THE chameleon-like advice for painters is Leonardo da Vinci's. His words show how much he believed paintings should appear "real." He goes even further and advocates using mirror images as a measure of a painting's success.
But to enjoy a painting's realism, we need to be at least half aware that it is still, after all, "only a painting": rectangular, two-dimensional, made of paint. Its realism does not need to be as extreme, for example, as the hyper-realist sculpture of a 20th-century artist like American Duane Hanson. His figures elicit a classic double take because at first sight they seem exactly like people we see all around us. Only closer investigation shows we have been taken in. Even when we continue to stare at them, hoping to catch them out by discovering the ways in which they are not "realistic," we remain rather awe-struck.
Leonardo's own famous painting, the Mona Lisa, is, for all its astonishing realism, flat and two-dimensional, like most paintings. Whatever seems three-dimensional about it - the roundness of the face, the distant landscape - must, like the image we see in a flat mirror, be an illusion: an ingeniously contrived artifice of the brush. And this illusion, as E.H. Gombrich argued in his book "Art and Illusion," is partly dependent on the viewer's willingness to be convinced - or deceived - and partly the result of the artist's ability to invent a context in which an illusion has the greatest chance of working. Charles Willson Peale's "Staircase Group" is a fine example, set as it is in an actual door frame, with a real step protruding at its base.
The philosopher Plato disputed the worth of painting because it was aimed to deceive, to be deliberately not the truth. But one might contend that with painting half the point is to be fooled. It takes, we say, "imagination" to appreciate painting. And it takes a willing imagination to be taken for a ride.
The extent to which paintings fool the eye varies. Many painters have gone out of their way to emphasize the tangibility of paint texture and brush marks, making no effort to smooth out such rough traces. This deliberately belies the illusory aspect of picture-making.
BUT some painters have gone to the other extreme, doing everything they could to make paintings that trick viewers into believing they are seeing an object rather than a painting of that object.
The French came up with a phrase for this: trompe l'oeil, painting that "tricks the eye." Peale's piece of trompe l'oeil bravura, portraying two of his sons, prompted art historian Jules David Prown to write: "Trompe l'oeil paintings have enjoyed particular appeal throughout the history of American art. Perhaps this reflects the pragmatism and materialism of American life, its firm commitment to the real world."
Prown goes on to tell the story of President Washington noticing this trick painting at an exhibition and doffing his hat to it. This anecdote, meant to prove how accomplished the painting is, is a modern version of the archetypal story about deceptively real painting in the classical world. The ancient Greek painters Zeuxis and Parrhasios competed with each other. The former painted grapes so "real" that birds swooped to eat them. The second then invited the first to his studio to see a new painting. It was covered with a curtain, and Zeuxis, eager to see the work, reached out to lift it away. But the curtain was made of nothing but paint. Zeuxis, who should have known better (so the moral goes), had been taken in completely.
Intriguingly, Peale portrayed himself pulling back a curtain to reveal the gallery of the museum he founded in Philadelphia. This advertisement suggests the 18th-19th-century American knew the old Greek tale, and was consciously making his own competitive gesture: a painted man with a painted curtain revealing a painted museum. Games, games.