directly in the Encyclopedia. In the Interpretation de la nature (1754) we find ideas concerning the continuous evolution of life on the earth which are very similar to those of La Mettrie. He was profoundly influenced by Leibnitz, especially in the matter of his emphasis of the concepts of continuity and force. The two dialogues, written in 1769, but not published until 1830, Entretien entre d'Alembert et Diderot and Reve d'Alembert, contain his most ingenious ideas. In direct contradiction of La Mettrie and Holbach, Diderot denies that the psychical processes can be adequately explained as a mere effect of the interaction of material elements. A transposition of atoms can never produce consciousness. The only possible explanation of the origin of psychic life is on the presupposition of the presence of germs or dispositions in the lower orders which can be developed to conscious life in the higher orders by means of a process of progressive integration. Diderot attributes sensibility to everything in nature, but he makes a distinction between potential and actual sensibility (sensibilite inerte, sensibilite active). He likewise emphasizes the difficulty of conceiving how a unitary consciousness could be constructed from a great variety of psychical elements. He does not solve the problem. But he seems inclined to adhere so tenaciously to the idea of continuity, as to leave no room for any actually distinct elements.
2. Jean Jacques Rousseau (1712-1778) was intimately associated with the Encyclopedists for a while. His rupture with them—to which, besides their fundamental differences, personal motives certainly contributed not a little—was an event in the history of civilization, a sign that a new problem was forcing its way to the surface. Just as Hume's problem pertained to the possibility of
