Æsthetics may be defined as a systematic training to right thinking and right feeling in matters of art, and is made a part of philosophy by A. G. Baumgarten. Its domain, according to Wolff's system, is that of indistinct presentations and the canons of sensuous taste (αἰσθητικὴ τέχνη, from αἰστθάνεσθαι, to preceive and feel). It has, however, developed into a philosophy of the beautiful in nature and art, and, finally, into a science of the (fine) arts based on philosophical principles. Natural beauty, particular works of art, pure, that is, not sensual, beauty, and philosophical questions are sometimes treated thoroughly, sometimes merely touched upon. Applied æsthetics is the accurate description and valuation of particular works of art; technical æsthetics, the training of the art-student in individual productions; art-history, the continuous record of the development of art, according to a definite plan. It is the duty of æsthetics always to seek the deepest grounds of the pleasure derived from art, not only in the laws of nature, but, above all, in those of the mind, and thus to come in touch with philosophy; but the fruitful source of sound judgment is to be found in a correct view of the world of art itself. The student of æsthetics, though he cannot wholly dispense with an insight into the technique of artistic production, or with a knowledge of the varied manifestations of beauty in nature and life, or even with an actual exercise of one kind of art or another, must rely chiefly on a quick perceptive faculty, systematizing talent, and an intelligent appreciation. In this respect æsthetics will, on the one hand, offer more, on the other hand, less than technical treatises on any one art, practical instruction in the exercise of the same, or illustrated art books for everyone.
The Philosophy of Æsthetics.—Æsthetics, as a general science, takes no account of the individual arts. It investigates the physiological and psychological principles of art, the conceptions of art, of beauty, and of the beautiful in art, and develops the universal laws of artistic activity. Clear and orderly thinking, the presupposition of all scientific discussion, is indispensable in æsthetics, the more so because, otherwise, aimless circumlocution and serious errors are unavoidable. All ideas, moreover, concerning æsthetic beauty and the aim of art need to be carefully examined into. Finally, the subjective conditions of the artist, his relation to nature, and the division and classification of the material that lies to his hand must be taken into account.
The Science of the Arts.—In a history of art only the imitative arts and, possibly, music are, as a rule, included; æsthetics, on the other hand, takes in the arts of oratory as well, though mere eloquence, because of its eminently practical character, is generally omitted. Originally, æsthetics was chiefly occupied with poetry, the laws of which are the most easily explained. With poetry the ancillary arts of rhythm and acting are inseparably connected. If vocal music be added to these, we have all those which are the direct, though transient, outcome of voice and gesture. Man, however, soon progresses to the use of musical instruments and gives his artistic productions a permanent existence by means of written notes or marks. The constructive arts, on the other hand, always make use of extraneous material, such as colour, wood, stone, or metal, with results that are not at the same time complete and visible. The graphic and textile arts are grouped with that of painting; with sculpture, ceramics, relief-work, and every kind of engraving; the lesser decorative arts with painting and architecture. The æsthetics of the individual arts does not bear the abstract impress of æsthetics in general; for although it everywhere seeks out the deeper-lying principles of æsthetic satisfaction, it often invades the domain of art-history in search of illustration, in order to prove the laws of art by means of characteristic types.
Systems and Methods.—This peculiar method of dealing with the subject ensures to Æsthetics the position of an independent and valuable science. For this reason various methods and systems have grown up in it, as in art itself, which lay stress on one aspect rather than on another. Idealism loves great subjects, a lofty conception, monumental execution; it looks to find the divine and the spiritual in all things, be it only allegorically and symbolically. It treats æsthetics from above, and guards most effectually against the debasement of art, but is exposed (as was Platonism in philosophy) to the risk of losing itself in abstraction and, moreover, of not giving due importance to the form of art. With æsthetic formalism, on the contrary, this is the most important matter; it does not ask What, but How; it does not look at the content, but at the form which the artist gives it. It defines what forms are "pleasing" in the absolute sense; that is, combine to make up the image of beauty. When, moreover, it goes beyond experience, and confirms the verdict of the senses by that of the mind, it draws, with perfect justice, the characteristic distinction between artistic conception and scientific treatment. Form, however, without content would be empty; it should be rather, as it were, the blossoming of the idea, and a great subject, unless, indeed, it surpass the powers of the artist, gives his genius an impulse towards the highest possible expression. Realism brings into prominence only the truth and palpable actuality of this content. It sets art on a sure foundation and opens the treasures of the visible world of matter. It brings art into living relationship with life and nature, with national characteristics and current ideas, and leads it, through the favouring influence of artistic industries, into the home life of the people. This system, however, does not always safeguard the true worth of the highest art, whose part it is not to imitate, but to idealize