In about 1735, Emilie Du Châtelet began to translate Mandeville's Fable of the Bees. Her work, which is largely ignored by scholars, did, as this article demonstrates, turn out to be one of transformation rather than of translation and came at a crucial moment in the emerging French luxury debate. So far commercial society and luxury had been defended in purely economic terms, for instance in Melon's Essai politique, or as an aspect of divine providence for fallen man, by Pierre Nicole amongst others. There was as yet no coherent defence on the level of secular ethics. As this article shows, Du Châtelet set out to remedy this. In co-operation with Voltaire, with whose recent praise of English society in the Lettres philosophiques she strongly identified, she rewrote the Fable to offer a defence of modern commercial society as both natural and moral. The article argues that she was able to do so by taking recourse to classic Epicureanism in the guise of Lucretius' De rerum natura, as an alternative to the Neo-Epicureanism, with its Augustinian overtones, as espoused by Mandeville. Voltaire in turn used her translation to lay the foundations for his defence of commercial society and progress in his Traité de métaphysique in which he uses the precise passages she had inserted into Mandeville's original. This article analyses the further aspects Voltaire adds to her arguments. Taken together, Du Châtelet's ‘translation’ and Voltaire's Traité offer a coherent defence of bourgeois society that would underlie Voltaire's later historiographical and philosophical works and which were crucial to his concept of ‘Enlightenment’ and ‘progress’.