Questions asked by Greek philosophy and science - how do we come to be? How do we grow? When are we recognizably human? - are addressed with new intensity today. Modern embryology has changed the methods of enquiry and given new knowledge. Public interest and concern are high because medical applications of new knowledge offer benefits and yet awaken ancestral fears. The law and politics are called upon to secure the benefits without realizing the fears. Philosophers and theologians are involved once again. In this volume some of the world's authorities on the subject trace the tradition of enquiry over two and a half thousand years. The answers given in related cultures - Greek, Latin, Jewish, Arabian, Islamic, Christian - reflected the purposes to be served at different times, in medical practice, penitential discipline, canon law, common law, human feeling. But the terms in which the questions were discussed were those set down by the Greeks and transmitted through the Arabic authors to medieval Europe.