Whether we accept or question Comte’s strong description of Diderot as the greatest genius of the eighteenth century, it is at least undeniable that he was the one member of the great party of illumination with a real title to the name of thinker.  Voltaire and Rousseau were the heads of two important schools, and each of them set deep and unmistakable marks both on the opinion and the events of the century.  It would not be difficult to show that their influence was wider than that of the philosopher who discerned the inadequateness of both.  But Rousseau was moved by passion and sentiment; Voltaire was only the master of a brilliant and penetrating rationalism.  Diderot alone of this famous trio had in his mind the idea of scientific method; alone showed any feeling for a doctrine, and for large organic and constructive conceptions.  He had the rare faculty of true philosophic meditation.  Though immeasurably inferior both to Voltaire and Rousseau in gifts of literary expression, he was as far their superior in breadth and reality of artistic principle.  He was the originator of a natural, realistic, and sympathetic school of literary criticism.  He aspired to impose new forms upon the drama.  Both in imaginative creation and in criticism, his work was a constant appeal from the artificial conventions of the classic schools to the actualities of common life.  The same spirit united with the tendency of his philosophy to place him among the very few men who have been great and genuine observers of human nature and human existence.  So singular and widely active a genius may well interest us, even apart from the important place that he holds in the history of literature and opinion.

CHAPTER II.

YOUTH.

Denis Diderot was born at Langres in 1713, being thus a few months younger than Rousseau (1712), nearly twenty years younger than Voltaire (1694), nearly two years younger than Hume (1711), and eleven years older than Kant (1724).  His stock was ancient and of good repute.  The family had been engaged in the great local industry, the manufacture of cutlery, for no less than two centuries in direct line.  Diderot liked to dwell on the historic prowess of his town, from the days of Julius Caesar and the old Lingones and Sabinus, down to the time of the Great Monarch.  With the taste of his generation for tracing moral qualities to a climatic source, he explained a certain vivacity and mobility in the people of his district by the great frequency and violence of its atmospheric changes from hot to cold, from calm to storm, from rain to sunshine.  “Thus they learn from earliest infancy to turn to every wind.  The man of Langres has a head on his shoulders like the weathercock at the top of the church spire.  It is never fixed at one point; if it returns to the point it has left, it is not to stop there.  With an amazing rapidity in their movements, their desires, their plans, their fancies, their ideas, they are cumbrous in speech.  For myself, I belong to my country side.”  This was thoroughly true.  He inherited all the versatility of his compatriots, all their swift impetuosity, and something of their want of dexterity in expression.