and comparative methods enabled Montesquieu to criticize the existing social conditions incisively and systematically. His over-rapid generalizations however are unhistorical. He proposes an ideal form of the English constitution, without observing that the long period of the political development of the English people by means of self- government in smaller groups was its historical presupposition.
Condillac (1715-1780) attempted a simplification of Locke's theory of knowledge in his Traité des sensations (1754), by means of referring the whole of our conscious experience to absolutely passive sensations. Attention is nothing more than an intense sensation, which precludes the possibility of another sensation arising; memory is simply a secondary effect of sensation, and comparison consists of nothing more than the concomitant appearance of two sensations. The comparison of pleasure and pain gives rise to desires and impulses.—Notwithstanding his endeavor to eliminate every form of activity from psychology, Condillac still adheres to the Cartesian theory of the soul and the body as two distinct entities. Sensation cannot be identified with motion, and our ability to make comparisons (i. e., to be conscious of two sensations at the same moment) definitely proves that the vehicle of sensations is a simple substance. Condillac, who was a Catholic ecclesiastic, was thus able to harmonize his psychology with his theology. But the spiritualistic element of Condillac's theory was devoid of influence. His followers insisted on reducing all psychical phenomena to passive sensations.
La Mettrie (1702-1751), a physician, had even before this time substituted a thorough-going materialism for the Cartesian dualism in his famous work, L'homme machine
