The mind is out of order, it is incapable of judging sanely--the imagination is badly regulated, whenever man's organization is not so modified, as to perform its functions with precision. At each moment of his existence, man gathers experience; every sensation he has, furnishes a fact that deposits in his brain an idea which his memory recalls with more or less fidelity: these facts connect themselves, these ideas are associated; their chain constitutes _experience_; this lays the foundation of _science_. Knowledge is that consciousness which arises from reiterated experience--from experiments made with precision of the sensations, of the ideas, of the effects which an object is capable of producing, either in ourselves or in others. All science, to be just, must be founded on truth. Truth itself rests on the constant, the faithful relation of our senses. Thus, _truth_ is that conformity, that perpetual affinity, which man's senses, when well constituted, when aided by experience, discover to him, between the objects of which he has a knowledge, and the qualities with which he clothes them. In short, truth is nothing more than the just, the precise association of his ideas. But how can he, without experience, assure himself of the accuracy, of the justness of this association? How, if he does not reiterate this experience, can he compare it? how prove its truth? If his senses are vitiated, how is it possible they can convey to him with precision, the sensations, the facts, with which they store his brain? It is only by multiplied, by diversified, by repeated experience, that he is enabled to rectify the errors of his first conceptions. Man is in error every time his organs, either originally defective in their nature, or vitiated by the durable or transitory modifications which they undergo, render him incapable of judging soundly of objects. Error consists in the false association of ideas, by which qualities are attributed to objects which they do not possess. Man is in error, when he supposes those beings really to have existence, which have no local habitation but in his own imagination: he is in error, when he associates the idea of happiness with objects capable of injuring him, whether immediately or by remote consequences which he cannot foresee.