Walter Pater, in The Renaissance of 1873, so begins the essay "The School of Giorgione":
It is the mistake of much popular criticism to regard poetry, music, and painting—all the various products of art—as but translations into different languages of one and the same fixed quantity of imaginative thought, supplemented by certain technical qualities of colour, in painting; of sound, in music; of rhythmical words, in poetry. In this way, the sensuous element in art, and with it almost everything in art that is essentially artistic, is made a matter of indifference; and a clear apprehension of the opposite principle--that the sensuous material of each art brings with it a special phase or quality of beauty, untranslatable into the forms of any other, an order of impressions distinct in kind--is the beginning of all true aesthetic criticism.
When I first read this, it shocked me. This idea that each art-form is unique and incomparable is so far from obvious, that to accept it would negate art.
Pater himself was either not audacious enough to pursue the idea, or wrote carelessly and meant something else. Both excuses are implausible; but he must be excused, since this is the same essay that delivers the sentence All arts aspire to the condition of music—which must have seemed profound, before Schoenberg undertook to reinvent music on the model of painting.
Aristotle relied on painting to inform drama, both in extent (not too short, like a painting of a flea, nor too long, like a life-size painting of a monster a mile long) and to supply its content—representation or mimesis—which he justified by the pleasure of any accurate painting, even of something unpleasant. Ut pictura poesis; the Renaissance poet's commonplace that painting is dumb poetry, and Leonardo's unhelpful refutation, poetry is blind painting; Qianlong's exaltation of painting as the model of decoration; Whistler's politely overlooked studies and compositions and symphonies—but enough. More can always be found. Only note that to set a rule for an art, a critic must be able to adduce the material conditions of another art; and to break a rule for an art, an artist must be able to adduce the critical freedom of another.
The depth of this process of making and breaking the definitions of an art by appeal to other arts goes as far back as definitions can be documented. Which art defines which changed; but no art has ever existed alone. (No people, however ancient, are without at least the triangle of music, dancing, and poetry.)
This process of definition by comparison is not only historical or theoretical. Even once definitions are set, it continues at every level of every form. It is no only the origin of art; it is the metabolism of the life of art.
The possibility of combining arts, for example, presupposes the possibility of comparing them. Such composite arts outnumber elemental arts. There are more composite arts than we can name. Music & writing & acting are one kind of drama; music & writing & acting & singing are musicals or operas; music & writing & acting & cinematography are movie; but music & writing & acting & singing & stagecraft & spectacle is as distinct from the simple name musical or opera as these are from plays; yet it goes nameless.
In retrospect, even the arts postulated as elemental are divisible sub-atomically into parts that can be compared: painting, for example, is draftsmanship & composition & coloration; music is rhythm & melody & tone.
Practically, as audience, we regard those arts that require cooperation in their production as essentially composite, and those arts that can be carried out by an individual as essentially elemental; but the possibility of the criticism of an individual artist presumes further fissibility—this painter is a camera, all detail, no balance or flow; this player is a machine, perfect rhythm & perfectly boring.
And to do any criticism beyond rating, we must suppose that even these supposititious pseudo-arts—supposititious because they cannot exist independently; they are seen outside the lab, like strict-sense particles, only in combination—these arts can be compared with each other; for sometimes perfect rhythm, perfect melody, and perfect tone fail to make a perfect fit.
A combination is not simply a sum. It can be better than its parts. In popular music, for example, a good song is, as a rule, the combination of a bad poem with bad music. What it would bore me to read, what it would bore me to play, I find completely satisfying to listen to, so strongly do the ingredients bind together.
But what value remains when we split a composite art? If the composite is simple enough, none; but if the composite is complex, combinations short of the whole may still be worthwhile though the elemental parts are not. A Chinese poem-painting can be appreciated in four ways—accordingly as poetry, calligraphy, and painting are recombined.
