Number! surely there can be nothing mysterious here; no "law" to be discovered about one, two, three? Well, the next time you shake hands, ask the man what he feels. A hand. Then ask further and he will feel five fingers. Now ask rightly and he will feel any number of distinct spots of pressure. But the real pressures were practically the same all through. Why, then, did he feel first one, then five, then eight, ten, or a dozen? So with the objects we become acquainted with through any of our senses! Why does the same bit of nature now stand before us "one tree," and now a myriad of leaves and branches? Why do the same outer groupings fall into such different inner groupings? Why does not the result of each little nerve of the millions continually played on in eye, ear, and skin stand out by itself, and we have so many million feelings? To explain this: the first time a child opens his eyes he sees, as Professor James says, but "one big, blooming, buzzing confusion." Not till some "whole" (knife) be broken up into parts (blade, handle) and each part be mentally perceived _in immediate succession the one after the other_ can the idea of "twoness" ever be possible to that child. The "twoness" is a feeling of distinct nature apart from the two terms (blade, handle). It rises from the "shock of succession." It is one of the "modified states" wrought by one element on another, which we studied in our first experiment. Once lodged in the mind, the feeling may be remembered and reawakened, like any other. Thereafter the two parts or terms may come before the mind, awaken this feeling of twoness, and _now_ stand side by side, simultaneously and numerically separate. These are the primary laws of number perception. Our experiments illustrate and prove them. Though the nerves lying under a needle point are really several in number, the pressure on them is commonly felt as "one prick." The area is so small that usually, through life, all the nerves have been pressed together. They have not been split up and pressed enough times in succession among themselves for a memory of "twoness" to have been developed among them. But, by proper manipulation, not unlike some of the processes of hypnotism, yet perfectly normal, the "twoness" of some other group of nerves can be yoked to the feeling resulting from the pressure of a particular needle point. Thereupon the one needle will feel like two, as distinctly and clearly as any real two. [Illustration: MEASURING THE TIME REQUIRED FOR VARIOUS MENTAL ACTS.] MENTAL ORIGIN OF DISTANCES AND SPACE.