Most people know the famous riddle, "What is the sound of one hand clapping?" Many are also aware that it is connected with Zen Buddhism, and some will even know that it is a famous koan by the 18th-century monk Hakuin.

A koan, of course, is a paradoxical parable or query used in Zen Buddhism to elicit enlightenment. One of the interesting aspects of this famous koan is that it raises the question of what the other hand — presumably that of Hakuin himself — is doing, which is appropriate, because Hakuin more than perhaps any other famous Zen master had a dual approach to Buddhism.

On the one hand there was his meditation and thought, expressed in his koans and other writings, while on the other there was his art, now the subject of "Hakuin: The Hidden Messages of Zen Art" at Bunkamura, The Museum, in Tokyo.