Superficial readers are ignorant of the mental ferment which went on in France before the Revolution. Voltaire's policy of sapping the dogmas by which all tyranny was supported had been carried out unflinchingly. Not only had Christianity been attacked in every conceivable way, with science, scholarship, argument, and wit; but the very foundations of all religion--the belief in soul and God--had not been spared. The Heresiarch of Ferney lived to see the war with superstition carried farther than he contemplated or desired; but it was impossible for him to say to the tide of Freethought, "Thus far shalt thou go and no farther, and here shall thy proud waves be stayed." The tide poured on over everything sacred. Altars, thrones, and coronets met with a common fate. True, they were afterwards fished out of the deluge; but their glory was for ever quenched, their power for ever gone. Among the great Atheists who prepared the Revolution we single out two--Diderot and D'Holbach. The sagacious mind of Comte perceived that Diderot was the greatest _thinker_ of the band. The fecundity of his mind was extraordinary, and even more so his scientific prescience. Anyone who looks through the twenty volumes of his collected works will be astonished at the way in which, by intuitive insight, he anticipated so many of the best ideas of Evolution. His labors on the Encyclopaedia would have tired out the energies of twenty smaller men, but he persevered to the end, despite printers, priests, and governments, and a countless host of other obstructions. Out of date as the work is now, it was the artillery of the movement of progress then. As Mr. Morley says, it "rallied all that was best in France round the standard of light and social hope." Less original, but nearly as bold and industrious, D'Holbach placed his fortune and abilities at the service of Freethought. Mr. Morley calls the _System of Nature_ "a thunderous engine of revolt." It was Atheistic in religion, and revolutionary in politics. It challenged every enemy of freedom in the name of reason and humanity. Here and there its somewhat diffuse rhetoric was lit up with the splendidly concise eloquence of Diderot, who touched the work with a master-hand. Nor did this powerful book represent a tithe of D'Holbach's labors for the "good old cause." His active pen produced a score of other works, under various names and disguises, all addressed to the same object--the destruction of superstition and the emancipation of the human mind. They were extensively circulated, and must have created a powerful impression on the reading public.