5. The Act of Knowing the World

I will make myself clearer by an example. If I throw a stone horizontally through the air, I perceive it in different places one after the other. I connect these places so as to form a line. Mathematics teaches me to know various kinds of lines, one of which is the parabola. I know the parabola to be a line which is produced when a point moves according to a particular law. If I examine the conditions under which the stone thrown by me moves, I find the path traversed is identical with the line I know as a parabola. That the stone moves just in a parabola is a result of the given conditions and follows necessarily from them. The form of the parabola belongs to the whole phenomenon as much as any other feature of it does. The spirit described above who has no need of the detour of thinking would find itself presented not only a sequence of visual percepts at different points but, as part and parcel of these phenomena, also with the parabolic form of the path which we add to the phenomenon only by thinking.