STEPHEN TOULMIN George Santayana used to insist that those who are ignorant of the history of thought are doomed to re-enact it. To this we can add a corollary: that those who are ignorant of the context of ideas are doom ed to misunderstand them. In a few self-contained fields such as pure mathematics, concepts and conceptual systems can perhaps be de tached from their historico-cultural situations; so that (for instance) a self-taught Ramanujan, living alone in India, mastered number theory to a point at which he could make major contributions to European mathematics. But elsewhere the...