Plato's Symposium contains various myths dealing with gender and the erotic, among them Aristophanes' account of the three original sexes, which are here treated from the standpoint of modern science. In particular we see how, since the 19th century, sexology and psychoanalysis have updated concepts of a third sex and androgyny. Similarities with positions in antiquity demonstrate the relevance and force of the general propositions of myths. Differences appear to imply the effective presence of other myths of Judeo-Christian origin. All (...) things considered, the ancient tensions between Aristophanes' and Socrates' attitude are still at work. It is from that viewpoint that the conceptual relationships between androgyny and the third sex are examined. (shrink)