First and foremost, it is an untenable error to deny that children have a sexual life and to suppose that sexuality only begins at puberty with the maturation of the genitals. On the contrary, from the very first children have a copious sexual life, which differs at many points from what is later regarded as normal. What in adult life is described as "perverse" differs from the normal in these respects: first, by disregarding the barrier of species (the gulf between men and animals), secondly, by overstepping the barrier against disgust, thirdly that against incest (the prohibition against seeking sexual satisfaction from near-blood relations), fourthly that against members of one's own sex and fifthly the transferring of the part played by the genitals to other organs and areas of the body. None of these barriers existed from the beginning; they were only gradually erected in the course of development and education. Small children are free from them. They recognize no frightful gulf between human being and animals; the arrogance with which men separate themselves from animals does not emerge until later.

To begin with, children exhibit no disgust at excreta but acquire this slowly under the pressure of education; they attach no special importance to the distinction between sexes, but attribute the same conformation of the genitals to both; they direct their first sexual lusts and their curiosity to those who are nearest and for other reasons dearest to them - parents, brothers and sisters, or nurses; and finally, they show (what later on breaks through once again at the climax of a love-relation) that they expect to derive pleasure not only from their sexual organs, but that many other parts of the body lay claim to the same sensitivity, afford them analogous feelings of pleasure and can accordingly play the part of genitals. Children may thus be described as "polymorphously perverse", and if these impulses only show traces of activity, that is because on the one hand they are of less intensity compared with those in later life and on the other hand all a child's sexual manifestations are at once energetically suppressed by education.

Introductory Lessons on Psychoanalysis