What is the oath, what is its origin as its purpose if it seems to question the man himself as a political animal? The archaeology of the oath presented in this book tries to answer these questions. Through a first-hand survey of Greek and Roman sources, which highlights the link with the archaic law, the curse, and the names of gods and blasphemy, Agamben locates the origin of the oath in a new perspective, in which it appears as the decisive event in the human genesis as a man, in his becoming human. The oath was able to establish itself as a 'sacrament of power' because it is above all 'the sacrament of language', in which man, who discovered himself as a speaker, decides to link himself to his word and put into play in it his life and his fate.