Such a relationship between whole and part is a more approachable instantiation of the relationship between whole and whole when a work of one art is translated into a work of another. There are two kinds of artistic translation: when the creator and translator are the same person; and when they are different people. Again, when creator and interpreter are not the same, they may be working collaboratively; or the interpreter may be independent of the creator—part of posterity, even.
When a painter says he wants to paint a poem—so many ladies of Shalott; when a musician wants to score a painting—Tedesco's Goya—when a poet wants to give words to a piece of music—"A Toccata of Galuppi's"; when a musician wants to fit music to words—the "Ode to Joy," Carmina Burana; when a writer wants to fit a story to a poem—"There Will Come Soft Rains"; when a poet wants to fit a poem to a story—"Tithonus" (I take these examples off the top of my head)—we are faced, if the translated work is a success, with something very difficult to criticize. Sometimes the inspiration is plainly tacked on. And the correspondence is not unique—one work may be translated into a single medium several times in several distinct versions. But there is a core of comparability between those versions—silent Romeo and Juliet and a talkie—and between translations into different mediums—Romeo and Juliet as a movie and as a ballet—a core that represents the work abstracted from its medium. This abstracted core cannot be handled directly; but it can be inferred from the signs of its passage.
By translation understand something done to a specific work. There is certainly a sense in which all of a single artist's works resemble each other; and a resemblance between all the art forms of a certain time, place, or class. Such mere affinities are not our concern. They are too tentative and too subjective to analyze: mere family resemblance, we see when we know the relation what we would never seen on our own. Criticism already adduces far too many long-lost cousins; worldly success attracts them during life, but artistic success draws them as it continues to grow in reputation.
Besides whole translation, however, yet above affinity, there is the phenomenon of influence. Influences are, of course, the mechanism of commercial art, which employs art forms together in a relation which is complementary, but not binding. The phenomenon of influence characterizes both artists themselves who seek commercial success—bands, for example, who try to dress like they sound and sound like they dress—and it characterizes the art generated by commerce—the mutual adjustment, for example, of the design necessary to produce a product suitable for advertisement on TV, and the music and direction necessary to produce a TV commercial suitable to the product. This differs from combination because it is unstable. The music and the fashion, the direction and the design, are always pulling one another in a way that ensured both a perpetual movement like a mathematical pattern's towards an unattainable attractor, and sudden phase-shifts when the old elements, having become too well adjusted, make room for a new element that reboots the process—shifts that approximate the succession of new generations to commercial relevance.
(We are used to thinking, in an afterthought Marxist way, that because the faddishness of commercial art serves commerce, it must therefore a consequence of commerce. But we should be past the idea that commerce can create phenomena of human behavior. It can only exploit them. The fad, the fashion, novelty and mode are a permanent possibility of art, though not one always acted out; part of the definition not always realized, like the introns of genetics that code in birds for the scales and teeth of dinosaurs and show up sometimes as deformities.)
But taxonomy is not demonstration. To list the ways in which arts can be compared—criticism, combination, translation, influence—is not to prove that all arts are comparable. But I see no way to define art as such, as distinct from creativity generally, except that art is what can be compared to an art, being the more like an art the more easily and confidently it can be compared. This compasses everything now called, or ever called, art, as well as all extant theories of art—they being reducible to acts of comparison.
Of course, that a definition is comprehensive does not make it true. It may even be a fault, if the definition has no limits. This definition, however, does have some limits. It does not pretend that arts can be recognized by themselves; the act of comparison is necessary. In this it evades the supernatural insight into intentions supposed by the idea that anything is art that is meant to be art. It does not declare that everything is art, nor even that everything now considered art always has been art; it is the act of comparison, not the possibility, that makes an art an art. It also, uniquely, provides for the historical development of arts out of one another, without tabulating which art is ancestral to which: it provides for the fact of a tree, without dictating its shape.
That is not a deductive proof; but I will settle here for induction. Induction better suits an essay.