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.