At first glance this might appear to be a cheap, dialectical trick to confound his critics by telling them that “sex” meant all the things they had called by other names. Freud’s _Three Contributions to Sexual Theory_ was saved from being a rhetorical quibble by the virtuosity of his imagination and by the apparent definiteness of the connections which he traced between the various features of childhood development and the patterns of healthy and perverse adult sexuality. Careful analysis of biologically efficacious intercourse shows that it is a complex integration of many acts. It involves a partner of the opposite sex. Its essential feature is an increasing tension until the point of explosive release, followed by perfect relaxation. The male must be sadistic enough to run the risk of hurting the female by injecting the penis in the vagina. The participants must be willing to indulge in all sorts of preliminary play for the sake of heightening the critical tension, involving tongue, lips, nipples, and all the erogenous zones of the body. Comparing the details of this completed pattern of the unambiguously sexual act with the earlier activities of the infant and child, Freud drew a host of analogies. Children indulge in play in sexual postures, exhibit their sexual parts to one another, and take pleasure in sexual peeping; but Freud carried his analysis of the sexuality of children much farther. Child specialists had often remarked that the nursing male child frequently exhibits the phenomenon of an erect penis and a desire to suckle for some time after hunger contractions cease. The general pattern of the sequence hunger-nursing-peaceful relaxation follows the characteristic curve of the sexual act. Freud suggested that inspection of the nursing pattern reveals that the pleasure derived by the child goes far beyond immediate biological necessities. This excess gratification Freud treats as a primitive outcropping of the sexual instinct, which need not be supposed to appear suddenly with the maturation of the glandular apparatus, but may be thought of as growing like the usual biological process by integrating partial components into one complex synthesis.