While self-government lasted, rationalism among the cultured classes was fairly common. The great poem of Lucretius, On the Nature of Things, with its enthusiastic exposition of the doctrine of Epicurus, remains to show to what a height of sincerity and ardour a Roman freethinker could rise. No Greek utterance that has come down to us makes so direct and forceful an attack as his on religion as a social institution. He is practically the first systematic freethinking propagandist; so full is he of his purpose that after his stately prologue to alma Venus, who is for him but a personification of the genetic forces of Nature, he plunges straight into his impeachment of religion as a foul tyranny from which thinking men were first freed by Epicurus. The sonorous verse vibrates with an indignation such as Shelley's in Queen Mab: religion is figured as horribili super aspectu mortalibus instans; a little further on its deeds are denounced as scelerosa atque impia, "wicked and impious," the religious term being thus turned against itself; and a moving picture of the sacrifice of Iphigeneia justifies the whole. "To so much of evil could religion persuade." It is with a bitter consciousness of the fatal hold of the hated thing on most men's ignorant imagination that he goes on to speak of the fears [781] so assiduously wrought upon by the vates, and to set up with strenuous speed the vividly-imagined system of Epicurean science by which he seeks to fortify his friend against them. That no thing comes from nothing, or lapses into nothing; that matter is eternal; that all things proceed "without the Gods" by unchanging law, are his insistent themes; and for nigh two thousand years a religious world has listened with a reluctant respect. His influence is admitted to have been higher and nobler than that of the religion he assailed. "Lucretius was the first not only to reveal a new power, beauty, and mystery in the world, but also to communicate to poetry a speculative impulse, opening up, with a more impassioned appeal than philosophy can do, the great questions underlying human life--such as the truth of all religious tradition, the position of man in the universe, and the attitude of mind and course of conduct demanded by that position." (Sellar, Roman Poets of the Republic: Virgil, 1877, p. 199.) "In the eyes of Lucretius all worship seemed prompted by fear and based on ignorance of natural law.... But it is nevertheless true that Lucretius was a great religious poet. He was a prophet, in deadly earnest, calling men to renounce their errors both of thought and conduct.... We may be certain that he was absolutely convinced of the truth of all that he wrote." (W. Warde Fowler, Social Life at Rome in the Age of Cicero, 1909, pp. 327-28.)