Social choice

Social choice theory is the branch of economics concerned with the relationships between individual values, preferences and rights and collective decision making and evaluation. Social choice theory therefore provides connections between the formal analysis of rational choice, the debate on political process, and ethics. A central theme in social choice theory has been the aggregation of individual preferences into either a social decision rule or a social evaluation rule. The most famous result in social choice theory – Arrow’s impossibility theorem – is that such aggregation is impossible if individual preferences are conceived as ordinal in nature, and if the aggregation procedure is to satisfy certain apparently reasonable conditions. This result implies that neither a voting system nor a system of moral evaluation can be found that satisfies all of the required conditions. Further impossibility theorems arise from attempts to model the role of individual rights.

Much of social choice theory is concerned with interpreting, extending and questioning these impossibility theorems in a variety of contexts. This discussion has generated an extensive interchange at the margins of economics and ethics on topics such as the commensurability of values and the relationship between morality and rationality.