In this case–a gigantic, 188-picture retrospective entitled “Gerhard Richter: Forty Years of Painting” that just opened at the Museum of Modern Art and continues through May 21–the big idea behind his work lumbers through the galleries with you like the proverbial elephant trying not to be quite so noticeable.

Richter, you see, paints in a variety of styles. He does large abstractions with the energy and prolificness of an enfant terrible on a mission to overthrow figurative art. In one five-year period, 1993-98, he cranked out more than 250 of them. But Richter is a figurative artist, too. He paints landscapes, portraits, self-portraits, aerial cityscapes and the odd still-life. So the pachydermic concept with the thunderous footfall is this: can a painter who veers back and forth between emphatically paint-as-paint abstractions (Richter squeegees the stuff across canvases on the studio floor) and a form of painstaking realism be taken seriously as a whole? When somebody asks, “What do you think of Richter?” how many answers are you obliged to give?

MoMA says those questions are precisely the point of Richter’s work, that the artist “has challenged painting to meet the demands posed by new forms of conceptual art.” Conceptual artists–those playful art-world intellects from Duchamp (who posited a bottle rack as sculpture in 1913) up through the contemporary artist Joseph Kosuth (author of a series of works of art on the theme of “Art As Idea As Idea”), and still going with any number of young tyros just out of art school–generally think that visual style is a fool’s game, a relic of the days when art in museums was confined to cast bronze, carved marble and oil paint on canvas. And they think that consistency of style is even worse, that it’s part of the romantic myth about emotionally overwrought artists (think Vincent van Gogh or Jackson Pollock) who just can’t help painting the way they do.

Richter’s bouncing back and forth between gooey abstraction and uptight photorealism is proof, his supporters say, that painting can play the conceptual game, too, and in the process maintain some non-nostalgic clout in the world of contemporary art. As the museum puts it in its press material, the exhibition “vindicates [Richter’s] faith in an art form fewer and fewer of his closest supporters [that is, other artists of a conceptual bent] have believed in and much of the general public has taken for granted.” (That’s to say they’ve figured that just because painting has been around for several hundred years, it’ll be around for a few centuries more.)

Richter was born in Dresden. His father was a Nazi, and so was his “Uncle Rudi,” the subject of one of Richter’s patented black-and-white-and-gray photo-derived portraits (1965). The image has an existential fuzziness provided by the artist’s technique of horizontally whisking still-wet oil paint with a soft brush. Richter himself was enrolled in Hitler youth. But by the time he was 15, World War II was over and he was going a trade school. At 20, on his second try, Richter was admitted to the art academy in Dresden. Within a few years he was employed as part of a team making political banners for communist East Germany–which probably needed a whole lot of them, all the time.

From there, Richter made his way into mural painting which, considered a mere “decorative” art by German Democratic Republic authorities, gave him sufficient freedom to complete enough commissions to provide him with enough money to travel to West Germany. He saw the big international art exhibition, “Documenta 2” in 1959, and that did it. Two years later, just ahead of the building of the Berlin Wall, Richter moved to the real, lower-cased, democratic part of his country.

The best of Richter’s photo-derived pictures pack a punch. They’re as fascinating to look at as, well, old photographs, and there is something about the combination of Richter’s fuzzing technique and, for instance, soft-porn nudes, ugly office buildings, and a “Woman with Umbrella” (1964) that yields a spooky uneasiness. The abstractions are something else. Messy or brushy or gooey abstract paintings carry a presumption of sincerity–perhaps not quite the painter-possessed property of a prime Pollock, but at least some heartfeltness. The conceptual approach–fooling around with abstraction because the idea of fooling around with abstraction seems attractive–doesn’t cut it. Maybe if Richter’s abstractions were in their own show, or at least sequestered in their own galleries, their insincerity wouldn’t be so evident. But as it is, even the three huge (10 by 13 feet) abstractions, “November,” “December” and “January” (1989) with a room to themselves, seem less elegant (which they are) than bombastic. They make a visual “sound” similar to our metaphorical elephant walking across a tin roof. In the end, Richter is pretty good in most of his styles, but not consistently moving or convincing in any of them.

Richter’s work, however, does allude to an even larger issue than the viability of multiple styles in painting. It’s about the impossibility of really seeing. The subjects of Richter’s photo-derived paintings are, of course, doubly removed from real life to begin with, and the painter’s use of out-of-focus grisaille (all grays) triples and quadruples the effect. The longer you look at the picture, the more the subject evaporates. And the impossibility of seeing raises, in turn, the specter of the impossibility of knowing–especially about history, more especially about the history of such characters as Uncle Rudi and what they did during the war. All the German artists of Richter’s approximate postwar generation–Anselm Kiefer, Jorg Immendorf, Markus Lopertz and others–have tried to, well, Deal With It in one way or another. Richter’s solution has been to forego a signature style because–I’ll go out on a limb here–a passionately held, singularly pursued painter’s style contains faint but nevertheless uncomfortable overtones of torchlight parades, Teutonic gods and the politics of hysteria. Best to hold back. Best to be a little distant. Best not to be too sincere. Best to be a conceptual artist.