With the publication of his new book, The Idea of Justice, Amartya Sen announces a needed new departure in political philosophy. In effect he takes a great tradition gone stale -- social liberalism -- and suggests needed updates. In doing this with verve, he places himself in the company of great liberals of the past who argued strenuously for liberty, and against injustices: Condorcet in France, and Mary Wollstonecraft in England, who fought eloquently against slavery and for the emancipation of women; John Stuart Mill the great 19th century champion of the expansion of human capabilities; and John Maynard Keynes, the persuasive exponent of the capacity of human ingenuity to overcome economic depression.