I have spoken at considerable length of the skeptics; but I have believed it necessary in explaining a dogmatic work, whose _esprit_ is wholly opposed to that of skepticism. When Lysis wrote in Greece, there had been no one as yet who doubted either the existence of the gods, or that of the Universe, or made the distinction between good and evil, virtue and vice. Arcesilaus and Pyrrho were not born, and the clouds that they raised afterwards concerning these great subjects of the meditation of the sages were not even suspected. The minds had inclined rather toward credulity than toward doubt; toward superstition than toward atheism; it was more necessary to limit their curiosity than to excite their indifference. At that epoch, the philosophers enveloped the truth with veils, and rendered the avenues of science difficult, so that the vulgar might not profane them. They knew what had been too long forgotten: that all kinds of wood are not fitting to make a Mercury. Also their writers were obscure and sententious: in order to dishearten, not those who might be able to doubt, but those who were not in a condition to comprehend. Today, as the minds are changed, it is of more importance to attract those who are able to receive the truth, than to keep at a distance those who are unable to receive it; the latter, separating themselves, are persuaded that they either possess it or have no need of it. I have given the history of skepticism; I have shown its origin and the sorry effects of its absolute and disordered influence; not in order to bring back the skeptics of the profession, but to endeavour to prevent the men who are still drifting in uncertainty from becoming so. I have essayed to show them by the example of one of the greatest reasoners of Germany, by the example of Kant, that reason alone, with whatever talents it may be accompanied, cannot fail to lead them to nothingness. I have made them see that this faculty so lauded is nothing of itself. I am content with the example of the Koenigsberg professor; but had I not feared prolixities, I would have added the example of Berkeley and that of Spinoza. The varied catastrophes of these three savants form a striking contrast. Kant, following step by step his pure Reason, comes to see that the knowledge of intelligible things is impossible and finds matter; Berkeley, led by the same reason, proves that the existence of matter is illusory, and that all is spirit; Spinoza, drawing irresistible arguments from this same faculty, shows that there exists and can exist only one sole substance and that therefore spirit and matter are but one. And do not think that, armed with reason alone, you can combat separately Spinoza, Berkeley, or Kant: their contradictory systems will clash in vain; they will triumph over you and will push you into the dark and bottomless abyss of skepticism.