We have now reached a point when we are able to give ourselves an exact account of the signification and importance of the celebrated war waged for over a century in Germany between the Æsthetic of content (_Gehaltsästhetik)_ and the Æsthetic of form (_Formästhetik_); a war which gave birth to vast works on the history of Æsthetic undertaken from one or other point of view, and sprang from Herbart's opposition to the idealism of Schelling, Hegel, and their contemporaries and followers. "Form" and "Content" are among the most equivocal words in the whole philosophical vocabulary, particularly in Æsthetic; sometimes, indeed, what one calls form, others call content. The Herbartians were specially given to quoting in their own defence Schiller's dictum, that the secret of art consists in "cancelling content by form." But what is there in common between Schiller's concept of "form," which placed the æsthetic activity side by side with the moral and intellectual, and Herbart's "form," which does not penetrate or enliven, but clothes and adorns a content? Hegel, on the other hand, often gives the name "form" to what Schiller would call "matter" (_Stoff_), that is, the sensible matter which it is the business of spiritual energy to dominate. Hegel's "content" is the idea, the metaphysical truth, the constituent element of beauty: Herbart's "content" is the emotional and intellectual element which falls outside beauty. The Æsthetic of "form" in Italy is an æsthetic of expressive activity; the form is neither a clothing nor a metaphysical idea nor sensible matter, but a representative or imaginative faculty with the power of framing impressions; yet there have been attempts to confute this Italian æsthetic formalism with the same arguments that are used against German æsthetic formalism, a totally different thing in every respect. And so forth. Having given a plain account of the thoughts of the post-Kantian æstheticians, we shall be able to appreciate their opponents without seeking light from their obscure terminology or allowing ourselves to be misled by the banners they wave. The antithesis between the Æsthetic of content and that of form, the Æsthetic of idealism and that of realism, the Æsthetic of Schelling, Solger, Hegel and Schopenhauer and that of Herbart, will appear in its true light, as the lamily quarrel between two conceptions of art united by a common mysticism, although one is destined almost to meet with truth during its long journey, while the other wanders ever further away.