It purported to be by a person called Boulanger. It asserted Christianity to be unnecessary for the maintenance of law and order; declared its dogmas incoherent, its morals fit only to make enthusiasts and fanatics, and its political results infinitely fatal and disastrous. Voltaire fell upon the thing tooth and nail. ‘Impiety Unveiled,’ he called it. It was not Christianity, but the perversions of Christianity, with which _he_ quarrelled. In the margin of his own copy of the book he wrote criticisms as scathing as they are brief. That it was both discussed and condemned at d’Holbach’s table, is practically certain. Galiani at least professed Christianity; Turgot practised it. There are many men--there were some even round d’Holbach’s board--who, having themselves relinquished a faith, are yet greatly averse to hearing that faith blasphemed; and who would fain leave for the souls of others the consolations their reason denies to their own. D’Holbach, to be sure, would commend the thing. ‘A proselytising atheist,’ as his friends had long known him to be--he _must_ approve this daring effort to make men think as he did. Soon came talk of other books--from the same hand it might be--certainly from a hand as bold. In 1767 appeared a pamphlet called ‘The Mind of the Clergy;’ in 1768 ‘Priests Unmasked,’ and ‘Portable Theology.’ The last was condemned to be burnt. Then came whispers of yet another work on the same lines, but on a far larger scale, written with an even greater daring, with ‘the zeal of a missionary for atheism,’ with a passion, a fanaticism, an enthusiasm, usually associated with the ‘heated pulpiteer’ of some narrow sect; and yet having in it, too, something of the serenity, the calm and confident faith of the believer wholly satisfied with his belief. Who has written it? A. M. Mirabaud, Perpetual Secretary to the French Academy, is to be the name, it is said, on the title-page. But the real author? Diderot, whose Encyclopædic labours bring him in touch with all the literary men in Paris, is impulsively positive that he has not the slightest idea. Naigeon--Naigeon, the Baron’s factotum--is abroad on some business of the Baron’s and cannot be appealed to. Most of the company condemn the book unseen. The extremists of the party are always the worst enemies the party has to dread. At the head of his table, fingering his glass thoughtfully, the Baron, with his benevolent, leisurely air, is only following his usual custom in saying little and listening much. In August 1770, there was published in London and Amsterdam ‘The System of Nature, or The Laws of the Physical and Moral World,’ by Mirabaud, Perpetual Secretary to the French Academy. The best kept literary secret in history is the authorship of the ‘Letters of Junius,’ for that remains a secret still. But the Baron d’Holbach’s authorship of ‘The System of Nature’ is certainly among the most piquant concealments in literature.