too, there went on one of a scientific kind, which divided into two
lines, a speculative and a practical. On the former the freelance
philosopher Julien Offray la Mettrie gave a powerful initial push by
his materialistic theses, in which a medical knowledge that for the
time was advanced is applied with a very keen if unsystematic reasoning
faculty to the primary problem of mind and body; and others after
him continued the impulse. La Mettrie produced his Natural History
of the Mind in 1745; [1070] and in 1746 appeared the Essay on the
Origin of Human Knowledge of the Abbé Condillac, both essentially
rationalistic and anti-theological works, though differing in their
psychological positions, Condillac being a non-materialist, though
a strong upholder of "sensism." La Mettrie followed up his doctrine
with the more definitely materialistic but less heedfully planned
works, L'Homme Plante and L'Homme Machine (1748), the second of which,
published at Leyden [1071] and wickedly dedicated to the pious Baron
von Haller, was burned by order of the magistrates, its author being
at the same time expelled from Holland. Both books are remarkable
for their originality of thought, biological and ethical. Though
La Mettrie professed to think the "greatest degree of probability"
was in favour of the existence of a personal God, [1072] his other
writings gave small support to the hypothesis; and even in putting
it he rejects any inference as to worship. And he goes on to quote
very placidly an atheist who insists that only an atheistic world can
attain to happiness. It is notable that he, the typical materialist of
his age, seems to have been one of its kindliest men, by the consent
of all who knew him, [1073] though heedless in his life to the point
of ending it by eating a monstrous meal out of bravado.
The conventional denunciation of La Mettrie (endorsed by Lord
Morley, Voltaire, p. 122) proceeds ostensibly upon those of his
writings in which he discussed sexual questions with absolute
scientific freedom. He, however, insisted that his theoretic
discussion had nothing whatever to do with his practice; and there
is no evidence that he lived otherwise than as most men did in his
age, and ours. Still, the severe censure passed on him by Diderot
(Essai sur les règnes de Claude et de Néron, ed. 1782, ii, 22-24)
seems to convict him of at least levity of character. Voltaire
several times holds the same tone. But Diderot writes so angrily
that his verdict incurs suspicion.
As Lange notes, there has been much loose generalization as to
the place and bearing of La Mettrie in the history of French
thought. Hettner, who apparently had not thought it worth while
to read him, has ascribed his mental movement to the influence
of Diderot's Pensées philosophiques (1746), whereas it had
begun in his own Histoire naturelle de l'âme, published a year
before. La Mettrie's originality and influence in general have been
underestimated as a result of the hostility set up by disparagement
of his character. The idea of a fundamental unity of type in
nature--an idea underlying all the successive steps of Lamarck,
Geoffroy Saint-Hilaire, Goethe, and others, towards the complete
conception of evolution--is set forth by him in L'Homme Plante in
1748, the year in which appeared De Maillet's Telliamed. Buffon
follows in time as in thought, only beginning his great work
in 1749; Maupertuis, with his pseudonymous dissertation on the
Universal system of Nature, applies La Mettrie's conception in
1751; and Diderot's Pensées sur l'interprétation de la nature,
stimulated by Maupertuis, appeared only in 1754. La Mettrie
proceeded from the classification of Linnæus, but did not
there find his idea. In the words of Lange, "these forgotten
writings are in nowise so empty and superficial as is commonly
assumed." Gesch. des Materialismus, i, 328-29. Lange seems to
have been the first to make a judicial study of La Mettrie's work,
as distinguished from the scandals about his character.