This book, though brief, is interesting because its interest is based on the perspective of the Roman world of Greek philosophy and early Christianity without trying to justify one or the other relative. It brings together two lectures on the same day at the Sorbonne: an L Jerphagnon focused on the historical aspect and the Roman world; the other by L Ferry, brilliant and illuminating, seeking to update the break made between the representation of the world showing through Greek philosophy and that of Christianity.