may be easily seen that sentiment destitute of all, even unconscious,
ideas can have no influence upon the result, for knowledge can only
follow upon an idea. A presentiment that sounds in consonance with
our consciousness can indeed, under certain circumstances, become
tolerably definite, so that in the case of man it can be expressed in
thought and language; but experience teaches us that even among
ourselves this is not so when instincts special to the human race
come into play; we see rather that the echo of our unconscious
knowledge which finds its way into our consciousness is so weak that
it manifests itself only in the accompanying feelings or frame of
mind, and represents but an infinitely small fraction of the sum of
our sensations. It is obvious that such a faintly sympathetic
consciousness cannot form a sufficient foundation for a
superstructure of conscious deliberation; on the other hand,
conscious deliberation would be unnecessary, inasmuch as the process
of thinking must have been already gone through unconsciously, for
every faint presentiment that obtrudes itself upon our consciousness
is in fact only the consequence of a distinct unconscious knowledge,
and the knowledge with which it is concerned is almost always an idea
of the purpose of some instinctive action, or of one most intimately
connected therewith. Thus, in the case of the stag-beetle, the
purpose consists in the leaving space for the growth of the horns;
the means, in the digging the hole of a sufficient size; and the
unconscious knowledge, in prescience concerning the future
development of the horns.

Lastly, all instinctive actions give us an impression of absolute
security and infallibility. With instinct the will is never
hesitating or weak, as it is when inferences are being drawn
consciously. We never find instinct making mistakes; we cannot,