Amartya Sen is probably best known for his work on famine, human development and welfare economics. He is one of the few modern academics who has commanded much respect and recognition from all corners of the intellectual spectrum. His work simultaneously embraces social choice theory and economic development, thus breaking the barrier between mathematized ?high theory? and ?real world? economics for which he was awarded the Nobel Prize in 1998. His reputation is mostly based on two other key works: Collective Choice and Social Welfare (1970) and On Economic Inequality (1973). The first looks at the question of whether it is possible to base some kind of rational social choice entirely on the preference orderings of individuals. The second examines and evaluates virtually every measure that has ever been proposed to quantify the degree of inequality of the distribution of income, showing that all of them involve hidden and sometimes surprising value judgements. Gathering the key assessments on Amartya Sen together, this four-volume collection will be an invaluable resource for both reference purposes and as a contribution to the study of Amartya Sen.