The child sucking at his mother's breast becomes [in Freud] the paradigm for all sexual pleasure in later life, and Freud asserts that to begin with, sexual activity props itself upon the vital function of nourishment by the mother's milk. Thumb-sucking and the sensual smacking of the lips then gives Freud the three characteristics of infantile sexual manifestation. These are: (1) Propping, at the origin, upon a vital somatic function; (2) auto-eroticism, or the lack of a sexual object; (3) domination of sexual aim by an erotogenic zone; here, the lips. It is at this point in his discussion that Freud makes one of his uncanniest leaps, relying on his extraordinary trope of propping. While the propping of the sexual drive upon the vial order still continues, the sexual drive finds its first object outside the infant's body in the mother's breast, and the milk ensuing from it. Suddenly Freud surmises that just at the time the infant is capable of forming a total idea of the mother, quite abruptly the infant loses the initial object of the mother's breast, and tragically is thrown back on auto-eroticism. Consequently, the sexual drive has no proper object again until after the latency period has transpired, and adolescence begins. Hence that dark and infinitely suggestive Freudian sentence: "The finding of an object is in fact a re-finding of it."
Thus human sexuality, alas, on this account has not had, from its very origins, any real object. The only real object was milk, which belongs to the vital order. Hence the sorrows and the authentic anguish of all human erotic quest, hopelessly seeking to rediscover an object, which was never the true object anyway.