The present volume contains three studies which seem to me to be necessary
_prolegomena_ to that analysis of the sexual instinct which must form the
chief part of an investigation into the psychology of sex. The first
sketches the main outlines of a complex emotional state which is of
fundamental importance in sexual psychology; the second, by bringing
together evidence from widely different regions, suggests a tentative
explanation of facts that are still imperfectly known; the third attempts
to show that even in fields where we assume our knowledge to be adequate a
broader view of the phenomena teaches us to suspend judgment and to adopt
a more cautious attitude. So far as they go, these studies are complete in
themselves; their special use, as an introduction to a more comprehensive
analysis of sexual phenomena, is that they bring before us, under varying
aspects, a characteristic which, though often ignored, is of the first
importance in obtaining a clear understanding of the facts: the tendency
of the sexual impulse to appear in a spontaneous and to some extent
periodic manner, affecting women differently from men. This is a tendency
which, later, I hope to make still more apparent, for it has practical and
social, as well as psychological, implications. Here--and more especially
in the study of those spontaneous solitary manifestations which I call
auto-erotic--I have attempted to clear the ground, and to indicate the
main lines along which the progress of our knowledge in these fields may
best be attained.

It may surprise many medical readers that in the third and longest study I
have said little, save incidentally, either of treatment or prevention.
The omission of such considerations at this stage is intentional. It may
safely be said that in no other field of human activity is so vast an
amount of strenuous didactic morality founded on so slender a basis of