It would be impossible, in a book not exclusively designed for a public of professors, to give a full account of these three dialogues. It is indispensable to describe their drift, because it is here that Diderot figures definitely as a materialist. Diderot was in no sense the originator of the French materialism of the eighteenth century. He was preceded by Maupertuis, by Robinet, and by La Mettrie; and we have already seen that when he composed the Thoughts on the Interpretation of Nature (1754), he did not fully accept Maupertuis's materialistic thesis. Lange has shown that at a very early period in the movement the most consistent materialism was ready and developed, while such leaders of the movement as Voltaire and Diderot still leaned either on deism, or on a mixture of deism and scepticism.[214] The philosophy of D'Alembert's Dream is definite enough, and far enough removed alike from deism and scepticism. [214] _Gesch. d. Materialismus_, i. 309, 310, etc. "The thinking man is like a musical instrument. Suppose a clavecin to have sensibility and memory, and then say whether it would not repeat of itself the airs that you have played on its keys. We are instruments endowed with sensibility and memory. Our senses are so many keys, pressed by the nature that surrounds them, and they often press one another; and this, according to my judgment, is all that passes in a clavecin organised as you and I are organised. "There is only one substance in the world. The marble of the statue makes the flesh of the man, and conversely. Reduce a block of marble to impalpable powder; mix this powder with humus, or vegetable earth; knead them well together; water the mixture; let it rot for a year, two years--time does not count. In this you sow the plant, the plant nourishes the man, and hence the passage from marble to tissue. "Do you see this egg? With that you overturn all the schools of theology and all the temples of the earth. It is an insensible mass before the germ is introduced into it; and, after the germ is introduced, there is still an insensible mass, for the germ itself is only an inert fluid. How does this mass pass to another organisation, to life, to sensibility? By heat. What will produce heat? Movement. What will be the successive effects of movement? First, an oscillating point, a thread that extends, the flesh, the beak, and so forth." Then follows the application of the same ideas to the reproduction of man--a region whither it is not convenient to follow the physiological inquirer. The result as to the formation of the organic substance in man is as unflinching as the materialism of Buechner. But doctor, cries Mdlle. Lespinasse, what becomes of vice and virtue? Virtue, that word so holy in all languages, that idea so sacred among all nations?