Whenever our will is moved by concealed and complicated motives, it is extremely difficult to decide what determines it; a wicked man may be conducted to incredulity or to scepticism by those motives which he dare not avow, even to himself; in believing he seeks after truth, he may form an illusion to his mind, only to follow the interest of his passions; the fear of an avenging system will perhaps determine him to deny their existence without examination; uniformly because he feels them incommodious. Nevertheless, the passions sometimes happen to be just; a great interest carries us on to examine things more minutely; it may frequently make a discovery of the truth, even to him who seeks after it the least, or who is only desirous to be lulled to sleep, who is only solicitous to deceive himself. It is the same with a perverse man who stumbles upon truth, as it is with him, who flying from an imaginary danger, should encounter in his road a dangerous serpent, which in his haste he should destroy; he does that by accident, without design, which a man, less disturbed in his mind, would have done with premeditated deliberation.
To judge properly of things, it is necessary to be disinterested; it is requisite to have an enlightened mind, to have connected ideas to compass a great system. It belongs, in fact, only to the honest man to examine the proofs of systems--to scrutinize the principles of superstition; it belongs only to the man acquainted with nature, conversant with her ways, to embrace with intelligence the cause of the SYSTEM OF NATURE. The wicked are incapable of judging with temper; the ignorant are inadequate to reason with accuracy; the honest, the virtuous, are alone competent judges in so weighty an affair. What do I say? Is not the virtuous man, from thence in a condition to ardently desire the existence of a system that remunerates the goodness of men? If he renounces those advantages, which his virtue confers upon him the right to hope, it is, undoubtedly, because he finds them imaginary. Indeed, every man who reflects will quickly perceive, that for one timid mortal, of whom these systems restrain the feeble passions, there are millions whose voice they cannot curb, of whom, on the contrary, they excite the fury; for one that they console, there are millions whom they affright, whom they afflict; whom they make unhappy: in short, he finds, that against one inconsistent enthusiast, which these systems, which are thought so excellent, render happy, they carry discord, carnage, wretchedness into vast countries; plunge whole nations into misery; deluge them with tears.