cautious to confuse the metaphysical materialism with which he was concerned, with historical materialism which has no essential connection with it, and is merely a _way of speaking_. But the metaphysical materialism of the authors of the new historical doctrine, and the name given to the latter, have been not a little misleading. I will refer as an example to a recent and bad little book, which seems to me symptomatic, by a sufficiently accredited socialist writer, Plechanow.[4] The author, designing to study historical materialism, thinks it needful to go back to Holbach and Helvetius. And he waxes indignant at metaphysical dualism and pluralism, declaring that 'the most important philosophical systems were always _monistic_, that is they interpreted matter and spirit as merely two classes of phenomena having a single and indivisible cause.' And in reference to those who maintain the distinction between the factors in history, he exclaims: 'We see here the old story, always recurring, of the struggle between eclecticism and monism, the story of the dividing walls; here nature, there spirit, etc.' Many will be amazed at this unexpected leap from the materialistic study of history into the arms of monism, in which they were unaware that they ought to have such confidence. Labriola is most careful to avoid this confusion: 'Society is a datum,' he says, 'history is nothing more than the history of society.' And he controverts with equal energy and success the _naturalists_, who wish to reduce the history of man to the history of nature, and the _verbalists_, who claim to deduce from the name materialism the real nature of the new view of history. But it must appear, even to him, that the name might have been more happily chosen, and that the confusion lies, so to speak, inherent in it. It is true that old words can be bent to new meanings, but within limits and after due consideration.