In his Contribution de Montesquieu à la constitution de la science sociale, Émile Durkheim, perhaps the first great thinker to name Montesquieu as the precursor of the new social science, calls attention to an important difficulty in his work. Philosophers before Montesquieu used to derive natural right and political right from one single source. There could be no division between society and its movement on the one hand, and nature and individual moral conduct on the other. Since, for these earlier philosophers, political and natural right derived from the same principle, they shied away from confrontation with one problematic fact: sometimes, natural right and political right indicated two different, not to say contradictory, courses of action. This is tantamount to saying that they refused to decide which course of action the individual, once he is faced with this contradiction, should follow. Unable and unwilling to solve this problem, they came short of a thorough and coherent theory of obligation.