ends proposed to itself by the instinct.

The psychical mechanism of this constant connection must also be
looked for. It may help us here to turn to the piano for an
illustration. The struck keys are the motives, the notes that sound
in consequence are the instincts in action. This illustration might
perhaps be allowed to pass (if we also suppose that entirely
different keys can give out the same sound) if instincts could only
be compared with DISTINCTLY TUNED notes, so that one and the same
instinct acted always in the same manner on the rising of the motive
which should set it in action. This, however, is not so; for it is
the blind unconscious purpose of the instinct that is alone constant,
the instinct itself--that is to say, the will to make use of certain
means--varying as the means that can be most suitably employed vary
under varying circumstances.

In this we condemn the theory which refuses to recognise unconscious
purpose as present in each individual case of instinctive action.
For he who maintains instinct to be the result of a mechanism of
mind, must suppose a special and constant mechanism for each
variation and modification of the instinct in accordance with
exterior circumstances, {97} that is to say, a new string giving a
note with a new tone must be inserted, and this would involve the
mechanism in endless complication. But the fact that the purpose is
constant notwithstanding all manner of variation in the means chosen
by the instinct, proves that there is no necessity for the
supposition of such an elaborate mental mechanism--the presence of an
unconscious purpose being sufficient to explain the facts. The
purpose of the bird, for example, that has laid her eggs is constant,
and consists in the desire to bring her young to maturity. When the