rationality

Rationality generally denotes the quality of being reasonable or of acting in accordance with sound reasoning and evidence. In philosophy and cognitive science, it is often understood as the alignment of beliefs and actions with logic, probability, and defined goals. The term covers both the correctness of reasons for belief and the effectiveness of decisions given one’s objectives.

Two common strands of rationality are instrumental rationality and epistemic rationality. Instrumental rationality concerns selecting the means that best achieve one’s ends, given constraints and information. Epistemic rationality concerns the degree to which beliefs are formed and revised in light of evidence, avoiding known logical or evidential biases. In decision theory, rationality is frequently formalized through Bayesian and utility-maximization frameworks, emphasizing coherent beliefs and consistent preference orderings.

Bounded rationality, proposed by Herbert Simon, acknowledges cognitive limits and environmental complexity. People use heuristics and satisficing rather than exhaustive optimization, which can yield good enough outcomes but may also introduce systematic errors. Related ideas include dual-process theories, which distinguish fast, intuitive thinking from deliberate, effortful reasoning.

Rationality is debated as a normative standard—how people ought to think and decide—and as a descriptive phenomenon—how people actually think and decide. Critics note that rationality is culturally and contextually dependent, that it may privilege certain forms of reasoning, and that models may overlook values, social constraints, and practical uncertainties. Despite disagreements, rationality remains a central concept in logic, economics, science, and philosophy.