reality, to seek its materials in the world of ideas as well as in that of phenomena; which sets a greater, unchangeable truth side by side with one which is lower in this world of experience, and does not, to take one example, regard, after the coarser manner of realistic art, mere fishermen of Galilee, in working garb and with Jewish features, as true and fitting presentations of the Lord's Apostles. It may, therefore, be said with a measure of truth that the chief task of art begins precisely at the point where the truth of nature reaches its perfection. Naturalism, again, goes much further than Realism, in that it not only insists on fidelity to nature, to the point of illusion, in all arts, whether of painting, drama, romance, or other, but also suppresses as far as possible all that is spiritual or supersensuous. Relapse into merest sensuousness becomes, in such case, inevitable. Not anatomical and organic fidelity of presentation, but the nude, with its allurement, then easily becomes of chief importance, and the artistic conception sinks likewise, with regard to other things, to the level of crude naturalism and sensuous pleasure. In so far, however, as Naturalism holds aloof from this abyss, it champions the autonomy of art in order to maintain its independence of religion and morality. It thereby sets itself in open contradiction to Christianity; since all things human, even art, are subject to the eternal law. Artistic expression is indeed neither the act of a blindly toiling genius nor that of an understanding governed by its own laws, but is the act of a free, responsible will. It affects not only the sight and perception of the spectator, but also his mental disposition and his will. It is in this respect that the laws of morality apply to art as a practical calling. Likewise, as against Naturalism, a moral and religious aim in art must be recognized. "Art is its own aim" (art for art's sake), is a principle which holds true only of the immediate or inner aim (finis operis). The work must of course, above all, comply with the laws of the art in order to be a complete work of art. But it may, even so, serve other ends, such as the mental and religious betterment of mankind, and, above all, the glory of God. The systems hitherto referred to are old, and have their source in certain fundamental views of art; those which follow owe their origin rather to reflection and reaction. The names: "Classicism", "Byzantinism", "Orientalism", "Romanticism", "Archaism" and even "Renaissance" (in the ordinary sense of the word) indicate certain tendencies of art, and of æsthetics, which discern the conditions of progress in a reversion to earlier periods of art-development. Witness the æsthetic conceptions of the "Nazarenes", who laid stress on the poetic, national, and religious temper, in contradistinction to academic stiffness and classical coldness, and who, therefore, reverted to the Italian art of the fifteenth century (the Overbeck school). These ideas exercised an important influence upon the Christian art of Germany, down to the period of Steinle and the Düsseldorf school. Pre-Raphaelitism shares with the Nazarenes their predilection for the Early Renaissance, with its fresh-blossoming, freely-evolving simplicity; shares still more their distaste for a narrowing routine and a conventional uniformity. The Pre-Raphaelite Brotherhood (Rossetti, Holman Hunt, Millais), made noteworthy by Ruskin's writings on the subject; sought to give English art a greater independence, fidelity to nature, and poetic spirit, by linking it to the "primitive" painters of Italy. This tendency, which showed itself somewhat earlier than the middle of the nineteenth century, endured, under the name of Æstheticism, partly in England, and partly in America, until the end of the last century (Burne-Jones, William Morris). Its representatives sought chiefly the oldest and best forms of art, and devoted themselves, not without eccentricities, to furniture and draperies. "Individualism" seeks salvation not in history, but in denial of the historical. It is the so-called "Secession", however, which has attracted most attention. Having at first been mainly a social movement of revolt (in Munich), it has tended to eschew learning and aspired to create all things anew, with results which are sometimes original, sometimes astonishing, and occasionally ludicrous. Whether the new style sought for will develop from this, is more than doubtful; never, certainly, from the purely negative theory of the tendency, since it tends to do away with ideas, form, and style. Yet this striving after new forms is not without a certain justification. A somewhat widespread theory, which may be called "Akallism", rejects the old doctrine of the beauty of a true work of art, and aims to set that which has character, or meaning, in the place of the beautiful. As a matter of fact, nearly all writers on æsthetics have made the idea of beauty the foundation of the whole system, and even Jungmann found it impossible to devise a symmetrical system of æsthetics without that idea. There is no need to deny the possibility of devising such a system, but the witness of history is on the side of the so-called æsthetics of beauty. Akallism, however, as a rule, aims at replacing the beautiful not by the great, but by that which is strikingly characteristic, or brutally realistic. Subjectivism threatens scientific æsthetics with an entirely new danger. The forcible emphasis of the subjective side of art, and of the psychological and physiological conditions of artistic expression, is undoubtedly an advance—provided objective conditions and norms suffer no diminution of their rightful sphere. Yet there is a growing tendency to regard all æsthetic principles and judgments as mere fluctuating opinions, and reject all that constitutes system, principle, or definition. Such scepticism, born of spiritual weakness and cowardice, makes an end, once for all, of all science.
