features it is superior to any other physical theory of the universe
which existed up to the seventeenth century. In his theory of light
Lucretius was in advance of Newton. In his theory of chemical affinities
(for he describes the thing though the nomenclature was unknown to him)
he was in advance of Lavoisier. In his theory of the ultimate
constitution of the atom he is in striking agreement with the views of
the ablest living physicists. The essential function of science--to
reduce apparently disparate phenomena to the expressions of a single law
--is not with him the object of a moment's doubt or uncertainty.

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