Formalist art criticism is the oldest known form of critiquing works of art, which dates back roughly to the Enlightenment era in 18th-century France, when philosopher and critic Denis Diderot began offering informed judgments of paintings. (Art criticism should not be confused with Aesthetic Theory, which is far older. However, the two are inextricably linked.) Diderot and subsequent French writers such as Charles Baudelaire, André Malraux and Guillaume Apollinaire all furthered the practice of formalist criticism, which was essentially the writerly art of determining an artwork's intrinsic value based on its aesthetic qualities.

• A painting's form was composed of its basic elements: color, line, composition, and texture. These elements constituted the fundamental language used by formalist art critics to examine and analyze works of art.
• Whether an artwork was a pure abstraction or figurative, a formalist looked for the same basic elements and judged a painting's value based the artist's ability to achieve a cohesive balance in the composition.
• If a painting was deemed deficient in value, it was because the artist had failed to create a visual balance of the formal painterly elements.

Philosopher Plato developed a Theory of Forms based on the idea of eidos, roughly translated to mean "stature" or "appearance." Plato applied the term broadly in his various dialogs to suggest a rudimentary universal language. Every earthly object, he posited, whether tangible (like a chair) or abstract (like human virtue), shared one aspect: they all had a form.

Plato's Theory of Forms can be best understood through his "Allegory of the Cave." He envisioned a cave in which resided prisoners who had been held captive their entire lives; all they could see were the shadows of workers cast along the cave's walls, and all they could hear were the echoes of their voices resonating throughout the cave. Since this was all they knew, the prisoners perceived these shadows and echoes as the actual form of real objects, and were therefore completely unaware that those forms were just mimicries of the real things. Plato ultimately stated that the prisoners' perception of things was not false; by their understanding of the world, the shadows and echoes were the actual forms, just as a painting of a woman is as real, if not more real, than the actual woman who is depicted on the canvas.

In the early 20th century, modern artists experimenting with styles of Fauvism, Expressionism and Surrealism, were influenced by many of the problems raised in Plato's Theory of Forms. The most profound of these problems was humankind's attempt to reconcile permanence and change, which invited the following questions: How can the world appear to be both permanent and changing? If the world we perceive through the senses seems to be always changing, and the world that we perceive through the mind seems to be permanent and unchanging, then which of these perceptions is more real? And how can we explain the existence of both?

In 1843, British art critic John Ruskin (at age 24) published the first of five volumes of Modern Painters, in which he offered high praise of the Impressionist-like paintings of J.M.W. Turner. It was arguably at this time when formalist art theory in the modern era began. Turner's art was considered by many to be messy and meaningless, given the artist's tendency to blur the visual boundaries between figuration and accurate representation of natural forms. Ruskin, however, argued that Turner's paintings had achieved a more accurate portrayal of nature than any other artist before him.

Of Turner's work Ruskin wrote, "Turner's sails have no beauty about them like that of Alpine bridges; but they have the exact switchy sway of the sail that is always straining against the wind .. Now observe how completely Turner has chosen his mill so as to mark this great fact of windmill nature; how high he has set it; how slenderly he has supported it.." These excerpts are strong examples of formalist criticism, wherein Ruskin is making informed judgments based solely on the artist's composition of natural forms.

Turner's work was instrumental in the development of French Impressionism, made famous by artists such as Claude Monet, Pierre Renoir and Paul Cézanne, among others. The coining of the term 'Impressionism,' interestingly, was a seminal moment for formalist criticism. 'Impressionism' was first used in a review written by French critic Louis Leroy, meant as a derogatory term to describe the work of Monet, who had entitled one of his paintings Impression, Sunrise (1872). This was the first recorded time when a new artistic movement was named not by participating artists, or retroactively by scholars, but by a contemporary art critic. This is both a uniquely modern phenomenon and a key example of formalist criticism at work.

Man Ray, the American Dada and Surrealist artist, issued a statement in 1916 for The Forum Exhibition of Modern American Painters at the Anderson Galleries in New York in which he wrote, "The creative force and the expressiveness of painting reside materially in the color and texture of pigment, in the possibilities of form invention and organization, and in the flat plane on which these elements are brought to play. The artist is concerned solely with linking these absolute qualities directly to his wit, imagination, and experience, without the go-between of a 'subject.'"

Ray's point here stressed the importance not only of the artist's ability to link these "absolute qualities" on the picture plane, but also of his ability to create something visually captivating independent of anecdotes and contextual subject matter; what we commonly know to be the subjects of pre-modern art. What Ray was stressing here was both the importance of the artist's ability to link these "absolute qualities" on the picture plane and his ability to create something visually captivating, independent of anecdotes and contextual subject matter.

In the early 1940s, the artists Mark Rothko, Barnett Newman and Adolph Gottlieb issued a statement in The New York Times, in which they wrote. "We do not intend to defend our pictures. They make their own defense. We consider them clear statements .. We refuse to defend them not because we cannot. It is an easy matter to explain to the befuddled [critics] that The Rape of Persephone is a poetic expression of the essence of myth..the impact of elemental truth. Would you have us present this abstract concept, with all its complicated feelings, by means of a boy and girl lightly tripping?"

Rothko, Newman and Gottlieb essentially believed that any attempt to deconstruct and subsequently explain an abstract work of art was essentially to strip it of its intrinsic value. The ultimate meaning of an abstract work was to be found in its very form - its shapes, colors, lines, etc. - and through the acceptance that "art is an adventure into an unknown world." By trying to explain this world, critics were attempting to apply common sense to something that defied that very thing. Collectively, the work of these three and other New York artists had turned increasingly abstract to the point where abstraction became a painterly form in itself. Since abstraction was form, then it was by design self-explanatory and, according to the statement, comprises its own defense.

Clement Greenberg is considered the foremost formalist critic of mid-century, and like Rothko and company, he believed that any analysis that searched for deeper meaning (context, subject matter, etc.) in abstract art went against the ethos of formal art theory. Greenberg was a formalist because he analyzed art based solely on the elemental truths of the artwork. A line is a line and a square is a square; the only important truth when considering these elements was the visual impact they had on the viewer.

Much as Greenberg's formalism was an examination of an artist's ability to visually balance the elemental forms on the canvas, it was also a judgment of that painting's purity of medium and style. Greenberg soon concluded in his own writings that abstraction was the purest form of art because the abstract image was self-explanatory; it existed on its own merits and contained no hidden meaning. Greenberg also concluded early in his career that abstract art, unlike many of its stylistic predecessors such as Impressionism and Fauvism, did not blur the boundaries between various art forms. By this, he meant that certain forms could employ elements of other styles, but there was no confusing a work of pure abstraction as anything other than precisely what it was.

There were several critics and theorists during the era of Abstract Expressionism who adopted less formalist-based approaches to critiquing art. These critics included Harold Rosenberg, Thomas B. Hess and Leo Steinberg. However, arguably no other critic challenged formalist art theory more so than Robert Rosenblum. A prolific critic, professor and curator for most of his life, Rosenblum redefined the history of Modern art by stretching the historical boundaries of Modernism to include 18th-century Baroque and Neo-Classicism. By doing so, Rosenblum conveyed that all Modern art forms were integrated into one large historical canon, whereas traditional formalism maintained that Modern art was comprised of a gradual evolution of increasingly abstract and non-representational styles, beginning with Impression and, according to Greenberg anyway, ending with Abstract Expressionism.