The word 'bisexuality', unknown to the ancients, is used here in two senses to indicate an individual with male and female sex organs or who copulates with people of both sexes. The phenomenon of bisexuality is then analysed with reference to the Greek myth of Hermaphrodite, a 'bisexual' being, born of a nymph's love for a young man of divine descent: in the guise of a fable, the myth recounts the birth of a 'monster', who raises a question-mark over the (...) fundamental rule of the division between the sexes. As regards behaviour, the paper then shows that in both Greece and Rome bisexual behaviour was the rule for men. The concept of 'homosexuality', in contrast to heterosexuality, was not introduced till the Christian era, and then not without difficulty. Condemnation of the practice as 'against nature' began with the emperor Justinian in the 6th century. (shrink)