Ostwald is one of the founders of the theory of “Energetics,” the theory of the school that believes in substituting a dynamical philosophy, for the older, atomic, or mechanical philosophy of matter and motion. He put this philosophy forward in 1895 as the last gift of the nineteenth to the twentieth century. He suggests how this idea of energetics may be applied also to psychical processes, in so far as these may be understood by conceptions that have proved to be useful in our interpretation of the physical world. Our “consciousness would thus come to be looked upon as a property of a peculiar kind of energy of the nerves.” The whole idea is a piece of phenomenalistic positivism, and although Ostwald makes an attempt (somewhat in the manner of Herbert Spencer) to explain the “forms,” or the categories, of experience as simply “norms” or “rules” that have been handed on from one generation to another, he does not occupy himself with ultimate philosophical questions about the nature either of matter or of energy. His _Natural Philosophy_ has recently been translated into English (Holt & Co., 1910). Its Pragmatism lies in the fact of his looking upon concepts and classification as “not questions” of the so-called “essence” of the thing, “but rather as pertaining to purely practical arrangements for an easier and more successful mastery of scientific problems” (p. 67). He also takes a pragmatist, or “functional,” conception of the mental life towards the close of this book. Professor Ostwald lectured some years ago in the United States, and his lectures were attended by students of philosophy and students of science. Professor (now President) Hibben has written an interesting account of his theory in its philosophical bearings in the _Philosophical Review_, vol. xii. [69] The philosophy of Avenarius (born in Paris, but died as Professor of Inductive Philosophy in Zurich) is called “Empirical Criticism,” which differs from Idealism by taking a more realistic attitude to ordinary human experience. There is an excellent elementary account of Avenarius in _Mind_ for 1897 by Carstanjen of Zurich. Avenarius goes back in some respects to the teaching of Comte as to the need of interpreting all philosophical theories in the terms of the social environment out of which they come. [70] _Logic_, vol. ii. p. 17. English translation by Miss Dendy. In this same section of his work, Lotze talks of the demands of our thought as “postulates” whose claims rest in the end upon our will--_auf unserm Wollen_. [71] To be traced to Fichte’s well-known initial interpretation of Kant from the standpoint of the Practical Reason of the second “Critique,” and to Schelling’s late “positive” philosophy, and to Schopenhauer, the will philosopher _par excellence_. See my _Schopenhauer’s System in its Philosophical Significance_.