If the source be traced of that profound ignorance in which man is with respect to his morals, to the motives that can give volition to his will, it will be found in those false ideas which the greater number of speculators have formed to themselves, of human nature. The science of morals has become an enigma which it is impossible to unrevel; because man has made himself double; has distinguished his soul from his body; supposed it of a nature different from all known beings, with modes of action, with properties distinct from all other bodies, because he has emancipated this soul from physical laws, in order to submit it to capricious laws emanating from men who have pretended they are derived from imaginary regions, placed at very remote distances: metaphysicians seized upon these gratuitous suppositions, and by dint of subtilizing them, have rendered them completely unintelligible. These moralists have not perceived that motion is essential to the soul as well as to the living body; that both the one and the other are never moved but by material, by physical objects; that the want of each regenerate themselves unceasingly; that the wants of the soul, as well as those of the body are purely physical; that the most intimate, the most constant connection subsists between the soul and the body; or rather they have been unwilling to allow that they ate only the same thing considered under different points of view. Obstinate in their supernatural, unintelligible opinions, they have refused to open their eyes, which would have convinced them that the body in suffering rendered the soul miserable; that the soul afflicted undermined the body and brought it to decay; that both the pleasures and agonies of the mind have an influence over the body, either plunge it into sloth or give it activity: they have rather chosen to believe, that the soul draws its thoughts, whether pleasant or gloomy, from its own peculiar sources, while the fact is, that it derives its ideas only from material objects that strike on the physical organs; that it is neither determined to gaiety nor led on to sorrow, but by the actual state, whether permanent or transitory, in which the fluids and solids of the body are found. In short, they have been loath to acknowledge that the soul, purely passive, undergoes the same changes which the body experiences; is only moved by its intervention; acts only by its assistance, receives its sensations, its perceptions, forms its ideas, derives either its happiness or its misery from physical objects, through the medium of the organs of which the body is composed; frequently without its own cognizance, often in despite of itself.