This collection of essays in honor of Abram Bergson pays tribute to a distinguished teacher, scholar, and friend whose intellectual vision has vivified research in the fields of welfare economics and the economics of Soviet socialism. The enormous impact that his works have had on the development of these disciplines during the last four decades is attributable not only to the innovative spirit of his scholarship, but also to its unity. The common thread tying together the disparate strands of his life's work lies in his overriding concern with the phenomenon of human welfare. Soviet economic institutions and working arrangements are of interest not simply because they exist, but because they shed light on the possibility of organizing society in a better way, a way that improves the quality of life. This possibility, however, as Bergson never tires of stressing, should not be confused with its realization. The consequences of social action are often complex and contradictory. Their appraisal depends not only on scrupulous quantification but on a lucid understanding of the factors determining economic welfare. It was one of Bergson's greatest achievements to clearly recognize at the outset that the comparative economic merit of Soviet socialism could not be assessed without the aid of a rigorously elaborated, pure theory of economic welfare. His seminal research on social welfare functions should be seen in this light, attesting to his enduring commitment to advance our scientific understanding of the determinants of human welfare.