The Comte de Saint-Simon, who wrote these words in 1814, was one of the liberal nobles who had imbibed the ideas of the Voltairian age and sympathised with the spirit of the Revolution. In his literary career from 1803 to his death in 1825 he passed through several phases of thought, [Footnote: They are traced in G. Weill's valuable monograph, Saint-Simon et son oeuvre, 1894.] but his chief masters were always Condorcet and the physiologists, from whom he derived his two guiding ideas that ethics and politics depend ultimately on physics and that history is progress. Condorcet had interpreted history by the progressive movement of knowledge. That, Saint-Simon said, is the true principle, but Condorcet applied it narrowly, and committed two errors. He did not understand the social import of religion, and he represented the Middle Ages as a useless interruption of the forward movement. Here Saint-Simon learned from the religious reaction. He saw that religion has a natural and legitimate social role and cannot be eliminated as a mere perversity. He expounded the doctrine that all social phenomena cohere. A religious system, he said, always corresponds to the stage of science which the society wherein it appears has reached; in fact, religion is merely science clothed in a form suitable to the emotional needs which it satisfies. And as a religious system is based on the contemporary phase of scientific development, so the political system of an epoch corresponds to the religious system. They all hang together. Medieval Europe does not represent a temporary triumph of obscurantism, useless and deplorable, but a valuable and necessary stage in human progress. It was a period in which an important principle of social organisation was realised, the right relation of the spiritual and temporal powers. It is evident that these views transformed the theory of Condorcet into a more acceptable shape. So long as the medieval tract of time appeared to be an awkward episode, contributing nothing to the forward movement but rather thwarting and retarding it, Progress was exposed to the criticism that it was an arbitrary synthesis, only partly borne out by historical facts and supplying no guarantees for the future. And so long as rationalists of the Encyclopaedic school regarded religion as a tiresome product of ignorance and deceit, the social philosophy which lay behind the theory of Progress was condemned as unscientific; because, in defiance of the close cohesion of social phenomena, it refused to admit that religion, as one of the chief of those phenomena, must itself participate and co-operate in Progress.