A word must be added here concerning the various methods of æsthetics. The older, abstract, treatment of the subject is no longer available, in view of the abundant facilities which perception now has at its disposal. Mere sense-training, however, leads, in its turn, to very superficial knowledge; it is the chief function of perception to prepare the way for mental insight and ideal conception. Nor can we dispense with either the systematic arrangement of the history of art, or the quasi-philosophical basis of æsthetics. The introduction of natural-science methods into æsthetics (Taine, Grant Allen, Helmholtz, Fechner), as well as the close connection between theoretical and practical instruction, and artistic expression (Ruskin), offers great advantages, if not relied on exclusively. At the same time, it remains true that high art can never be wholly dissected by the methods of the exact sciences, but rather itself lays down in turn the governing norms which art expression should follow and, having once attained its proper perfection, is not longer dependent on such expression. The proper subject; therefore, of æsthetics is the great arts; the technique and the theories of the lesser arts have a narrower range of material. As a matter of method, it is advisable to set poetry in the foreground of any discussion concerning art, since it is thereby easier to keep the æsthetics of the other arts from becoming mere technique.
History of Æsthetics.—Socrates, in Xenophon's "Memorabilia" and "Symposium", makes no distinction between the good and the beautiful, and the same indefiniteness extends to Plato's philosophy (The Republic, Phædrus, Philebus) and that of Plotinus (Ennead, I, vi). The idealism of this philosophy not only gave rise to the work of Longinus concerning "The Sublime", but also inspired Dionysius the Areopagite (De Divinis Nominibus) and several Fathers of the Church. Aristotle, on the other hand, gravely analyzed the form and properties of the beautiful as, in his "Poetics", he analyzed the art of epic, tragic, and comic poetry. The acute incidental comments of St. Thomas Aquinas are chiefly confined to the notion of the beautiful and of art, and to the artistic idea. The systematic treatment of æsthetics begins with A. G. Baumgarten's "Æsthetica" (1750–58). However little philosophical value his canons of taste, founded on "confused ideas" and "sensitive perceptions" may possess, as a matter of fact, his book had a stronger influence upon the further development of æsthetics than both English and French philosophy had prior to his time. The former, starting from a Platonic idealism, sank further and further into empiricism and sensualism, and insisted, not too philosophically, on the principle of common sense (Shaftesbury, Hutcheson, Reid, Hume, Burke). Hogarth devoted himself to painting and proposed as the "line of beauty" the curve which bears his name. Among the French, Batteux, following Aristotle, devised a system of the fine arts, which, however, clung somewhat too closely to the principle of imitating nature. Diderot did the same to an even more marked extent, whereas the later French æsthetics approximated to idealism (Cousin). In Germany æsthetics came to be treated of with much zeal after Baumgarten's time, both in a philosophical and in a popular fashion. To allude here only to the first, the art-critics Winckelmann and Lessing were among the numerous followers of the Baumgarten school, the former directing his special attention to the art of sculpture. Kant, again, obtained great influence, and, though his pet theory, that beauty is merely a subjective, formal fitness, found no followers, he stimulated activity in many quarters by means of self-contradictory concatenation of various systems. From him, then, is derived the abstract idealism of Schelling and Schopenhauer, wherein the general idea of beauty is not sufficiently absorbed in the form of its manifestation. Concrete idealism also (that of Hegel and Schleiermacher) owes its origin to Kant. It regards beauty not as a universal idea, but as an individual-evolution. To him, too, may be traced the æsthetic formalism of Herbart and Zimmermann, and "æsthetics of feeling" (Kirchmann).
Hegel, Vorlesungen über die Æsthetik (Berlin, 1835–38); Th. Vischer, Æsthetik, oder Wissenschaft des Schönen (Reutlingen, 1846–57); Deutinger, Kunstlehre (Ratisbon, 1845); Kostlin, Æsthetik (Tübingen, 1863–68); Carriere, Æsthetik (Leipzig, 1885); Idem, Die Kunst im Zusammenhange der Kulturentwicklung (3d ed. Leipzig, 1877–86); Zimmermann, Æsthetik als Formwissenschaft (Vienna, 1865); Jungmann, Æsthetik (3d ed., Freiburg, Baden, 1886); Konr. Lange, Wesen der Kunst (1901); Gietmann-Sorensen, Kunstlehre (Freiburg, Baden, 1899–1903).—In England Ruskin's Modern Painters has had a wide circulation, as have his other numerous works. The following French works may be mentioned: Sutter, Esthétique générale et appliquée (Paris, 1865); Longhaye, Théorie des belles lettres (Paris, 1885).—For the history of Æsthetics: Müller, Gesch. der Theorie der Kunst bei den Alten (Breslau, 1834–37); Zimmermann, Gesch. der Æsthetik (Vienna, 1858); Schasler, Kritische Gesch. der Æsthetik (Berlin, 1872); Von Hartmann, Die deutsche Æsthetik seit Kant (Leipzig, 1886).—For the history of Art: Kraus, Gesch. der christl. Kunst (Freiburg, Baden, 1896–97); Springer, Handb. der Kunstgesch. (6th ed., Leipzig, 1901–2); Kuhn, Allgem. Kunstgesch. (Einsiedeln, 1891, incomplete in 1906); Woermann, Gesch. der Kunst aller Zeiten u. Völker (Leipzig, 1905)—not yet complete.