ing 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.]

Now, to secure this, it is not enough that the sensorium should be
materially continuous, or that a "spiritual substance" or a
"transcendental ego" should persist in time to receive the second
sensation after having received and registered the first. A perfectly
elastic sensorium, a wholly unchanging soul, or a quite absolute ego
might remain perfectly identical with itself through various experiences
without collating them. It would then remain, in fact, more truly and
literally identical than if it were modified somewhat by those
successive shocks. Yet a sensorium or a spirit thus unchanged would be
incapable of memory, unfit to connect a past perception with one present
or to become aware of their relation. It is not identity in the
substance impressed, but growing complication in the phenomenon
presented, that makes possible a sense of diversity and relation between
things. The identity of substance or spirit, if it were absolute, would
indeed prevent comparison, because it would exclude modifications, and
it is the survival of past modifications within the present that makes
comparisons possible. We may impress any number of forms successively on
the same water, and the identity of the substance will not help those
forms to survive and accumulate their effects. But if we have a surface
that retains our successive stampings we may change the substance from
wax to plaster and from plaster to bronze, and the effects of our labour
will survive and be superimposed upon one another. It is the actual
plastic form in both mind and body, not any unchanging substance or
agent, that is efficacious in perpetuating thought and gathering
experience.

[Sidenote: Example of the sun.]

Were not Nature and all h