ohn Baldessari's art prods imagination. His parables-in-pictures invite your mind to play. It requires mental hopping -- from the tiny to the vast, from the tragic to the goofy, from the now to the remembered -- to get what he is getting at. To read his broken narratives you have to think askew.

Askewness is, in fact, the subject of a photo work composed by Baldessari in 1972-1973. Now on exhibit in his touring retrospective at the Hirshhorn Museum and Sculpture Garden, it's based on a story told by Nellie Monk, then Mrs. Thelonious. The pianist, she recalled, once "nailed a clock to the wall at a very slight angle, just enough to make me furious. We argued about it for two hours, but he wouldn't let me change it. Finally, I got used to it. Now anything can hang at any angle, and it doesn't bother me at all."

Baldessari's piece, accordingly, is a little off. "A Different Kind of Order (The Thelonious Monk Story)," is a sequence of news photographs of natural disasters -- of telephone poles a-toppled, and houses jumbled by an earthquake, and fishing boats half sunk. The frames that frame these images are themselves atilt. They jitter on the wall.

He loves to tweak the rigorous. Here is one example: It's easy to blow smoke rings. But have you ever tried emitting fresh puffs of cigar smoke that imitate not circles but the far more complex shapes of far-off fleecy clouds? Baldessari has.

Baldessari seldom paints. Instead he tends to work with "appropriated" photographs, or snippets cut from photographs (he often uses movie stills), displayed in tale-telling groups, frequently with texts. His pieces feel severe at first. They are warmer than they look.

He was born in 1931 south of San Diego in National City, Calif. Until a few years ago, he was as well known for his teaching as he was for his art. Baldessari taught from 1970 to 1987 at the California Institute of the Arts. Many are the art stars -- David Salle, for example, Jenny Holzer and the Starn Twins, Barbara Kruger and Matt Mullican -- that he instructed at CalArts or more distantly inspired. Now he's an art star too.

But not one of the usual sort. For one thing, he is taller. Baldessari is 6 feet 6. For another, he is older. He turned 59 in June. His work is gentler too. He makes kind conceptual art.

Those terms are seldom linked. The best conceptual art of recent years is intellectually strict. That of Joseph Kosuth investigates phenomenology. It rarely makes you grin. That of Sol LeWitt (whom Baldessari calls "an exemplary artist") explores the hidden truths that lurk within the purities of rigorous geometries. Baldessari deals with griefs and joys and wonders. His affirmative-subversive, always-oscillating art twinkles in the gap between the abstract and the heartfelt. You might say that his subject is what it's like to be alive.

His arena is the in-between. He's as interested in the glance as he is in the glancer. His eyes wander when you speak to him. He tends to look over your shoulder. He says, "When I started out, I tried to look between objects, not at objects. It wasn't good for driving, but it trained my eye." What are the hidden bonds that tie people into crowds, or, in contrast, dissolve crowds into individuals? "What's a whole and what's a part?" he asks. "What's broken, what's complete?" And how does one make manifest the resonance of rhyme? What, for instance, ties the cruel arc of an eagle's beak to the tender sweep of a mouse's whisker? His pictures often pun.

"For most of us," he's said, "photography stands for truth." But Baldessari takes those truths, those photographs-as-facts, to conjure ambiguities. He's said, "It fascinates me how I can manipulate the truth so easily by the way I juxtapose opposites or crop the image or take it out of context. When two forces contend in a photograph, I may favor one side or the other -- the rider or the horse, for example; the upright mummy in its coffin or the woman standing in awe next to it. Cropping can make the outcome of a struggle ambiguous."

The eerie interplay between accident and plan is curious to him too.

In 1971, while visiting Pier 18 in Manhattan, Baldessari did a piece about such interplay. He bounced a rubber ball time and time again, and each time had a pal photograph it in the air, keeping it, if possible, in the center of the frame. The ball, of course, is frozen in the photographs. It is the shifting of the framing edge, and of the background too, that gives these pictures their characteristically Baldessarian aura of surprise.

