Here's a thought: Almost every one of us is a collector of contemporary art. Every time we buy a lamp, a sofa, a bookshelf, we're in fact buying art. Most of the time it will be bad art, or derivative art or trivial art -- but art nevertheless. Now imagine if such design objects were made by people whom we already recognize as important makers of fine art. That could improve the chances that some of us, at least, might get to read this article while resting our behinds on masterpieces.

Or maybe not. Maybe design is an art, like music or dance, but not Art, like a painting or a sculpture or a video installation. Maybe art and design have such different pasts -- different histories of who makes them, sells them, buys them, writes about them -- that there's no way for them to share a single present.

A major exhibition at the Smithsonian's Cooper-Hewitt National Design Museum in Manhattan tries to loosen the knots that art and design have gotten themselves into.

Titled "Design Art," the show comes down, more or less, on the side that argues for a yawning gulf between the disciplines. But, more interestingly, it demonstrates how huge a debt is owed to design by important recent art. And how much design could borrow from art, if it thought of going there.

Curatorial director Barbara Bloemink has brought together design objects made over the past three decades or so by 18 important figures in the fine arts. They show that the two disciplines are more crucially intertwined than anyone might think. And yet distinct enough to make their intermixing mean something.

The keystone figure in this exhibition is minimalist sculptor Donald Judd. Almost all the other artists featured were either in cahoots with Judd, in opposition to him or in one way or another his descendants. And this exhibition has made me see him in a new light.

I've always argued, in a roundabout way, for the links between modern design and Judd's minimal forms -- galvanized steel boxes climbing a wall; barely altered plywood cubes. Whenever skeptics have demurred regarding Judd, I've cited the pleasure they get from similarly spare furniture and clothing and cars, and suggested it could be an analogue for the pleasures of minimal art. (After all, do we complain that a black Porsche is excessively pared down? Does anyone want to wear a suit that looks like a Rembrandt?) But "Design Art" leads me to take that position one step further. I'd now argue that modern design isn't an analogue for Judd's sculpture. It is the crucial source of most of its forms, and also the source of some of its meaning.

The exhibition catalogue points out that Judd and his peers collected early gems of modern furniture long before we all were buying knockoffs of them at Ikea. A number of these fine artists also went on to make their own design objects, though mostly as a minor sideline that has received scant attention and that they themselves pooh-poohed. (There was no plus side to being counted a lowly designer.) And way back in 1967, when Judd had barely begun to hit his stride, imperious art critic Clement Greenberg had already insisted that works like Judd's were merely "in the realm of Good Design." Greenberg had seen right to the heart of things, as he often did, but had made the wrong judgment about them. Minimalists didn't "merely" make elevated Good Design. By making things that looked like Good Design, they also made important art.

In 1984, 10 years before his death, Judd got a Swiss metal manufacturer to produce a design he'd come up with for a bookshelf. The piece is in the Cooper-Hewitt show: It's an attractive object, crisp and spare, made of fire-engine-red sheet metal, cut and folded and then assembled with machine screws left exposed for us to see. It is an excellent piece of modern design -- like several thousand other modernist bookshelves and tables and chairs made over the six decades since the heyday of the Bauhaus school, when industrial finish began to take the place of handcrafted decoration. The bookshelf doesn't have the artistic heft of the huge, boxlike sculptural assemblages that Judd almost immediately went on to make, using precisely the same manufacturer, processes and materials he'd first enlisted for his design work.

Judd's great innovation was to take the crucial elements of modern design and transfer them into the world of fine sculpture. Minimalism wanted fine-art objects that would simply keep us company the way all the world's other objects do. Not sculptures to look at or interpret, aloof up there on their pedestals, but foursquare sculptures that could take up space down here alongside us. And the movement found the prototype for just this kind of object in works of modern design. In fact, as the Cooper-Hewitt catalogue points out, furniture, which always tends to the abstract, had also become sleekly reductive decades before fine art did.

I used to think that the minimalists purified the elements of modern design, distilling out color and shape and size and surface so they could be appreciated at their most intense, without the constraints of function. Now, having seen how closely twinned Judd's bookcase and his sculptures are, I've changed my view. It's not so much that Judd purified the design elements he used in his functional objects -- the sheen and crisp edges of sheet metal, the bold hues of commercial paint -- making them "better" and more potent than they could ever be in a decorative-arts context. It's that, simply by presenting those elements as art, he radically changed their meaning, and our readings of them. By ridding them of function, he made them subject to the kind of intense, abstract, fine-artish contemplation that we're taught to give to Rembrandt and Matisse, instead of the casual attention that a bookshelf gets.

This ploy made Judd, for all the notable beauty of his work, count as an esoteric conceptualist, in the tradition of Marcel Duchamp and his bottle racks and urinals presented as art. The difference, of course, is that Judd's Duchampian gesture also paid immense sensory and aesthetic dividends -- the same dividends great design can pay, and that Duchamp's ready-mades were never meant to.

Sculptor Scott Burton, who died young in 1989, claimed to reject Judd's position. Really, however, he just took it one step further. He didn't simply present the elements of good design and then insist that they should count as art, as Judd had done; he did the same thing with the design objects themselves. He wanted to make sculpture that would stay even less aloof than Judd's, and so he made sure that his artworks had function as well as form.

