Introduction

Any principle of choice uses certain types of information and ignores others. A principle can be understood and assessed in terms of the information that it demands and the information that it “rules out” (i.e., prevents from being directly used). Principles used in social choice theory, moral philosophy, rational choice under certainty and uncertainty, and studies of actual behavior can all be interpreted and analyzed in terms of the informational constraints that they – typically implicitly – involve (Sen 1970a, b, 1979).

The philosophical foundations of informational analysis go back at least to Kant (1788) and to his discussion of the need for universalization in categorical imperatives. The need to make similar judgments in similar circumstances is a requirement that has been used in many different forms, and the domain and scope of such a requirement depend on the way “similarity” of circumstances is interpreted and the way “similarity” of judgments is required. But the “bite” of such requirements of universalization lies in the constraint that excludes discriminations based on information not included in the relevant notion of similarity of circumstances.

Informational constraints are typically used implicitly. Although it is often helpful to analyze and assess principles of choice in terms of the informational constraints they involve, these constraints are usually entailed rather than explicitly stated in the formulation of these principles.