I shall venture to quote a hardy passage from another article (Pyrrhonienne) which some will think a measure of Diderot’s philosophical incompetency, and others will think a measure of his good sense.  “We will conclude,” he says, “for our part that as all in nature is bound together, there is nothing, properly speaking, of which man has perfect, absolute, and complete knowledge, because for that he would need knowledge of all.  Now as all is bound together, it inevitably happens that, from discussion to discussion, he must come to something unknown:  then in starting again from this unknown point, we shall be justified in pleading against him the ignorance or the obscurity or the uncertainty of the point preceding, and of that preceding this, and so forth, up to the most evident principle.  So we must admit a sort of sobriety in the use of reason.  When step by step I have brought a man to some evident proposition, I shall cease to dispute.  I will listen no longer to a man who goes on to deny the existence of bodies, the rules of logic, the testimony of the senses, the difference between good and evil, true and false, etc. etc.  I will turn my back on everybody who tries to lead me away from a simple question, to embark me in discussion as to the nature of matter, of the understanding of thought, and other subjects shoreless and bottomless."[185] Whatever else may be said of this, we have to recognise that it is exactly characteristic of the author.  But then why have written on metaphysics at all?

We have mentioned the article on Spinosa.  It is characteristic both of the good and the bad sides of Diderot’s work.  Half of it is merely a reproduction of Bayle’s criticisms on Spinosa and his system.  The other half consists of original objections propounded by Diderot with marked vigour of thrust against Spinosa, but there is no evidence that he had gone deeper into Spinosa than the first book of the Ethics.  There is no certain sign that he had read anything else, or that he had more of that before him than the extracts that were furnished by Bayle.  Such treatment of a serious subject hardly conforms to the modern requirements of the literary conscience, for in truth the literary conscience has now turned specialist and shrinks from the encyclopaedic.  Diderot’s objections are, as we have said, pushed with marked energy of speech.  “However short away,” he says, “you penetrate into the thick darkness in which Spinosa has wrapped himself up, you discover a succession of abysses into which this audacious reasoner has precipitated himself, of propositions either evidently false or evidently doubtful, of arbitrary principles, substituted for natural principles and sensible truths; an abuse of terms taken for the most part in a wrong sense, a mass of deceptive equivocations, a cloud of palpable contradictions.”  The system is monstrous, it is absurd and ridiculous.  It is Spinosa’s plausible method that has deceived people; they supposed that one who employed geometry, and proceeded by way of axioms and definitions, must be on the track of truth.  They did not see that these axioms were nothing better than very vague and very uncertain propositions; that the definitions were inexact, defective, and bizarre.