Looking back on his confinement to Bethlem, Restoration playwright Nathaniel Lee declared: "They called me mad, and I called them mad, and damn them, they outvoted me." As Roy Porter shows in Madness: A Brief History, thinking about who qualifies as insane, what causes mental illness, and how such illness should be treated has varied wildly throughout recorded history, sometimes veering dangerously close to the arbitrariness Lee describes and often...