This incisive critique of standard a priori welfare economics provides a rigorous analysis of concepts such as Paretian optimality, externalities, economic efficiency, technological efficiency, second best, the social welfare function, and welfare criteria. Nath illustrates his central theme in the specific fields of public enterprise pricing, international trade, and economic development. "Convincing as well as courageous ... his book should command wide attention among economists." British Book News. "The implications of Mr. Nath"s work are immensely important." Times Literary Supplement