According to Freud, "Elimination of clitoral sexuality is a necessary precondition for the development of femininity, since it is immature and masculine in its nature." Freud postulated the concept of "vaginal orgasm" as separate from clitoral orgasm, achieved by external stimulation of the clitoris. In 1905, he stated that clitoral orgasms are purely an adolescent phenomenon and that, upon reaching puberty, the proper response of mature women is a change-over to vaginal orgasms, meaning orgasms without any clitoral stimulation. This theory has been criticized on the grounds that Freud provided no evidence for this basic assumption, and because it made many women feel inadequate when they could not achieve orgasm via vaginal intercourse alone.