From October 23 to October 27, the scientific world will be celebrating the one-hundredth birthday of Marcellin Berthelot. This great French chemist has not yet achieved the status of a remote historical personality. It was a mere twenty years ago that he died, and some of the leading scholars of today had occasion to engage with him in scientific dispute. Nonetheless, his lifetime is sufficiently removed from the present for us to survey his works and his influence and to construct a clear picture of his significance.