By "the form of intuition," Kant meant, as he has repeatedly explained, the _plural quality_ of space and time. Space is made of _spaces_; time of _times_; and the plural contents (always such) of matter can only exist under the plural contents of space and time--that is, in sections of space and sequences of time, these sections and sequences being the intrinsic character, the divisible quality, the essential "form" of space and time as total units or completed things. And the nature of space and time need not be anything more _objective_ than the nature of matter in general, but can be derived, too, from "the mode in which the subject is affected." "But," says Kant, "_all conjunction_" is "an act of the understanding," and "can not be contained in the pure form of sensuous intuition"; by which he means that time could never be a conjunct of times, space a conjunct of spaces, nor a stone the conjunct of its properties--each a "synthesis" of a "manifold content"--unless made so by the synthetical unity of _a priori_ mind. Kant attributes "_unconscious_" action to the "_understanding_"--the unconscious action of "conjunction" or "synthesis." His phrase has been a perpetual stumbling-block to his readers, but he meant exactly what he said. Unconscious mental synthesis is what he afterward designated as "the synthesis of _apprehension_." "By the term _synthesis_ of apprehension [said he], I understand the combination of the manifold in an empirical intuition, whereby perception, that is, empirical consciousness of the intuition (as phenomenon), is possible."