"Porneia" means fornication, unchastity, desire for another's body. Drawing on Roman and Greek works of science, medicine, gynaecology and law, and on Christian and pagan theology, the author discovers the intimate fears, passions, superstitions and ambitions of the people of the Mediterranean world during the first four centuries AD. The first part of the book describes Roman notions of male and female sexuality; attitudes to fertility, inheritance, child care and training; legal restraints on sexual behaviour; concubinage and divorce; and the extraordinary rituals of orgy, castration and sacrifice associated with ancient rites of fertility and spirituality. It lends support to the view that the sexual problems of antiquity are in many respects almost exactly those of the contemporary West, from fear of impotence to the concern of parents about teenage misbehaviour. The second part of the work is concerned with the impact of Christian ideas upon a settled pagan tradition. Abstinence, once associated with the enhancement of fertility, becomes the key to salvation. The first monastic regimes, and the means by which men and women curtailed and overcame their desire for one another, are described in detail. Centuries of concern for fertility became, in this revolutionary period, an obsession with chastity in the present world and a secure place in the next.