The Pensées Philosophiques were an early work of Diderot’s written around 1747. They were popular but also got him into trouble by critiquing religious belief and Catholicism. A few years later he would be an outright atheist. They are more aphoristic than usual; he was never given to great exegesis, but he tended to avoid the overly polemical statement as well. Chalk it up to youth. The translation here is from 1916, by Margaret Jourdain, and is a bit antiquated. I’m not aware of a newer one.

People are for ever declaiming against the passions; they attribute to them all the pains that man endures, and forget that they are also the source of all his pleasures. It is an ingredient in man’s constitution which cannot sufficiently be blessed and banned. It is considered as an affront to reason if one ventures to say a word in favour of its rivals; yet it is passions alone, and strong passions, that can elevate the soul to great things. Without them, there is no sublime, either in morality or in achievement; the fine arts return to puerility, and virtue becomes a pettifogging thing.

It is not from the metaphysician that atheism has received its most vital attack. The sublime meditations of Malebranche and Descartes were less calculated to shake materialism than a single observation of Malpighi’s. If this dangerous hypothesis is tottering at the present day, it is to experimental physics that the result is due. It is only in the works of Newton, of Muschenbroek, of Hartzoeker, and of Nieuwentit, that satisfactory proofs have been found of the existence of a reign of sovereign intelligence. Thanks to the works of these great men, the world is no longer a God; it is a machine with its wheels, its cords, its pulleys, its springs, and its weights.

You grant me that matter exists from all eternity and that movement is essential to it. In return for this concession, I will suppose, as you do, that the world has no limits, that the multitude of atoms is infinite, and that this order which causes you astonishment nowhere contradicts itself. Well, from these mutual admissions there follows nothing else unless it be that the possibility of fortuitously creating the universe is very small but that the quantity of throws is infinite; that is to say, that the difficulty of the result is more than sufficiently compensated by the multitude of throws. Therefore, if anything ought to be repugnant to reason, it is the supposition that –matter being in motion from all eternity, and there being perhaps in the infinite number of possible combinations an infinite number of admirable arrangements,–none of these admirable arrangements would have ensued, out of the infinite multitude of those which matter took on successively. Therefore the mind ought to be more astonished at the hypothetical duration of chaos than at the actual birth of the universe.

And a note on style, from “Letter on the Deaf-Mutes”:

The poet and the orator gain by studying harmony of style, and the musician finds his compositions are improved by avoiding certain chords and certain intervals, and I praise their efforts; but at the same time I blame that affected refinement which banishes from our language a number of vigorous expressions. The Greeks and Romans were strangers to this false refinement, and said what they liked in their own language, and said it as they liked. By overrefining we have impoverished our language; and though there may be only one term which expresses an idea, we prefer rather to weaken the idea than to express it by some vulgar word or expression. How many words are thus lost to our great imaginative writers, words which we find with pleasure in the pages of Amyot and Montaigne! They were at first rejected from a refined style, because they were commonly used by the people; later on they were rejected by the common people, who always ape their betters, and they are become entirely obsolete. I believe we shall soon become like the Chinese, and have a different written and spoken language.

I have a great affection for Diderot and see him embodying most of the Enlightenment’s virtues (tolerance, curiosity, skepticism, logical thought, creative intuition) and few of its vices (overreaching, overgeneralization, arrogance, optimism, cynicism). This little portrait of him by the French Radical-Socialist Prime Minister Edouard Herriot (a flawed but still sympathetic figure in his own right), written in 1953, captures a great deal of his charm, though I think it’s on display in nearly everything he wrote.

I remember how in 1913 the French Senate wished to celebrate the second centenary of Diderot’s birth. I was then a member, the youngest, of that assembly. I said a few words which met with very little response. The Chamber did not support the suggestion that his remains should be moved to the Panthéon, and Maurice Barrès expressed his satisfaction at this in a careful essay which appeared in his book Les Maîtres. He did not consider Diderot to be a national figure; he saw him merely as a remarkable revolutionary genius, able as no one else to place charges of dynamite under all the principles and pillars on which society rests; a professor, as it were, of anarchy and an enemy of tradition.

Diderot considered a humanist education to be essential. ‘For several years running,’ he writes in his Project for a University, ‘I would read a passage of Homer every night before going to bed as regularly as a good priest says his office. I began early to suck the milk of Homer, Virgil, Horace, Terence, Anacreon, Plato, and Euripides, mixed with that of Moses and the Prophets.’

As a matter of fact he wanted to study everything and to know everything. As soon as he left college his true nature became apparent. Unable to settle down in an attorney’s office, refusing to choose a definite profession, flitting from literature to science and from Italian to English, mixing with company of every description both good and bad, but more often the latter, composing sermons, if necessary, for a Portuguese missionary, tutoring the children of Randon d’Haunecourt, the financier, but throwing up his job in order to be free again, sometimes reduced even to hunger, he managed to gain through his very independence a wide experience and culture which made him a singularly intelligent and well-informed Bohemian. At one moment we see him dressed in a grey plush coat taking a summer stroll along the Allée des Soupirs in the Luxembourg Gardens, and, at the next, wandering through the streets of Paris with torn cuffs and black woollen stockings sewn together at the back with white thread.

His originality lies primarily in his vast culture and in his scientific knowledge, so far in advance of that of his contemporaries. He had already reached an idea of transformism, the doctrine of evolution. A materialist, in favour of morality for sentimental and practical reasons, not from philosophic conviction, laudably hard-working, curious about everything, often confused, even incoherent but generous, cordial, with a shade of coarseness, becoming intoxicated with ideas, as others do with wine, vulgar at times and disordered as he was said to be, outstanding quality was life.