On my office wall hangs “The Conjurer,” a painting by the 15th century Dutch artist Hieronymus Bosch. On the right side of the canvas, a conjurer holds a small ball between his fingertips. On the other side of the table a gowned spectator, bent over like a hunchback, stares idiotically at the small ball. Behind the spectator, hidden from the stares of the diverted crowd, the conjurer's accomplice is stealing the spectator's purse.

Like the spectator in Bosch's painting, the modern medical ethicist is at risk of losing something of considerable value. By focusing so closely on the little ball—the purely philosophical aspects of medicine (such as the meanings of autonomy)—the ethicist too easily ignores the broader context in which these issues arise. The combination of abstruse theorising and ignorance of practical medicine alienates the very people the ethicist is trying to help.

To be of any use to practitioners, armchair bioethics, which tends to tackle issues in a contextual vacuum, must make way for a more streetwise form of bioethics in which conceptual analysis is coupled …