FEW THINGS MADE by man are as harmless as his paintings.Bad buildings cramp your living, bad movies waste your money, bad books waste your time, but bad paintings aren't that bad. They usually instruct, frequent amuse, and if you cannot bear them, they are easy to avoid. Simply close your eyes.

Do not get me wrong. Much art is meretricious, insincere, pretentious. Frenchman Bernard Buffet, Ernst Trova (of the "Falling Men"), Dali, that old hustler, and Keene of the big eyes, seem to know no shame. Still, they do not harm. Those who buy their pictures spend the cash on purpose. Whay they see is what they get.

But the art-historical star system frequently misleads. The big name on the label is no guarantee of quality, and not all works made by masters qualify as masterworks. I recall a Cezanne landscape, once owned by Armand Hammer, that struct me when I saw it here at the Smithsonian Institution as a thoroughly botched job. (Cezanne, incidentally, tended to agree) Gauguin's "The invocation," now in the collection of the National Gallery of Art, is another loser, Van Gogh's "Girl in White," which also is on view there, seems, at least to me, a weak and awkward picture. Good cooks sometimes burn the roast. Good painters sometimes have bad days.

Degas had them rarely. Renoir had them often. Even at his best, which is very good indeed, Renoir is sometimes gooey, repetitious, sentimental. Look, for instance, at the Phillips Collection's "Luncheon of the Boating party," a painting Duncan Phillips called "one of the great pictures of the world."

But greatness, goodness, badness are, of course, determined by one's point of view. On a wet gray winter day, one might see that sunny Renoir and agree with Phillips. Renoir's colors are delightful, his air is full of joy, the central still life sparkles, and the people in the painting all are having fun. But look twice at their faces. Suppose you've just communed with the somber, knowing eyes of a self-portrait by Rembrandt. Suddenly those women, partying in Paris, look vacuous and bland. Their individuality is minimal. All we see is youth, pink skin, pursed lips, adoring glances. A spectator in search of bright good times and happy painting might applaud this splendid Renoir, while another who responds to deeply moving portraiture might find it empty, bad. The painting, like some operas, is both sublime and meretricious.

The good and bad in painting, often coexist, for all paintings are in some way allied.Even the worst - a child's scrawled drawing, a cheap motel-room landscape, the colorful abstraction, empty as canned laughter, that decorates the set of the TV show - may call the mind to art.

The child's painting, crude as it may be, shows us something of his spirit, something of the time. Is such expression "bad"? A crummy motel landscape may document the decadence of the Barbizon tradition, or the influence of Andrew Wyeth. The abstraction on the tube may show a debt to Albers, to de Kooning or to Stella, and may help explain their fame.

"Art," said wise Marcel Duchamp, "may be bad, good or indifferent, but whatever adjective is used, we must call it art, and bad art is still art in the same way that a bad emotion is still an emotion."