Diderot's knowledge of our language now did him good service. One of the details of the method by which he taught himself English is curious. Instead of using an Anglo-French dictionary, he always used one in Anglo-Latin. The sense of a Latin or Greek word, he said, is better established, more surely fixed, more definite, less liable to capricious peculiarities of convention, than the vernacular words which the whim or ignorance of the lexicographer may choose. The reader composes his own vocabulary, and gains both correctness and energy.[25] However this may be, his knowledge of English was more accurate than is possessed by most French writers of our own day. Diderot's first work for the booksellers after his marriage seems to have been a translation in three volumes of Stanyan's History of Greece. For this, to the amazement of his wife, he got a hundred crowns. About the same time (1745) he published Principles of Moral Philosophy, or an Essay of Mr. S. on Merit and Virtue. The initial stands for Shaftesbury, and the book translated was his Inquiry concerning Virtue and Merit.
Towards the same time, again, Diderot probably made acquaintance with Madame de Puisieux, of whom it has been said with too patent humour that she was without either the virtue or the merit on which her admirer had just been declaiming. We are told that it was her need of money which inspired him with his first original work. As his daughter's memoir, from which the tale comes, is swarming with blunders, this may not be more true than some of her other statements. All that we know of Diderot's sense and sincerity entitles him to the benefit of the doubt. The Philosophical Thoughts (1746) are a continuation of the vein of the annotations on the Essay. He is said to have thrown these reflections together between Good Friday and Easter Sunday. Nor is there anything incredible in such rapid production, when we remember the sweeping impetuosity with which he flung himself into all that he undertook. The Thoughts are evidently the fruits of long meditation, and the literary arrangement of them may well have been an easy task. They are a robuster development of the scepticism which was the less important side of Shaftesbury. The parliament of Paris ordered the book to be burnt along with some others (July 7, 1746), partly because they were heterodox, partly because the practice of publishing books without official leave was gaining an unprecedented height of license.[26] This was Diderot's first experience of that hand of authority, which was for thirty years to surround him with mortification and torment. But the disapproval of authority did not check the circulation or influence of the Thoughts. They were translated into German and Italian, and were honoured by a shower of hostile criticism. In France they were often reprinted, and even in our own day they are said not wholly to have lost their vogue as a short manual of scepticism.[27]