Child of materialism and positivism, Courbet was without a doubt one of the most complex painters of the nineteenth century. Symbolising the rejection of traditions, Courbet did not hesitate to confront the public with the truth by liberating painting of conventional rules. He became from then on the leader of pictorial realism. This text on Courbet is the result of years of intensive research and traces with great care contradictory testimonies, the praises as well as the negative critics this controversial painter had during his times. By his precision as an art historian, Georges Riat sheds new light on the work of this artist who created a real separation with the academicism of the time.