e matter involves already a superior degree of
organization, a degree to which the animal could not have risen, save on
the wings of instinct. So, while nature has frankly evolved in the
direction of instinct in the arthropods, we observe in almost all the
vertebrates the striving after rather than the expansion of
intelligence. It is instinct still which forms the basis of their
psychical activity; but intelligence is there, and would fain supersede
it. Intelligence does not yet succeed in inventing instruments; but at
least it tries to, by performing as many variations as possible on the
instinct which it would like to dispense with. It gains complete
self-possession only in man, and this triumph is attested by the very
insufficiency of the natural means at man's disposal for defense against
his enemies, against cold and hunger. This insufficiency, when we strive
to fathom its significance, acquires the value of a prehistoric
document; it is the final leave-taking between intelligence and
instinct. But it is no less true that nature must have hesitated between
two modes of psychical activity--one assured of immediate success, but
limited in its effects; the other hazardous, but whose conquests, if it
should reach independence, might be extended indefinitely. Here again,
then, the greatest success was achieved on the side of the greatest
risk. _Instinct and intelligence therefore represent two divergent
solutions, equally fitting, of one and the same problem._

There ensue, it is true, profound differences of internal structure
between instinct and intelligence. We shall dwell only on those that
concern our present study. Let us say, then, that instinct and
intelligence imply two radically different kinds of knowledge. But some
explanations are first of all necessary on the subject of consciousness
in general.

It has been asked how far instinct is conscious. Our reply is that there
are a vast number of differences and degrees, that instinct is more or
less conscious in certain cases, unconscious in others. The plant, as we
shall see, has instincts; it is not likely that these are accompanied by
feeling. Even in the animal there is hardly any complex instinct that is
not unconscious in some part at least of its exercise. But here we must
point out a difference, not often noticed, between two kinds of
unconsciousness, viz., that in which consciousness is _absent_, and that
in which consciousness is _nullified_. Both ar