He imposes on himself a far graver task. After a pathetic recital of the sacrifice of Iphigenia on the altar of religion by the hand of her father, Lucretius writes the great line of the poem—
Tantum religio potuit suadere malorum—
such are the evils to which religion leads! And he soon adds, "This terror and darkness of mind must be dispelled, not by the rays of the sun and the glittering shafts of day, but by the aspect and law of nature." His lofty aim is no less than the permanent defeat of the ancient reign of superstition by setting forth the new knowledge of nature.
The poem is in six books, which aggregate nearly seven and a half thousand lines. It is not far from three-fourths the length of 'Paradise Lost.' In the first book Lucretius expounds the physics of his great master Epicurus, starting with the fundamental principle that nothing comes from nothing, and the other that all that is is either atoms or space. In the second book he derives all the properties of things from the shapes and concourse of the atoms. The remaining books apply the general principles of the first two to sensation and the doctrine of the soul's immortality, the origin and the final ruin of the mass and fabric of the world, the origin of plants and animals, the rise and development of human civilization, and lastly the explanation of certain terrifying phases of nature, as thunder, earthquake, volcanic eruptions and the plague.
If it be asked, How can this exposition of ancient physics, biology and physical geography be poetry? it must be answered that much of it is not poetry. But the same is true of 'Paradise Lost' or 'The Ring and the Book.' A poem is to be judged, not by the proportion of prosaic content which it carries, nor by successes or infelicities of detail, but by the single impression which it makes considered in its totality. Judged by this standard the poem of Lucretius is one of the world's masterpieces. It becomes all the more remarkable when we recall the limitations under which the poet worked: the language in which he wrote had hitherto been all unused to the music of verse, the exigencies of the exposition of an obscure and prosaic subject-matter dominated the treatment, and the yoke of a practical moral purpose was always on the neck of the poetic impulse.
Of course the value of Lucretius does not lie in his science, and yet our subject demands some consideration of at least one feature of his scientific system. In the first place, he has, amid many puerilities, some curious foreshadowings of modern scientific opinion. The following may be cited: the eternity of matter;"[1] the conservation of matter[2] and of force[3]—Haeckel's 'law of substance'; the atomic con-