That we edit as we look -- that we keep the ball in center frame, paying small attention to the bouncing of the background -- is one of those small themes that keeps prodding Baldessari toward new works of art. What happens when the frame changes? And need it be rectangular? In 1981 Baldessari took an old movie still of a Frank Buck-like white hunter holding up a python. He then cut out the snake and employed the resulting shape -- Freudians might read it as testicles-and-phallus, or perhaps as a bra -- as a kind of viewfinder through which to look afresh at other images.

"That piece," he says, "grew out of my increasing frustration with the square and the rectangular." "Shape Derived From Subject (Snake): Used as a Framing Device to Produce New Photographs," with its imposed recollections of sexiness and slitherings, is among the strangest, and yet completely obvious, series in the show.

The oldest work on view is dated 1967. It's based on one of those familiar art lessons taught all beginning photographers: Never pose your subject in front of a tree. If you do, it will look like the tree is growing out of his head. Baldessari did. And indeed, it does. Underneath his self-portrait-with-palm-tree he inscribed the one word "Wrong."

Baldessari's influence, it has to be admitted, has not turned out to be entirely benign. Younger text-as-image artists, and those legions who "appropriate" photos from the media bank, have been busily producing much of the most coy, and much of the most arrogant, art of recent years. Baldessari is, unfortunately, one of those innovators -- like Mies van der Rohe, for instance, or Le Corbusier -- whose followers have showered us with the meretricious. That's a cross he has to bear.

Baldessari's gathered photographs, picked for heartfelt reasons, build stories in your mind. David Salle's don't. (Salle's clashing images -- say, a cartoon duck painted on a crotch shot -- seem designed to merely baffle. He who tries to read the missing linkages between them ends up thinking he's a dummy.) Baldessari's use of language tends to prod new understanding, while most newer text-as-image art -- Jenny Holzer's, for example -- is instead content to blend pompous presentation with poetry that's second-rate. Most giant glossy photographs -- given us of late as "advanced" works of art -- revel in their emptiness, and leave us feeling hollow. Baldessari's photo works are more touching, and more humorous, and more serious too. They are never wan.

He says, "I'm a little bit like a detective writer. I may lead you down a lot of false alleys, but I don't desert you."

The piece he calls "Heel" (1986), with its images of wounds -- a hiker's blistered feet, a thorn in Lassie's paw, a blacksmith gouging at a horse's hoof, and a wandering red line that links the people in a crowd -- is a picture about healing.

The series "Goodbye to Boats (Sailing Out)" is about healing too. It's a long sequence of photographs taken as the artist waves goodbye to boats sailing out to sea. It is based upon a photograph taken in his childhood -- a snapshot of his Italian-born father waving at the ship that took the artist's Danish-born mother off to Europe. "The pain and anxiety of the act," Baldessari's said, "is counterbalanced by repeating it endlessly, perhaps obliterating the sadness." What happens to a poignant act, or a poignant image, when it is repeated time and time again is a frequent subject of his art.

There is something in his work -- perhaps the sharpness of its shadows, or the way that it combines a willingness to wing it and a pleasure in the new with an inchoate nostalgia, or its devotion to the movies -- that feels peculiarly Californian.

Californian too is the sunniness that shines beyond his knife-cut shapes and conceptual austerities.

Baldessari's touring retrospective was organized by the Museum of Contemporary Art, Los Angeles. It is accompanied by a useful, jargon-free, anecdote-filled catalogue written by Coosje van Bruggen (a writer who, it seems, knows well how artists think: She happens to be married to Claes Oldenburg.) The show, already seen in Los Angeles and San Francisco, will travel to the Walker Art Center in Minneapolis, the Whitney Museum of American Art in Manhattan, and the Museum of Contemporary Art in Montreal, after closing at the Hirshhorn on Jan. 6.