J. DELBCEUF, LE SOMMEIL ET LES REVES. 115

ential as opposed to the rationalistic phenomenism. Although not made in the interests of a pantheistic view, it serves to rescue pantheism, as formulated by M. Eenouvier, from the contradiction he finds in it. M. Eenouvier, however, according to Mr. Hodgson, is right in everything but neglecting the background of knowledge, of which the necessary existence is revealed only in perception. The infinite, in Mr. Hodgson's sense, has no place in mathemati- cal or any other science, but forms the inevitable background of all definite knowledge ; practically, the infinite, when dealt with by thought, becomes what M. Eenouvier wishes to substitute for it in all cases a " possible indefinite ". The section in which M. Eenouvier discusses the antinomy of infinite and finite is, it may be added, one of the most valuable parts of his book. The real matter in dispute is disentangled from the complications of scientific hypotheses, and is shown to be a rational question, which, if it is to be solved at all, will not be solved by the mere " progress of science " independently of philosophic reflection. It is above all in making clear the true character of questions of philosophic criticism such as this, their fundamental position with regard to the sciences, their persistence throughout all stages of scientific development, and their insolubility except by criti- cism applied directly to consciousness, that the merit and distinc- tion of M. Eenouvier's method consist. Whether we are able to accept his solution of any particular philosophic problem or not, his statement of it may always be taken to be, as far as it goes, perfectly logical, and an indispensable basis for further study. THOMAS WHITTAKEK. Le Sommeil et les Reves, consideres prindpalement dans leur rapports avec les Theories de la Certitude et de la Memoir e. Par J. DEL- BCEUF, Professeur a 1'Universite de Liege. " Le Principe de la Fixation de la Force." Paris : F. Alcan, 1885. Pp. vii., 262. The name of Delbceuf is less widely known in this country than it deserves to be. His works in logic and psychology mark him out as a writer of sound knowledge and of remarkable pene- tration. The present volume, briefly noticed on its appearance in MIND, x. 472, is, by reason both of its topic and its mode of handling this, very well fitted to give an impression of the writer's qualities as an observer, a thinker and an expositor. No class of psychical phenomena has received less illumination from science than dreams. Some psychologists pass them by altogether, while others are apt to deal with them in a very hasty and superficial manner. The reason of this neglect is not far to seek. In the nature of the case the facts are exceedingly difficult to reach. Even if it is true that sleep is a continuous state of dreaming, it is no less true that comparatively few dreams persist after waking with a distinctness fitting them to be the