In this elegant critique, Amartya Sen argues that a closer contact between welfare economics and modern ethical studies can substantively enrich and benefit both disciplines.He argues further that even predictive and descriptive economics can be helped by making more room for welfare economic considerations in the explanation of behavior, especially in production relations, which inevitably involve problems of cooperation as well as conflict. The concept of rationality of behaviour is thoroughly proved in this context, with particular attention paid to social interdependence and internal tensions within consequentialist reasoning. In developing his general theme, Sen also investigates some related matters: the misinterpretation of Adam Smith's views on the role of self-seeking: the plausibility of an objectivist approach that attaches importance to subjective evaluations: and the admissibility of incompleteness and of 'inconsistencies' in the form of overcompleteness in rational evaluation. Sen also explores the role and importance of freedom in assessing well-being as well as choice. Sen's contributions to economics and ethics have greatly strengthened the theoretical bases of both disciplines: this appraisal of the connections between the two subjects and their possible development will be welcomed for the clarity and depth it contributes to the debate. These essays are based on the Royer Lectures delivered at the University of California, Berkeley.