This paper introduces the concept of ordient for binary relations (preferences), a relative of the concept of gradient for functions (utilities). The main motivation for this study is to replace the ordering at the center stage of economic analysis, rather than its representation, if it exists....

This note studies the problem of implementing social choice correspondences in environments where individuals have doubts about the rationality of their opponents. We postulate the concept of "-minimax regret as our solution concept and show that social choice correspondences that are Maskin...