degree on their relative complexity," and instinctive behavior,
he concludes, may be said to comprise "those complex groups of
co-ordinated acts which are, on their first occurrence,
independent of experience; which tend to the well-being of the
individual and the preservation of the race; which are due to the
co-operation of external and internal stimuli; which are
similarly performed by all the members of the same more or less
restricted group of animals; but which are subject to variation,
and to subsequent modification under the guidance of experience."
Such a definition clearly justifies us in speaking of a "sexual
instinct." It may be added that the various questions involved in
the definition of the sexual instinct have been fully discussed
by Moll in the early sections of his _Untersuchungen über die
Libido Sexualis_.

Of recent years there has been a tendency to avoid the use of the
term "instinct," or, at all events, to refrain from attaching any
serious scientific sense to it. Loeb's influence has especially
given force to this tendency. Thus, while Piéron, in an
interesting discussion of the question ("Les Problèmes Actuels de
l'Instinct," _Revue Philosophique_, Oct., 1908), thinks it would
still be convenient to retain the term, giving it a philosophical
meaning, Georges Bohn, who devotes a chapter to the notion of
instinct (_La Naissance de l'Intelligence_, 1909), is strongly in
favor of eliminating the word, as being merely a legacy of
medieval theologians and metaphysicians, serving to conceal our
ignorance or our lack of exact analysis.

It may be said that the whole of the task undertaken in these _Studies_ is
really an attempt to analyze what is commonly called the sexual instinct.