But why do so many people dream that they are able to fly? Psychoanalysis answers this question by stating that to fly or to be a bird in the dream is only a concealment of another wish, to the recognition of which one can reach by more than one linguistic or objective bridge. When the inquisitive child is told that a big bird like the stork brings the little children, when the ancients have formed the phallus winged, when the popular designation of the sexual activity of man is expressed in German by the word "to bird" (vögeln), when the male member is directly called _l'uccello_ (bird) by the Italians, all these facts are only small fragments from a large collection which teaches us that the wish to be able to fly signifies in the dream nothing more or less than the longing for the ability of sexual accomplishment. This is an early infantile wish. When the grown-up recalls his childhood it appears to him as a happy time in which one is happy for the moment and looks to the future without any wishes, it is for this reason that he envies children. But if children themselves could inform us about it they would probably give different reports. It seems that childhood is not that blissful Idyl into which we later distort it, that on the contrary children are lashed through the years of childhood by the wish to become big, and to imitate the grown ups. This wish instigates all their playing. If in the course of their sexual investigation children feel that the grown up knows something wonderful in the mysterious and yet so important realm, what they are prohibited from knowing or doing, they are seized with a violent wish to know it, and dream of it in the form of flying, or prepare this disguise of the wish for their later flying dreams. Thus aviation, which has attained its aim in our times, has also its infantile erotic roots. By admitting that he entertained a special personal relation to the problem of flying since his childhood, Leonardo bears out what we must assume from our investigation of children of our times, namely, that his childhood investigation was directed to sexual matters. At least this one problem escaped the repression which has later estranged him from sexuality. From childhood until the age of perfect intellectual maturity this subject, slightly varied, continued to hold his interest, and it is quite possible that he was as little successful in his cherished art in the primary sexual sense as in his desires for mechanical matters, that both wishes were denied to him.