If this sounds paradoxical to anyone, let him think of analytical geometry. The identical figures which Euclid defined by intrinsic relations were defined by Descartes by the relations of their points to adventitious co-ordinates, the result being an absolutely different and vastly more potent way of handling curves. All our conceptions are what the Germans call denkmittel, means by which we handle facts by thinking them. Experience merely as such doesn't come ticketed and labeled, we have first to discover what it is. Kant speaks of it as being in its first intention a gewuehl der erscheinungen, a rhapsodie der wahrnehmungen, a mere motley which we have to unify by our wits. What we usually do is first to frame some system of concepts mentally classified, serialized, or connected in some intellectual way, and then to use this as a tally by which we 'keep tab' on the impressions that present themselves. When each is referred to some possible place in the conceptual system, it is thereby 'understood.' This notion of parallel 'manifolds' with their elements standing reciprocally in 'one-to-one relations,' is proving so convenient nowadays in mathematics and logic as to supersede more and more the older classificatory conceptions. There are many conceptual systems of this sort; and the sense manifold is also such a system. Find a one-to-one relation for your sense-impressions ANYWHERE among the concepts, and in so far forth you rationalize the impressions. But obviously you can rationalize them by using various conceptual systems. The old common-sense way of rationalizing them is by a set of concepts of which the most important are these: Thing; The same or different; Kinds; Minds; Bodies; One Time; One Space; Subjects and attributes; Causal influences; The fancied; The real. We are now so familiar with the order that these notions have woven for us out of the everlasting weather of our perceptions that we find it hard to realize how little of a fixed routine the perceptions follow when taken by themselves. The word weather is a good one to use here. In Boston, for example, the weather has almost no routine, the only law being that if you have had any weather for two days, you will probably but not certainly have another weather on the third. Weather-experience as it thus comes to Boston, is discontinuous and chaotic. In point of temperature, of wind, rain or sunshine, it MAY change three times a day. But the Washington weather-bureau intellectualizes this disorder by making each successive bit of Boston weather EPISODIC. It refers it to its place and moment in a continental cyclone, on the history of which the local changes everywhere are strung as beads are strung upon a cord.