Kelly's coup.

Standing in front of Ellsworth Kelly's recently painted canvas, Red Curves, 1995, (among the latest works included in the Guggenheim retrospective), with its inimitable irregular shape resulting from the offset encounter of two most regular contours (two arcs), one cannot but wonder how it could feel so fresh, so oblivious to doubt, so joyful even, given the number of monochrome shaped panels the artist has produced, from the '50s on. Each time it's the same tease (just enough complexity for the simplicity to emerge as an unexpected gift, just enough simplicity for the force of the effect to strike the viewer as utterly unaccountable), the same apparent effortlessness. Each time the shape heralds its absolute singularity.

Robert Delaunay called his Simultaneous Disk of 1913-14 a "coup de poing" ("blow with a fist"): he was right, of course, but this work, which has a lot in common with Kelly's enterprise, being perhaps the first noncompositional canvas in 20th-century art, was a fluke (Delaunay left the ring immediately after this single blow, never to grasp its efficacy). I know nothing about boxing, and certainly do not want to dwell on metaphoric machismo, but the idea of the punch is apt, in that it is something that leaves you speechless (my precise state in front of the 1986 Red Curve in the Meyerhoff Collection, or the 1991 Yellow Panel with Curve in the Pulitzer Collection). The boxing imagery also underlines the merits of endurance, one of Kelly's most striking qualities as an artist. Upon seeing his work for the first time, in his early Paris years, Alexander Calder admired it but said, "I want to see what he can do in ten years." Kelly took the advice implicit in Calder's statement to heart.

But what is the secret of such endurance? It might have to do with the fact that Kelly has always been something of a loner. To start with, he fell between the cracks of common historical divides, reaching maturity between the Abstract Expressionist generation and the next, that of Pop and Minimalism (as a result he was always a bit ahead of fashion, and his work was often belatedly recognized as that of a forerunner, but rarely in its own right). And he made his debut in Paris (1948-54), knowing very little of what was happening in the U.S. and with almost no local support (he sold next to nothing during those years, which did not prevent his supposed "Frenchness" from being held against him when he returned to New York). One had to build up resistances in such a context (or lack thereof). But most important, I would say that what I call Kelly's "initial program," something to which he remained faithful all his life, was like Ariadne's thread: What is the use of such thread if it does not endure?

In the aftermath immediately following World War II, the Minotaur, Kelly was quick to perceive, was the protean Picasso. A means had to be found to circumvent him and the fact that he had done it all. Picasso's deadly weapon was his capacity to invent: finding a way not to have to invent was a sure way to negotiate the labyrinth. That's exactly what Kelly did during his Paris years, with a straightforwardness that is, in retrospect, stunning: he explored in turn four different modes of noninventing, of noncomposing, of nonaffirming his ego. Single-handedly, Kelly charted many of the options available to Modernist art in the following decades: "transfer," based on the perfect coincidence between field and image (like Jasper Johns, Kelly selected a flat patterned surface in the world and transferred it onto the canvas, covering it entirely; the main difference between the two versions of image-as-field is that Johns' is superlatively recognizable while Kelly's, since it is only a fragment, is ostensibly unreadable); chance and automatism; the modular grid; and the monochrome panel (a means of declaring color as simply as one can). In fact, the only vein he left untouched at the time was that of "deductive structure," discovered by Delaunay in the aforementioned Disk. (The term was coined by Michael Fried, of course, to describe Frank Stella's "Black Paintings" series of 1959, in which the internal structure of the picture is deduced from the shape of the support.) Kelly soon abandoned chance and the modular grid, but he retained transfer and the monochrome panel, or rather combined them into his signature "noninvention" (the oxymoron is intended here), the shaped canvas, a fifth strategy that he began to explore fully only after his return to New York, and through which he was able to recoup the terrain of form without falling back into the trap of compositionality.

This is not the place to allude to all the paths this non-invention allowed Kelly to explore and the way it allowed him to expand the domain he had so exhaustively charted, but two stand out. The first is the extraordinary inversion of attributes one witnesses in the "Angles" series of 1965-66, by which the vertical realm of painting is declared as the field of positive facts, while the horizontal ground of sculpture is investigated as the site of illusionism (in the "Angles" it is the usually "sculptural" horizontality of the panel on the floor - in reality, slightly off the floor - that takes charge of the perspectival illusion that had always been the burden of painting, and it is the usually "pictorial" verticality of the other panel, removed from all wall support, that safeguards the work's status as an object). The second, in the torque monochrome single-panel paintings that began to appear in 1976, is also an inversion: the figure itself recedes while the ground remains neutral. In these pieces, it is their sole configuration, their silhouette, that engenders the illusion that they are tilted in space, as though the figure were its own ground.

I could go on - Kelly's oeuvre is very diverse, even though his mode of thinking allows for periodic returns, canceling any attempt at pinpointing a linear evolution. Better here to state his patience: very early on, he had understood the field of Modernism as an enterprise of motivation (it is against the arbitrariness and subjectivity of "invention"-as-expression that he had coined his various strategies); at the very beginning of his career, he had surveyed this field, seen both its limits and, within those, its vast expanse of fallow territory. Because he was alone then in envisioning all at once the many possibilities it could yield, he had accepted his historical task as that of tilling this land, digging out many unexpected treasures along the way. The patience paid off: in the midst of a general defeatism, Kelly's art remains upbeat.

Yve-Alain Bois is Joseph Pulitzer Jr. Professor of Modern Art at Harvard University. He is a frequent contributor to Artforum.