say that it is given in itself before all experience.”  In it “the real things of the past are given.”]

After the possibility and the legitimacy of synthetic judgments a priori have been proved for pure mathematics upon the basis of the pure intuitions, there emerges, in the second place, the problem of the possibility of a priori syntheses in pure natural science, or the question, Do pure concepts exist?  And after this has been answered in the affirmative, the further questions come up, Is the application of these, first, to phenomena, and second, to things in themselves, possible and legitimate, and how far?

%(b) The Concepts and Principles of the Pure Understanding (Transcendental Analytic).%—­Sensations, in order to become “intuition” or the perception of a phenomenon, needed to be ordered in space and time; in order to become “experience” or a unified knowledge of objects, intuitions need a synthesis through concepts.  In order to objective knowledge the manifold of intuition (already ordered by its arrangement in space and time) must be connected in the unity of the concept.  Sensibility gives the manifold to be connected, the understanding the connecting unity.  The former is able to intuit only, the latter only to think; knowledge can arise only as the result of their union.  Intuitions depend on affections, concepts on functions, that is, on unifying acts of the understanding.

To discover the pure forms of thought it is necessary to isolate the understanding, just as an isolation of the sensibility was necessary above in order to the discovery of the pure forms of intuition.  We obtain the elements of the pure knowledge of the understanding by rejecting all that is intuitive and empirical.  These elements must be pure, must be concepts, further, not derivative or composite, but fundamental concepts, and their number must be complete.  This completeness is guaranteed only when the pure concepts or categories are sought according to some common principle, which assigns to each its position in the connection of the whole, and not (as with Aristotle) collected by occasional, unsystematic inquiries undertaken at random.  The table of