The appearance of the following pages might suggest an "intellectual biography". My purpose is not, though, to offer such a simple thing (interesting as it might be). Indeed, I would like to follow the evolution of Gauthier's thought not only to show how a thinker evolved from a particular view about a particular problem toward a quite original and suggestive formulation, but also to deepen our comprehension of moral contractarianism and its implications, by means of its contextualization. For this reason, I will focus not on Gauthier's philosophical production as a whole (we will pay little attention to his historical works, for example), but on the papers and works that mark the line toward moral contractarianism as it is found in Morals by Agreement (henceforth MA). The trajectory we are about to go over is not, therefore, only a personal adventure (though it will be displayed this way), but (if I may use this pompous language) the adventure of ideas. This will not be an easy journey. Our focus on the historical development of concepts will prevent us from giving a fully systematic account of every one of them. The unfamiliar reader may be disappointed as we use somewhat strange terms without completely explaining their meaning. We beg acquiescence with our method, hoping that, on the whole, the essential ideas will be understandable without a detailed discussion.