IN 1748 Albrecht von Haller, the Swiss physiologist and physician, found himself the unwilling recipient of the dedication of an anonymous pamphlet entitled "L'homme machine."1 Nothing could have been more at variance with his pious philosophy, and the controversies aroused by its theme burned with a white heat.
The message carried by this pamphlet, which was almost certainly written by the French physician, La Mettrie, was that man's sole guide to the universe is the observations he makes and that preconceived deductions are valueless. Nearly two centuries later Einstein gives us the same warning against metaphysics: "In order that thinking might not degenerate into 'metaphysics' or into empty talk, it is only necessary that enough propositions of the conceptual system be firmly enough connected with sensory experiences."
The author of "L'homme machine" expresses himself in terms which for his century are strongly neurophysiological. The "faculties of the soul" are