Exhibitions: A Hint, a Shadow, a Clue

"My father, methinks I see my father," quoth Prince Hamlet. Where? asked the startled Horatio. "In my mind's eye," replied the prince, with what must have been a sly smile. Today, more and more artists are devoting themselves to art that exists primarily in the mind's eye. Called "conceptual art," it usually exists in the form of a scale model, a preliminary sketch or a written description, suitable for framing. Any of these items, the artists explain, are but a hint, a shadow, a shade, a clue to the real thing, which is usually some concept so complex, so subtle,...