The death of Amos Tversky on June 2, 1996, brought an end to the distinguished career of one of the pioneers of behavioral finance. Tversky documented a number of systematic errors in judgment to which humans are prone—cognitive illusions being one of the best known. Tversky's work fit the pattern of Nobel Prize winners in economics in challenging conventional wisdom, being based on “simple” ideas, and spawning copious research by others.