Burton took huge lumps of rough granite and sliced chunks from them so that each would have a highly polished seat and back. (The National Gallery in Washington displays several of these famous "benches," to be looked at and sat on.) In the Cooper-Hewitt show, there are two Burton "sculptures" that duplicate the forms of classic, comfy Adirondack chairs. Burton then covers them in simplifying beige formica.

Burton's sensuous raw granite says "sculpture," even as it asks viewers to take a seat. His simplified deck chair says that it's an artwork that is an image of its Adirondack source -- the black edges in old-time Formica make it look like a line drawing -- as well as having the same function as the thing itself. These are definitely works of art. Burton insisted on this, and, following Judd, they get some of their meaning from this fact. But they do double duty as design objects, and this gives them a novel spin. They share the modern-design roots of Judd's sculptures -- simply as modern chairs, the granite works are not per se that radical -- but they see acknowledging those roots as part of what they're all about.

Which leads us to the one final direction that a contemporary artist with a design interest might take. Instead of borrowing from design but denying function (Judd's move), or asking design to take on the role of functionless, museum-worthy art (a la Burton), truly courageous artists can insist that they'll make superbly inventive works of functional design, and see them as equal to what they make as art.

Of course making truly great design is not an easy ride, even for a big-time artist. For one thing, design's still fishing for the social status art's already got.

Sculptor John Chamberlain still has reason to complain that his fantastic foam-rubber sofas never got the praise they should. Chamberlain was famous -- as an artist -- for freestanding sculptures made of crushed car bodies when, in 1966, he came up with a truly novel take on furniture. Instead of carefully designing an object in advance, then having it immaculately executed, as designers almost uniformly do, Chamberlain borrowed the kind of spontaneity that is standard in art. He took massive blocks of foam rubber, then hacked away at them with an electric carving knife to find the hidden "sofaness" within. Drape the carved block in an old parachute (why waste natural resources on new textiles, when there's fabric with a history available for cheap?) and voila -- for the first time, abstract expressionism that you can lie around on.

And almost no one seemed to notice.

The art world, especially back in the 1960s, didn't want an established fine artist to make seating, especially if it involved leaving behind his trademark crushed-car medium.

The world of design, of course, wasn't watching work by someone in another discipline. And it may not have been ready for the kind of one-off, free-form exploration that, for Chamberlain, seemed the obvious way to go.

With luck, things may have gotten better lately.

Established artist Richard Tuttle -- who's soon to get a major retrospective at San Francisco's Museum of Modern Art -- is famous for the extreme quirkiness of his artworks (bits of barely altered canvas hanging on the wall; oddly gloopy forms carved out of wood). A chair prototype he's showing at the Cooper-Hewitt, titled "Turbulence," lives up to his art's eccentricity. It consists of two cubes of fabric-covered foam joined at a corner; one cube sits flat on the floor, rising to lap height, the other hovers behind it in midair, where you'd expect a back to be. As practical seating, the piece appears useless. Try it out, however, and it turns out to have an absolutely standard, even comfy, feel. Here's an object of design whose form, for once, does not anticipate its function.

There seems a chance that the chair's production version could appeal to today's most forward-thinking furniture buyers, more at least than Chamberlain's sofa did in 1966. And that the art world, less hidebound than it used to be, might accept the chair as a Tuttle sculpture as well.

The most truly daring work in "Design Art" is by Franz West, a well-known Austrian conceptualist. His piece, from 1998, consists of a few absolutely basic pieces of furniture: Two chairs and a table, along with a lamp stuck through the table's middle, all made of construction rebar and cheap plywood. And then, in typical Franz West fashion, there's also an instruction to be followed to complete and complicate the work. Take rolls of brightly colored duct tape, says West, and change and decorate -- or desecrate -- the furniture in whatever way you want, so that it becomes your own.

This is a classic conceptual-art move, where the artist just sets up the preconditions for art to come about, and the viewer is enlisted to finish the job. But when that job involves design, you've got a wholly new beast on your hands.

The double fact of making furniture at all -- Scott Burton's novelty -- and then also giving it an anti-aesthetic, conceptualist spin as well, gives West standing among the art world's avant-garde.

And in terms of fine design, West's work is almost out beyond the cutting edge: Furniture fans still have an awfully hard time with any piece whose finish is deliberately coarse, let alone invokes happenstance and viewer interaction.

Design and art might never be, or want to be, one and the same thing. But sometimes the equation can add up in new ways.

Design Art is on view at the Cooper-Hewitt National Design Museum, 2 E. 91st St., New York, through Feb. 27. For more information visit http://ndm.si.edu.

Richard Tuttle's "Turbulence" chair and Donald Judd's bookcase, both on view at the Cooper-Hewitt National Design Museum in New York. Judd took the crucial elements of modern design and transferred them into the world of fine sculpture. Franz West's "Creativity: Furniture Reversal," at left, lets viewers customize the installation with their own graphics, in the form of colored duct tape. Dan Flavin's porcelain plates, above, and Donald Judd's "Bed #87" are also among the juxtapositions of art and design on view at the Cooper-Hewitt.