In a mature career of eight feverishly productive years, Morris Louis made an astonishing number of the most ravishing, mysterious, unyieldingly abstract paintings of the twentieth century. Between 1954 and his death, aged fifty, in 1962, Louis produced about six hundred large paintings composing the series known as Veils, Unfurleds, and Stripes, among others. These works are so authoritatively present that they compel our attention, and so disembodied that they appear to be pure essence. The confrontational Veils with their implacable "curtains" of layered hues, the tense Unfurleds with their wide-spaced cascades of clear chroma and empty centers, and the economical Stripes with their disciplined ranks of exuberant color, all seem based on a desire to reduce painting to its essentials without sacrificing its ability to stir us.

Louis's pictures test both the autonomy and the expressive potential of color, expanse, interval, and shape; they even seem to test whether the fact that paint is liquid can be eloquent. Louis's abstractions completely disassociate the raw materials of painting from reference, just as they disassociate gesture from handwriting, yet there is nothing impersonal about the result. Even in pictures that at first reading appear to be nothing more than floods of thinned-out pigment, responding to the dictates of gravity, we're aware of the intuitive intelligence that made that wash of color assume the configuration before us. Louis's pictures stop us in our tracks by their size and grandeur. They seduce us by the subtleties of their hues. Their lucid, symmetrical compositions suggest that they might be knowable, if we concentrated, yet ultimately they seem to remain just out of range, hovering at the limits of perception and emotion, sometimes profoundly moving, sometimes exhilarating, always enigmatic and always beautiful.

Like those of his colleagues Helen Frankenthaler, Kenneth Noland, and Jules Olitski, Louis's paintings define Color Field painting: the apparently detached but visually opulent abstraction that evolved in post-World War II America--abstraction in which the deployment of surprising hues takes precedence over almost every other aspect of picture-making, so that expanses of color and their relationships assume the burden of associative meaning. (It's worth noting here that while Louis belonged to the Abstract Expressionist generation--he and Jackson Pollock were coevals--Louis found his distinctive voice through his connections with younger artists, particularly Noland, twelve years his junior, and the even younger Frankenthaler, whose uninhibited stain method profoundly influenced both men.) Color Field painting at once continues, expands, and challenges the assumptions of Abstract Expressionism--at least, of the non-gestural strain embodied by the work of Pollock, Mark Rothko, and Barnett Newman. Like their older colleagues, the Color Field painters believed that the source of creativity was the unconscious and that the painter's role was to reveal the unseen rather than to report on the visible. But where Abstract Expressionism traced its angst-ridden roots to Picasso, Cubism, and Surrealist theory, the Color Field painters were more sympathetic to Matisse and more indebted to his example. Matisse's work not only asserted the primacy of color, but also...