'Auto erotism,' ... spontaneous solitary sexual phenomena of which genital excitement during sleep may be said to be the type.

Among all types of sexual activity, masturbation is ... the one in which the female most frequently reaches orgasm.

And as I had my father's kind of mind–which was also his mother's–I learned that the mind is not sex-typed.

Being the inventor of sex would seem to be a sufficient distinction for a creature just barely large enough to be seen by the naked eye.
[Comment about Volvox, a freshwater green algae, which appears indetermimately plantlike and animal-like during its reproductive cycle.]

Courtship, properly understood, is the process whereby both the male and the female are brought into that state of sexual tumescence which is a more or less necessary condition for sexual intercourse. The play of courtship cannot, therefore, be considered to be definitely brought to an end by the ceremony of marriage; it may more properly be regarded as the natural preliminary to every act of coitus.

Every animal is sad after coitus except the human female and the rooster.

Few males achieve any real freedom in their sexual relations even with their wives. Few males realise how badly inhibited they are on these matters.

I conclude that the musical notes and rhythms were first acquired by the male or female progenitors of mankind for the sake of charming the opposite sex.

I regard sex as the central problem of life. And now that the problem of religion has practically been settled, and that the problem of labor has at least been placed on a practical foundation, the question of sex—with the racial questions that rest on it—stands before the coming generations as the chief problem for solution. Sex lies at the root of life, and we can never learn to reverence life until we know how to understand sex.

On the one hand, then, in the reproductive functions proper—menstruation, defloration, pregnancy and parturition—woman is biologically doomed to suffer. Nature seems to have no hesitation in administering to her strong doses of pain, and she can do nothing but submit passively to the regimen prescribed. On the other hand, as regards sexual attraction, which is necessary for the act of impregnation, and as regards the erotic pleasures experienced during the act itself, the woman may be on an equal footing with the man.

Philosophy is to science as pornography is to sex: it is cheaper, easier and some people prefer it.

Reproduction is so primitive and fundamental a function of vital organisms that the mechanism by which it is assured is highly complex and not yet clearly understood. It is not necessarily connected with sex, nor is sex necessarily connected with reproduction.

Sex appeal is a matter of chemistry, but you don't have to be a chemist to fins the formula.

Sex is the best form of fusion at room temperature.

Sexual instinct—as emotion, idea, and impulse—is a function of the cerebral cortex. Thus far no definite region of the cortex has been proved to be exclusively the seat of sexual sensations and impulses.

The male's difficulties in his sexual relations after marriage include a lack of facility, of ease, or of suavity in establishing rapport in a sexual situation.

The modesty of women, which, in its most primitive form among animals, is based on sexual periodicity, is, with that periodicity, an essential condition of courtship.

The range of variation in the female far exceeds the range of variation in the male.

The second great channel through which the impulse towards the control of procreation for the elevation of the race is entering into practical life is by the general adoption, by the educated—of methods for the prevention of conception except when conception is deliberately desired.

The weakness of men in comparison with women lies in the great intensity of their sexual desires. Man becomes dependent upon woman, and the more, the weaker and more sensual he becomes; and this just in proportion as he becomes neuropathic.

There is a tendency to consider anything in human behavior that is unusual, not well known, or not well understood, as neurotic, psychopathic, immature, perverse, or the expression of some other sort of psychologic disturbance.

Too early and perverse sexual satisfaction injures not merely the mind, but also the body; inasmuch as it induces neuroses of the sexual apparatus (irritable weakness of the centres governing erection and ejaculation; defective pleasurable feeling in coitus), while, at the same time, it maintains the imagination and libido in continuous excitement.

What we call 'Progress' is the exchange of one Nuisance for another Nuisance.

While up to this time contrary sexual instinct has had but an anthropological, clinical, and forensic interest for science, now, as a result of the latest investigations, there is some thought of therapy in this incurable condition, which so heavily burdens its victims, socially, morally, and mentally. A preparatory step for the application of therapeutic measures is the exact differentiation of the acquired from the congenital cases; and among the latter again, the assignment of the concrete case to its proper position in the categories that have been established empirically.

With respect of the development of physiological love, it is probable that its nucleus is always to be found in an individual fetich (charm) which a person of one sex exercises over a person of the opposite sex.