ANIMAL, vegetable or mineral? Bigger than a breadbox? Useful or decorative?

Most people consider such distinctions only when they are trapped in a car, playing 20 questions. In a Tom Stoppard play, though, little questions about everyday things take on cosmic significance. On his stage, the minutiae of rock music and landscape gardening are perfectly acceptable sparring partners for quantum mechanics and communist ideology.

It certainly keeps things interesting. Whether he has you wondering where the literary sleuths of “Arcadia,” or how the rock-obsessed Czech dissident in “Rock ’n’ Roll” (now at the Bernard B. Jacobs Theater in Manhattan), will end up, it is clear that Mr. Stoppard loves a little mystery.

Who doesn’t? For playwright and audience alike, there is no greater moment of satisfaction than when all is revealed. “It’s so great in the theater when everyone catches up on the truth,” he said.

He would know, having for 30 years carried a portable enigma, the drop-front of which opens a surprisingly clear window into the mind of its porter. This intriguing valise looks as if it should be handcuffed to his wrist and contain enriched uranium, the Dead Sea Scrolls or a kidney. But no  it holds books, and very neatly, as he has explained countless times to curious fellow travelers.