In all the phenomena man presents, from the moment he quits the womb of his mother, to that wherein he becomes the inhabitant of the silent tomb, he perceives nothing but a succession of necessary causes and effects, which are strictly conformable to those laws that are common to all the beings in Nature. All his modes of action--all his sensations--all his ideas--all his passions--every act of his will--every impulse which he either gives or receives, are the necessary consequences of his own peculiar properties, and those which he finds in the various beings by whom he is moved. Every thing he does--every thing that passes within himself--his concealed motion--his visible action, are the effects of inert force--of self-gravitation--the attractive or repulsive powers contained in his machine--of the tendency he has, in common with other beings, to his own individual preservation; in short, of that energy which is the common property of every being he beholds. Nature, in man, does nothing more than shew, in a decided manner, what belongs to the peculiar nature by which he is distinguished from the beings of a different system or order.
The source of those errors into which man has fallen, when he has contemplated himself, has its rise, as will presently be shown, in the opinion he has entertained, that he moved by himself--that he always acts by his own natural energy--that in his actions, in the will that gave him impulse, he was independent of the general laws of Nature; and of those objects which, frequently, without his knowledge, always in spite of him, in obedience to these laws, are continually acting upon him. If he had examined himself attentively, he must have acknowledged, that none of the motion he underwent was spontaneous--he must have discovered, that even his birth depended on causes, wholly out of the reach of his own powers--that, it was without his own consent he entered into the system in which he occupies a place--that, from the moment in which he is born, until that in which he dies, he is continually impelled by causes, which, in spite of himself, influence his frame, modify his existence, dispose of his conduct. Would not the slightest reflection have sufficed to prove to him, that the fluids, the solids, of which his body is composed, as well as that concealed mechanism, which he believes to be independent of exterior causes, are, in fact, perpetually under the influence of these causes; that without them he finds himself in a total incapacity to act? Would he not have seen, that his temperament, his constitution, did in no wise depend on himself--that his passions are the necessary consequence of this temperament--that his will is influenced, his actions determined by these passions; consequently by opinions, which he has not given to himself, of which he is not the master? His blood, more or less heated or abundant; his nerves more or less braced, his fibres more or less relaxed, give him dispositions either transitory or durable--are not these, at every moment decisive of his ideas; of his thoughts: of his desires: of his fears: of his motion, whether visible or concealed? The state in which he finds himself, does it not necessarily depend on the air which surrounds him diversely modified; on the various properties of the aliments which nourish him; on the secret combinations that form themselves in his machine, which either preserve its order, or throw it into confusion? In short, had man fairly studied himself, every thing must have convinced him, that in every moment of his duration, he was nothing more than a passive instrument in the hands of necessity.