Aesthetic, then, as the science of expression, has been here studied by us from every point of view. But there yet remains to justify the sub-title, which we have joined to the title of our book, _General Linguistic_, and to state and make clear the thesis that the science of art is that of language. Aesthetic and Linguistic, in so far as they are true sciences, are not two different sciences, but one single science. Not that there is a special Linguistic; but the linguistic science sought for, general Linguistic, _in so far as what it contains is reducible to philosophy_, is nothing but Aesthetic. Whoever studies general Linguistic, that is to say, philosophical Linguistic, studies aesthetic problems, and _vice versa_. _Philosophy of language and philosophy of art are the same thing_. Were Linguistic a _different_ science from Aesthetic, it should not have expression, which is the essentially aesthetic fact, for its object. This amounts to saying that it must be denied that language is expression. But an emission of sounds, which expresses nothing, is not language. Language is articulate, limited, organized sound, employed in expression. If, on the other hand, language were a _special_ science in respect to Aesthetic, it would necessarily have for its object a _special class_ of expressions. But the inexistence of classes of expression is a point which we have already demonstrated. [Sidenote] _Aesthetic formulization of linguistic problems. Nature of language._ The problems which Linguistic serves to solve, and the errors with which Linguistic strives and has striven, are the same that occupy and complicate Aesthetic. If it be not always easy, it is, on the other hand, always possible, to reduce the philosophic questions of Linguistic to their aesthetic formula. The disputes as to the nature of the one find their parallel in those as to the nature of the other. Thus it has been disputed, whether Linguistic be a scientific or a historical discipline, and the scientific having been distinguished from the historical, it has been asked whether it belong to the order of the natural or of the psychological sciences, by the latter being understood empirical Psychology, as much as the science of the spirit. The same has happened with Aesthetic, which some have looked upon as a natural science, confounding aesthetic expression with physical expression. Others have looked upon it as a psychological science, confounding expression in its universality, with the empirical classification of expressions. Others again, denying the very possibility of a science of such a subject, have looked upon it as a collection of historical facts. Finally, it has been realized that it belongs to the sciences of activity or of values, which are the spiritual sciences.