Writing from Dinant in Brittany in 1863 to his friend, Berthelot, Renan gives his view of the Sciences of Nature and the Historical Sciences. This letter, reprinted in his _Dialogues et Fragments philosophiques_, in 1876, expresses Renan’s.views in a clear and simple form upon the place of science in his mind and also upon the idea of progress, as for him the two are intimately connected. Extreme confidence is expressed in the power of science. Renan at this time had written, but not published, his _Avenir de la Science_. In a brief manner this letter summarises much contained in the larger work. The point of view is similar. Science is to be the great reforming power. The word “Science” is so constantly upon Renan’s lips that we can see that it has become an obsession with mm to employ it, or a device. Certainly Renan’s extensive and ill-defined usage of it conceals grave difficulties. One is tempted frequently to regard it as a synonym for philosophy or metaphysics, a word which he dislikes. That does not, however, add to clearness, and Renan’s usage of “Science” as a term confuses both science and philosophy together. Even if this were not the case, there is another important point to note— namely, that even on a stricter interpretation Renan, by his wide use of the term, actually undermines the confidence in the natural sciences. For he embraces within the term “Science” not merely those branches of investigation which we term in general the sciences of nature, but also the critical study of language, of history and literature. He expressly endeavours to show in the letter to Berthelot that true science must include the product of man’s spirit and the record of the development of that spirit. Renan assumed quite definitely a positivist attitude to metaphysics. “Philosophy,” he remarks, “is not a separate science; it is one side of every science. In the great optic pencil of human knowledge it is the central region where the rays meet in one and the same light.” Metaphysical speculation he scorned, but he admitted the place for a criticism of the human mind such as had been given by Kant in _The Critique of Pure Reason_. Kantian also, in its professions at least, was the philosophy of Vacherot, who stated that the aim of his work, _La Métaphysique et la Science_, was “the reconciliation of metaphysics with science.”[14] These dialogues between a philosopher and a man of science, for of such discussions the book is composed, never really help us to get close to the problem, for Vacherot’s Kantianism is a profession which merely covers an actual positivism. His metaphysical doctrines are superimposed on a severe and rigid naturalism, but are kept from conflict with them, or even relation with them, by being allotted to a distant limbo of pure ideals, outside the world which science displays to us. [14] See particularly his statements to this effect in his Preface, pp. xxxvii-xl.