The concept of "madness" is not one with which psychologists, psychiatrists, or neurologists, of the 21st century have any dealings. Musicians, yes ... see above. Philosophers also still talk about madness, because philosophy is uniquely keyed to its past, still arguing cases litigated by Plato or Philo or Lao-Tsu. Anyway: Justin Garson, a professor of philosophy at CUNY, has written a book simply titled Madness: A Philosophical Exploration . Garson's point is that in ancient times there were two very different views of what the ancients called madness. There was madness as dysfunction, or madness as strategy. When medieval Christian philosophers addressed the point, they tended to combine both ideas. Madness could serve as an earthly purgatory, both punishing and improving. It is early modern thinkers, from Locke to Kant, whom Garson credits/blames for the dominance of madness-as-dysfunction in our own time. A review devoted largely to summari...