In this rudimentary form the chief speaker presses some of the objections to optimistic deism from the point of view of the fixed limitations, the inevitable relativity, of human knowledge.  This kind of objection had been more pithily expressed by Pascal long before, in the famous article of his Thoughts, on the difficulty of demonstrating the existence of a deity by light of nature.[50] Diderot’s argument does not extend to dogmatic denial.  It only shows that the deist is exposed to an attack from the same sceptical armoury from which he had drawn his own weapons for attacking revelation.  It is impossible to tell how far Diderot went at this moment.  The trenchancy with which his atheist urges his reasoning, proves that the writer was fully alive to its force.  On the other hand, the atheist is left in the midst of a catastrophe.  On his return home, he finds his children murdered, his house pillaged, and his wife carried off.  And we are told that he could not complain on his own principles.

If the absence of witnesses allowed the robber to commit his crime with impunity, why should he not?  Again, there is a passage in which the writer seems to be speaking his own opinions.  An interlocutor maintains the importance of keeping the people in bondage to certain prejudices.  “What prejudices?  If a man once admits the existence of a God, the reality of moral good and evil, the immortality of the soul, future rewards and punishments, what need has he of prejudices?  Supposing him initiated in all the mysteries of transubstantiation, consubstantiation, the Trinity, hypostatical union, predestination, incarnation, and the rest, will he be any the better citizen?"[51]

In truth, Diderot’s mind was at this time floating in an atmosphere of rationalistic negation, and the moral of his piece, as he hints, points first to the extravagance of Catholicism, next to the vanity of the pleasures of the world, and lastly, to the unfathomable uncertainty of philosophy.  Still, we may discern a significant leaning towards the theory of the eternity of matter, which has arranged itself and assumed variety of form by virtue of its inherent quality of motion.[52]

It is a characteristic and displeasing mark of the time that Diderot in the midst of these serious speculations, should have set himself (1748) to the composition of a story in the kind which the author of the Sofa had made highly popular.  The mechanism of this deplorable piece is more grossly disgusting—­I mean aesthetically, not morally—­than anything to be found elsewhere in the too voluminous library of impure literature.  The idea would seem to have been borrowed from one of the old Fabliaux.[53] But what is tolerable in the quaint and naif verse of the twelfth or thirteenth century, becomes shocking when deliberately rendered by a grave man into bald unblushing prose of the eighteenth.  The humour, the rich sparkle, the wit, the merry gaillardise,