There’s been a lot of hot air expended on the Web over the recently released study that purports to break down the 237 reasons why women have sex. (I like Tanya Gold’s snarky take at the Guardian.) Of course, pondering human sexuality is nothing new… as these Cosimo Classics demonstrate.

Three Contributions to the Theory of Sex: Austrian psychiatrist Sigmund Freud (1856-1939) was a pioneer in the study of human sexuality and the impact of sexual desire on human behavior, and this 1905 work is considered among his most important contributions to the field. This is the source of such concepts as penis envy, castration anxiety, and the Oedipus complex that we take for granted as fundamental to understanding human psychology. In the three essays here — “The Sexual Aberrations,” “Infantile Sexuality,” and “The Transformations of Puberty” — Freud sets out a theory of human sexuality that continues to influence us today.

Sex as Symbol: The Ancient Light in Modern Psychology: How does gender and the sex drive manifest itself across human cultures? How is the dual nature of humanity — male and female, spiritual and physical, animal and divine — expressed in the tangible world? Alvin Boyd Kuhn (1880–1963), a prominent proponent of the early 20th-century doctrine of theosophy, which sought to find the universal truths that underlie all human religions, here explores the hidden connections across cultures that unify rites and customs found around the globe: circumcision, the secondary status of women, myths about communion with deities, and more. In fluid prose that approaches a stream-of-consciousness reverie, this 1945 treatise seeks to uncover a fundamental basis for human ideas about sex, gender, and love.

Sane Sex Life and Sane Sex Living: Despite its rather staid subtitle — “Some Things That All Sane People Ought to Know About Sex Nature and Sex Functioning; Its Place in the Economy of Life, Its Proper Training and Righteous Exercise” — this 1919 volume may well be one of the most forthright books about human sexuality written in the pre-Joy of Sex era. Actively campaigning against societally sanctioned ignorance, medical doctor Harland William Long (b. 1869) uses clinical yet passionate language in his call for men and women alike to be fully educated about their own bodies as well as those of their lovers. This straightforward work is still startling today in its advocacy of detailed explanation not just of the physical act of sex but of the emotional art of lovemaking, its advocacy of masturbation, and its insistence on celebrating the uniquely spiritual, though not necessarily religious, aspects of love and marriage. This is must-reading for anyone who believes that frank and honest sex education is an invention of the 1960s — and for anyone who wishes to contest that misbelief.