[Page 409]Irrationality refers to attitudes, beliefs, or choices of individuals or societies that are determined by something other than rational deliberation or that fail to correspond to reason. Although much of the concern with irrationality in politics relates to matters of individual psychology, deliberation—the careful assessment [Page 410]or weighing of considerations—can be understood both as a cognitive process of an individual mind and as a social process of back-and-forth communication among a group of decision makers. This means irrationality’s connections to politics are fundamental and direct as well as complex.

Whenever deliberation (individual or social) is absent, fails, breaks down, or is otherwise ineffective, irrationality is said to be present. This entry looks first at the influential argument from Western antiquity equating politics with reason. It ...