reached (in the _Conversation between
D'Alembert and Diderot_, and _D'Alembert's Dream_, written in 1769, but not
published until 1830, in vol. iv. of the _Memoires, Correspondance, et
Ouvrages Inedits de Diderot_) the position of naturalistic monism--there
exists but one great individual, the All. Though he had formerly
distinguished thinking substance from material substance, and had based the
immortality of the soul on the unity of sensation and the unity of the ego,
he now makes sensation a universal and essential property of matter
(_la pierre sent_), declares the talk about the simplicity of the
soul metaphysico-theological nonsense, calls the brain a self-playing
instrument, ridicules self-esteem, shame, and repentance as the absurd
folly of a being that imputes to itself merit or demerit for necessary
actions, and recognizes no other immortality than that of posthumous fame.
But even amid these extreme conclusions, his enthusiasm for virtue remains
too intense to allow him to assent to the audacious theories of La Mettrie
and Helvetius.

[Footnote 1: _Works_ in twenty-two vols., Paris, Briere, 1821; latest
edition, 1875 _seq_. Cf. on Diderot the fine work by Karl Rosenkranz,
_Diderots Leben und Werke_, 1866.]

French natural science also tended toward materialism. Buffon _(Natural
History_, 1749 _seq_) endeavors to facilitate the mechanical explanation
of the phenomena of life by the assumption of living molecules, from
which visible organisms are built up. Robinet (_On Nature_, 1761 _seq_.),
availing himself of Spinozistic and Leibnitzian conceptions, goes still
further, in that he endows every particle of matter with sensation, looks
on the whole world as a succession of living beings with increasing
mentality, and subjects the interaction of the material and psychical sides
of the individual, as well as the relation of pleasure and pain in the
universe, to a law of harmonious compensation.

The _System of Nature_, 1770, which bore on its title page the name of
Mirabaud, who had died 1760, proceeded from the company of freethinkers
accustomed to meet in the hospitable house of Baron von Holbach (died
1789), a native of the Palatinate. Its real author was Holbach himself,
although his friends Diderot, Naigeon, Lagrange, the mathematician, and the
clever Grimm (died 1807) seem to have co-operated in the preparation
of certain sections. The cumbrous seriousness and the dry tone of this
systematic combination o