To our own age the Epicurean philosophy has a double interest. Not only was it a philosophy of life and conduct, but, in the effort to place life and conduct under ascertainable physical laws, it was led to frame an extremely detailed and ingenious body of natural philosophy, which, partly from being based on really sound postulates, partly from a happy instinct in connecting phenomena, still remains interesting and valuable. To the Epicureans, indeed, as to all ancient thinkers, the scientific method as it is now understood was unknown; and a series of unverified generalizations, however brilliant and acute, is not the true way towards knowledge. But it still remains an astonishing fact that many of the most important physical discoveries of modern times are hinted at or even expressly stated by Lucretius. The general outlines of the atomic doctrine have long been accepted as in the main true; in all important 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.