Art Caplan (Credit: Chris Crisman)

Round and brash, with the gravelly voice of a street fighter, Arthur Caplan looks and sounds more like a boxer than an ethi­cal philosopher. The director of the Center for Bioethics at the University of Pennsylvania, Caplan has been enormously influential in a variety of debates in modern biomedicine, from the fate of Terri Schiavo to the market for organs for transplant. He has written or coauthored more than 400 peer-reviewed articles and several books on the ethics of new medical technologies.

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