We cannot follow the author through his ingenious criticisms of Spencer’s great synthetic formula, to which he devotes the twelfth chapter of the present work, and which he characterises as the perfect type of the universal unverifiable hypothesis. Nor can we do more than give a passing glance at his views of the psychology of the three modern systems of philosophy. He affirms that the metaphysical transformation by criticism of psychology into philosophy left hardly anything to the special science. To positivism is due the conception of psychology as forming an integral part of biology, which has led to the important psycho-physical experiments of the present day. But the biological analysis of the individual should be followed by social analysis, the study of mental manifestations in society, in connection with which should be created a special concrete science to embrace the higher psychology, as pointed out by the author in his work “La Sociologie.” Science, art, and industry are a projection into the external world of the thinking, feeling, acting subject, and psychology ought also to be thus projected by fusion with biology, or with biology and sociology, which it is necessary to study if we would discover psychic laws. In the chapter on the Supremacy of Science, the author affirms that the philosophy which will result from the progress of psychology and sociology will present a striking contrast with all known metaphysical forms, but it will always remain a world-conception, and it will have to submit to the law of correlation which explains the character and destinies of its predecessor. Agnosticism, which invites men to bend before the _Deus ignotus_ of all religions, marks the fatal termination of ancient anthropomorphism, influenced by a progressive knowledge, and thus appears as the final integration of all theology. It also represents, however, the condition of incognisance to which the opposite state will succeed when the cycle of abstract sciences is completed and a really scientific psychology formed. Then hypotheses as to universal causes will receive their psychological solution, and it will remain for philosophy only to confront and co-ordinate them with the general results of other sciences. Having arrived at this point M. de Roberty formulates the conclusion that Philosophy and Science are terms which connote two principle _species_ in the vast _genus_ designated by the single term _knowledge_. The most marked trait of future philosophy will be the distinction of these two species, as their confusion was the most general character of the philosophy of the past. Philosophy and science will then be perfectly identified, but the identity will be general and not specific. Thus philosophy will not be positive in the sense of Comte, it will never _completely_ identify itself with science.