Marcel Duchamp (1887-1968) was the most influential artist of the 20th century. To have said as much during most of that century would have marked the speaker as an absurdist or a cultist. Pablo Picasso and Henri Matisse were the great artists and, indeed, they were. Their invention and prodigious output in nearly every artistic medium made them living monuments of creativity.

But today, neither carries much weight among living artists. Nearly everyone is a Duchampian — even if they don't know it.

One of the great aesthetic subversives, Duchamp changed the way art is perceived, from something of the eye to something of the mind. He rejected the "retinal" for what Leonardo da Vinci, his role model, called "una cosa mentale" — a mental thing.

As art historian Francis Naumann put it last week during a symposium at the Chess Club, when turn-of-the-20th-century viewers saw works by Matisse and Picasso they were able to process them by looking at them as they had looked at paintings for centuries.

But when Duchamp exhibited a bicycle wheel mounted on a wooden stool, they had to think first: Why is this in a gallery? Does the fact that it is in a gallery make it art? How do I look at it?

In the early decades of the 20th century, Duchamp made a couple of works that still provoke. He signed (as R. Mutt) an industrially manufactured porcelain urinal as a sculpture to, among other things, suggest that any object was a work of art if the artist said it was.

He drew a crude mustache on a cheap lithographic copy of the Mona Lisa to thumb his nose at the idea of hand-made mastery of any sort.

But then, in 1923, he renounced art-making for chess. Or so he said. In fact, he never totally gave up making art; during the last 20 years of his life, he worked secretly and relentlessly on a variety of projects.

The fascinating exhibition at the St. Louis University Museum of Art presents Duchamp the chess player. Organized by SLU professor Bradley Bailey, a Duchamp specialist, it is the first exhibition ever mounted anywhere on the subject and the first solo exhibition devoted to Duchamp in St. Louis. Its opening coincided with the United States Chess Championship, held in St. Louis for the first time. The championship concludes Sunday.

The show is small, but choice. Bailey refrained from including works that have no connection to chess. Every work here directly addresses the theme. That might not sound like much, but the exhibition world abounds in shows padded with extraneous material. The restraint shown here is praiseworthy.

For example, Duchamp is famous for his ready-mades — works like "Fountain," the signed urinal. A Duchamp show without a ready-made would be missing something. The ready-made here is "Trebuchet (Trap)" (1917/1964), a four-hook coat rack originally nailed to the floor. It is one of the lesser-known works made from commercially available objects of no apparent aesthetic value. It is named after a chess move — a sacrifice made in the hope that the opponent will make a disadvantageous move.

From 1923 to 1933 chess dominated Duchamp's life. He competed professionally and came in first in a French national competition in 1924. He was awarded the title of Chess Master by the French Chess Federation. When he died, Le Figaro published his obituary in its chess column.

Duchamp had contradictory ideas about the relationship of chess and art. If art was a thing of the mind, why couldn't chess be considered art?

In 1959, he asked Truman Capote: "Why isn't my chess playing an art activity? A chess game is very plastic. You construct it. It's mechanical sculpture, and with chess one creates beautiful problems, and that beauty is made with the head and hands."

But in Chess magazine in 1961, he seems to have changed his mind:

"Chess is a sport. A violent sport. This detracts from its most artistic connotation."

The SLU show should appeal to both art and chess lovers. There are three chess sets, each made by a major dada or surrealist artist — Salvador Dali, Max Ernst and Man Ray — each following dada or surrealist procedures.

Dali, for instance, used his finger for the king and that of his wife and muse, Gala, for the queen, each crowned by a tooth — pun intended — cast in bronze.

Duchamp's set was less playful. He made a small pocket set, one from a projected large edition, another of his unsuccessful business ventures, as the wall text points out.

There are lots of photographs of Duchamp and his cohort playing chess, and posters and other ephemera that refer to the game.

The most important work on view is "La Boite-en-valise," literally "The Box in the Suitcase," a traveling case filled with reproductions of his major works that Duchamp made from 1935 to 1941. The one on view includes one unique piece, an item titled "La Fourchette du Cavalier (The Knight's Fork)," a reference to the chess piece. There are also four reproductions of chess-themed works from Duchamp's oeuvre.

Although there's no scientific truth to back up the assertion, seeing the show, like playing chess or listening to Bach, may make you smarter.