One of the finest products of the Greco-Roman imagination is the fifth book of Lucretius' poem De rerum natura. In magnificent language the Latin poet pictures the successive stages of the evolution of the cosmos from clouds of atomic dust, and with great intensity displays the explanatory advantages of his materialism over the cosmic gods of ancient mythology and rival philosophies. First comes the framework of the cosmos: earth and sun, the stars, planets, sun and moon, and the seasons of the earth. Then the poem goes on to tell of the first growth of vegetation, the emergence of animal life, the earliest human communities, the growth of civilization and technology, the development of political structures, and the genealogy of morals.

There can be little doubt that the Atomists of the fifth century b.c. wrote about these things too, and that many of their ideas were adopted by Epicurus and his Greek followers, who were themselves the sources of Lucretius' inspiration. It happens that Lucretius' poem has survived intact, while the work of Leucippus and Democritus has vanished. The fifth book of De rerum natura, then, is our best source for this aspect of ancient Atomism. Nevertheless, it seems appropriate to study Lucretius in his Epicurean context, rather than as an appendix to Democritus. Although there is in all probability much in Lucretius book v that comes from Democritus, there is certainly much that does not. So at the cost of leaving our history of Preplatonic Atomism embarrassingly threadbare in this area, we shall not draw on Lucretius' anthropology for evidence here, and postpone the attempt to give a more satisfactory account of the atomic theory to volume 2.