In art as in philosophy, Zen revels in contradiction. The picture of an ant running endlessly round a grindstone is a comment on futility. A priest, on the brink of spiritual discovery, is not in elegant robes or mystic postures but wearing a battered straw raincoat, resting on a walking stick.

These days, the great devotional paintings of Christianity mostly raise a yawn. Their symbolism and scriptural references are obscure. So, quite apart from being extremely attractive splashes of black ink on white paper, the wit of Zen art may be a revelation. It shows how religious art can bypass the rational part of brain, and cut straight to our intuition. Even more surprising, it can even make us laugh.

"It's powerful, direct and honest," said the American collector Dr. Kurt Gitter, when asked about the appeal of Zen art. Ninety-eight works from his collection form the core of the exhibition at Shibuya's Shoto Museum.