Intelligence is accordingly conditioned by a modification of both structure and consciousness by dint of past events. To be aware that a second stroke is not itself the first, I must retain something of the old sensation. The first must reverberate still in my ears when the second arrives, so that this second, coming into a consciousness still filled by the first, is a different experience from the first, which fell into a mind perfectly empty and unprepared. Now the newcomer finds in the subsisting One a sponsor to christen it by the name of Two. The first stroke was a simple 1. The second is not simply another 1, a mere iteration of the first. It is 1^{1}, where the coefficient represents the reverberating first stroke, still persisting in the mind, and forming a background and perspective against which the new stroke may be distinguished. The meaning of “two,” then, is “this after that” or “this again,” where we have a simultaneous sense of two things which have been separately perceived but are identified as similar in their nature. Repetition must cease to be pure repetition and become cumulative before it can give rise to the consciousness of repetition. The first condition of counting, then, is that the sensorium should retain something of the first impression while it receives the second, or (to state the corresponding mental fact) that the second sensation should be felt together with a survival of the first from which it is distinguished in point of existence and with which it is identified in point of character. [Sidenote: No identical agent needed.]