Kant held that careful analysis shows us that any piece of knowledge has two constituents of very diverse origin. It has a _matter_ or material constituent consisting, as Kant held, of certain crude data supplied by sensation, colours, tones of varying pitch and loudness, odours, savours, and the like. It has also a _form_ or formal constituent. Our data, when we know anything at all, are arranged on some definite principle of order. When we recognize an object by the eye or a tune by the ear, we do not apprehend simply so much colour or sound, but colours spread out and forming a pattern or notes following one another in a fixed order. (If you reverse the movement of a gramophone, you get the same notes as before, but you do not get the same tune.) Further, Kant thought it could be shown that the data of our knowledge are a disorderly medley and come to us from without, being supplied by things which exist and are what they are equally whether any one perceives them or not, but the element of form, pattern, or order is put into them by our own minds in the act of knowing them. Our minds are so constructed that we _can_ only perceive things or think of them as connected by certain definite principles of orderly arrangement. This, he thought, explains the indubitable fact that we can sometimes know universal propositions to be true without needing to examine all the individual instances. I can know for certain that in every triangle the greater angle is subtended by the greater side, or that every event has a definite cause among earlier events, though I cannot examine all triangles or all events one by one. This is because the postulates of geometry and the law of causality are types of order which my mind _puts_ into the data of its knowledge in the very act of attending to them, and it is therefore certain that I shall never perceive or think anything which does not conform to these types.