Every profession is occasionally inflicted with challenges which loom large. The challenge may take the form of a book which purports to produce a fundamental revision—in economics these would include Keynes' General Theory, Hicks's Value and Capital, Samuelson's Foundations; or, in the narrower field of international economics, Meade's Trade and Welfare. Or it may be a methodological revolution. Or both. Older members of the profession may try to ignore the challenge. And some of these challenges, ignored, oblige by disappearing. Others have to be faced, sooner or later.