The critic and philosopher Hippolyte Taine is presented here as one of the pioneers of the theory of the unconscious in European social thought: a source of the more explicit writings on unconscious motivation in the works of Nietzsche, Pareto, and others. Preceding forms of French liberalism – particularly those of Guizot and Cousin – had depended upon an underlying belief in a number of ideas – in God, in our ability to understand his will, and in reason. A representative regime would be able to mobilize rationality in society and give it effective sovereignty. Taine's life can be interpreted as one of increasing conservatism, but it was consistent in his rejection of such a conception of rationality; first through his technical philosophy, then through the discussion of psychological motivation in mass political movements set out in the Origines de la France contemporaine. It is argued that such a rejection of rationalism was a crucial first step in the elaboration of new forms of liberalism – technocratic, welfarist, and economically individualist. Taine's work represents the passage from one type of liberal theory to another at a crucial moment in French history, the consolidation of universal male suffrage as a foundation of the Third Republic.