It is possible that the old heading “Arts and Sciences” has been responsible for some of the barrenness which is so conspicuous a feature of æsthetic theory. For the heading seems usually to have suggested, not only that there is a difference between the arts and the sciences, but that the difference is of a fundamental kind. For the purposes of æsthetic theory the various arts are assumed to have more in common than any one of them has with any of the sciences. We find the writer on æsthetics expounding his principles in chapters headed Painting, Sculpture, Poetry, Music; but it is rare indeed to find the argument extended to mathematics and physics. Yet there is no evidence that such omissions are due to deliberate reflection; the philosopher has not decided, after examination, that the sciences are unæsthetic objects; we must assume that accidents of taste and education have prevented him from paying attention to what may conceivably be useful data for the formulation of a theory of æsthetic. Within the last two or three generations scientific men have been thinking and writing a good deal about the philosophic basis and implications of their study, and it is significant that this inquiry has led many of them to insist on the æsthetic character of the satisfactions that science affords. The late Henri Poincaré, in particular, has shown that scientific theories are akin to works of art, and in this country, Dr. Norman Campbell has asserted his belief that great men of science are essentially great artists. The point of view is an interesting one, and suggests that fresh light may be thrown upon æsthetic problems by a new grouping of their subject-matter. Instead of putting the arts and the sciences on opposite sides of the fence, it may be helpful to see whether certain members of these two groups have not a natural affinity with one another, and so gain hints for a different and more comprehensive classification. It is noteworthy, in this respect, that music has always occupied an exceptional position among the arts. Pater tried to relate it to other arts by saying it was the art to which all others aspire: The arts may be represented as continually struggling after the law or principle of music, to a condition which music alone completely realises; and one of the chief functions of æsthetic criticism, dealing with the products of art, new or old, is to estimate the degree in which each of these products approaches, in this sense, to musical law.