Towards real progress in knowledge two things are alike indispensable: a true scientific method, and imaginative insight. The former is, in the main, a creation of the modern world, nor was Lucretius here in advance of his age. But in the latter quality he is unsurpassed, if not unequalled. Perhaps this is even clearer in another field of science, that which has within the last generation risen to such immense proportions under the name of anthropology. Thirty years ago it was the first and second books of the _De Rerum Natura_ which excited the greatest enthusiasm in the scientific world. Now that the atomic theory has passed into the rank of received doctrines, the brilliant sketch, given in the fifth book, of the beginnings of life upon the earth, the evolution of man and the progress of human society, is the portion of the poem in which his scientific imagination is displayed most astonishingly. A Roman aristocrat, living among a highly cultivated society, Lucretius had been yet endowed by nature with the primitive instincts of the savage. He sees the ordinary processes of everyday life--weaving, carpentry, metal-working, even such specialised forms of manual art as the polishing of the surface of marble--with the fresh eye of one who sees them all for the first time. Nothing is to him indistinct through familiarity. In virtue of this absolute clearness of vision it costs him no effort to throw himself back into prehistoric conditions and the wild life of the earliest men. Even further than this he can pierce the dim recesses of the past. Before his imagination the earth rises swathed in tropical forests, and all strange forms of life issuing and jostling one another for existence in the steaming warmth of perpetual summer. Among a thousand types that flowered and fell, the feeble form of primitive man is distinguished, without fire, without clothing, without articulate speech. Through the midnight of the woods, shivering at the cries of the stealthy-footed prowlers of the darkness, he crouches huddled in fallen leaves, waiting for the rose of dawn. Little by little the prospect clears round him. The branches of great trees, grinding one against another in the windy forest, break into a strange red flower; he gathers it and hoards it in his cave. There, when wind and rain beat without, the hearth-fire burns through the winter, and round it gathers that other marvellous invention of which the hearth-fire became the mysterious symbol, the family. From this point the race is on the full current of progress, of which the remainder of the book gives an account as essentially true as it is incomparably brilliant. If we consider how little Lucretius had to go upon in this reconstruction of lost history, his imaginative insight seems almost miraculous. Even for the later stages of human progress he had to rely mainly on the eye which saw deep below the surface into the elementary structure of civilisation. There