The importance of incompleteness

Kotaro Suzumura can be seen as the most complete social choice theorist the subject has ever had. No area of social choice has failed to benefit from Suzumura's penetrating analyses. Among the many important contributions made by Suzumura is the use of the idea of incompleteness of evaluation in his analysis of consistency, particularly in the form of what has come to be called “Suzumura consistency”. In this paper I explore the need for allowing – and incorporating – incompleteness of preferences in choice theory in general and social choice in particular. This is followed by a number of critical enquiries. Why is incompleteness important? How does it arise as an essential part of rational reflections? What are its implications (i) for prudential decisions, and (ii) for ethical judgments? Finally, how should making room for incompleteness influence theories of justice?