Diderot is always ready to fling away his proper subject in a burst of moralising. The article on _Man_, as a branch of natural history, contains a correct if a rather superficial account of that curious animal; at length the writer comes to a table showing the probable duration of life at certain ages. "You will observe," he says, "1st, that the age of seven is that at which you may hope a longer life; 2d, that at twelve or thirteen you have lived a quarter of your life; at twenty-eight or twenty-nine you have lived half; at fifty more than three-quarters." And then he suddenly winds up the whole performance by the exclamation: "O ye who have laboured up to fifty, who are in the enjoyment of comfort, and who still have left to you health and strength, what then are you waiting for before you take rest? How long will you go on saying _To-morrow, to-morrow?_"
There are many casual brilliancies in the way of analogy and parallel, many aptnesses of thought and phrase. The Stoics are called the Jansenists of Paganism. "For a single blade of grass to grow, it is necessary that the whole of nature should co-operate." "A man comes to Pyrrhonism by one of two opposite ways; either because he does not know enough, or because he knows too much; the latter is not the most common way." And so forth.
If we turn to the group of articles dealing with theology, it is difficult for us to know exactly where we are. Sometimes Diderot writes of popular superstitions with the gravity proper to a dictionary of mythology. Sometimes he sews on to the sober gray of his scepticism a purple patch of theistic declamation.[178] The article on Jesus Christ is obviously a mere piece of common form, and more than one passage in his article on _Christianisme_ is undoubtedly insincere. When we come to his more careful article, _Providence_, we find it impossible to extract from it a body of coherent propositions of which we could confidently say that they represented his own creed, or the creed that he desired his readers to bear away in their minds.
It is hardly worth while to measure the more or the less of his adherence to Christianity, or even to Deism, as inferred from the Encyclopædia. We need only turn to his private letters to find that he is in no degree nor kind an adherent, but the most hardy, contemptuous, and thoroughgoing of opponents. At the risk of shocking devout persons, I am bound to reproduce a passage from one of his letters, in which there can be no doubt that we have Diderot's true mind, as distinguished from what it was convenient to print. "The Christian religion," he says, "is to my mind the most absurd and atrocious in its dogmas; the most unintelligible, the most metaphysical, the most intertwisted and obscure, and consequently the most subject to divisions, sects, schisms, heresies; the most mischievous for the public tranquillity, the most dangerous to sovereigns by its hierarchic order, its persecutions, its discipline; the most flat, the most dreary, the most Gothic, and the most gloomy in its ceremonies; the most puerile and unsociable in its morality, considered not in what is common to it with universal morality, but in what is peculiarly its own, and constitutes it evangelical, apostolical, and Christian morality, which is the most intolerant of all. Lutheranism, freed from some absurdities, is preferable to Catholicism; Protestantism to Lutheranism, Socinianism to Protestantism, Deism, with temples and ceremonies, to Socinianism. Since it is necessary that man, being superstitious by nature, should have a fetish, the simplest and most harmless will be the best fetish."[179] We need not discuss nor extend the quotation; enough has been said to relieve us from the duty of analysing or criticising articles in which Christianity is treated with all the formal respect that the secular authority insisted upon.