stincts and behaviour of a single individual, who himself, as
the very name implies, is essentially indivisible.

To this protest--borrowed from metaphysics--we may
reply that certainly an individual cannot be broken up into
independent pieces. But no less certainly the various
aspects of his behaviour can and must be submitted to
separate consideration. Every science whatever, physical
no less than psychological, is obliged to dissect its subject-
matter, to deal with the different aspects of it in succession,
and finally to bring each of these into relation with all the
rest. Only by first dividing can the scientist eventually
conquer.

In general, a person's total cognitive ability may be re-
garded as an instrument or organ at the disposal of any of
his conative activities. It is this organ, then, that we are
principally about to examine, and with especial reference to
its variations of efficiency from one individual to another.
The conative activities will only be brought within our
scope to the extent that is needful to explain the working
of the organ. But even this much will involve treating
these activities in a far more fundamental manner than is
usual in books on human ability.

-3-