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NEW BOOKS. 151 expected from the author. Nothing is left out that can contribute to a knowledge of Frederick's views, of the changes they underwent, and of the influences by which they were formed. After an introduction (pp. 1-4) there follow five chapters on Frederick's metaphysical, ethical and politi- cal ideas, two on his attitude to religion and his views on education, and lastly a brief retrospect (pp. 177-82). The effect of the whole is to convey a vivid impression of the great king's unceasing interest in philosophy, and of the way in which he formed his practical aims in the light of general ideas. The independence of his attitude towards his philosophic friends, especially on questions relating to human nature and human lire, is well brought out. Notwithstanding his admiration of the method of Bayle and his general adhesion to the doctrines of Locke, he is found to have always remained to some extent under the influence of the Leibnizo-Wolffian philosophy ; and a certain difference of his attitude to religion from that of Voltaire a diffe- rence which exists also between the German and the French "Enlighten- ment" generally is traced to his Protestant as distinguished from Voltaire's Catholic education. The author shows what an important influence ancient philosophy known to Frederick through translations and especially Stoicism, had on his mind ; and sees in his strenuous ideal, and in his "severe feeling of duty," a realisation of Kant's categorical imperative. Die geschichtliche Entwickelung des Bewegungsbegriffes und ihr voraussichtliches Endergebniss. Ein Beitrag zur historischen Kritik der mechanischen Principien. Von Dr. LUDWIG LANGE. Leipzig : W. Engelmann, 1886. Pp. x., 141. The historical part of this book, although very full, is not offered as a complete account of the development of the conception of motion ; the author's aim being to arrive at the true conception by the help of the his- tory, rather than to give the history for its own sake. After dealing briefly with the conception of motion in antiquity and in the Middle Ages (c. i., pp. 8-16), he divides the rest of his history into three chapters treating re- spectively of the periods "from Copernicus to Newton" (c. ii., pp. 16-83), " from Newton to the Present "(c. iii.. pp. 84-108), and " in the Present and Future" (c. iv., pp. 108-125). There follow two appendices containing applications to special problems. The definition of motion given as the outcome of the whole historical development is change of position of a body relatively to an object of reference. Obvious as it seems, this defini- tion, the author finds, is not even yet applicable without self- contradiction to the actual treatment of motion 'by science ; the older conceptions of an " inherent motion " of bodies and of their " absolute motion " with reference to "absolute space" having left abiding traces in scientific terminology. The contradictions revealed, however, are only apparent, and may be got rid of by a new statement of mechanical and in particular of astronomical doctrines in accordance with the true conception of " the relativity of motion". This the author attempts by means of the subsidiary conceptions which he puts forward of " the inertial system, the inertial scale, inertial rotation, and inertial rest" (p. 118). Zur Reform des Unterrichtes in der Philosophischen Prop'ddeutik. Von Dr. W. JERUSALEM, k.k. Gymnasial-Professor in Nikolsburg. Wien u. Leipzig : A. Pichler's Wittwe und Sohn. Pp. 32. This contribution to the discussion of " philosophical propaedeutic " in the Austrian Gymnasia may be compared with Dr. Meinong's, noticed in MIND, x. 624. Like Dr. Meinong, the authoi regards psychology as the basis of all philosophical study, and complains that it does not get adequate recognition in the present official scheme. He supports the regu-