Choosing and Describing: Sen and the Irrelevance of Independence Alternatives

Abstract

Amartya Sen argues that it is not, after all, irrational to reverse preferences when your choices are amplified by an ‘irrelevant’ alternative. He offers examples such as the agent who always picks the next-to-largest piece of cake. Given a choice between a larger and smaller piece, I will prefer the smaller one. But when a third and largest piece in added to my alternatives, I will now prefer the formerly largest piece over the smallest piece. This violates ‘contraction consistency’: a third alternative should not have made any difference in my preferences regarding the first two. Such examples are shown to rely on descriptions which omit features crucial to choice. These features, and all identifying features relevant to my decision, should be included in the descriptions of the alternatives. An adequate description does not smuggle norms into the overt act of choice, but it does include the non-normative characteristics without which my decision-rules, if any, cannot be applied. When alternatives are adequately described, Sen’s inconsistencies disappear. The result is a clearer and more resillent, but also less aggressive notion of behavioral consistency.