unreasonableness

Unreasonableness is a quality of judgment or action characterized by a lack of adequate justification, failure to consider relevant factors, or results that appear irrational given the surrounding facts. In ordinary usage it marks decisions or demands that seem excessive, arbitrary, or out of step with the relevant norms of fairness and practicality. The term does not simply mean being mistaken; it denotes a failure to rationally support conclusions or policies.

In law, unreasonableness is a ground for judicial review of administrative decisions. The phrase often signals that a decision is irrational or illogical in a way that no reasonable authority could have adopted it. The classic standard, known as Wednesbury unreasonableness, requires that a decision be so unreasonable that it defies justification. In many jurisdictions proportionality has become an alternative or additional test, demanding that limits on rights be necessary and suitably balanced rather than merely irrational.

In everyday contexts, unreasonableness is used to critique policies, rules, or demands as disproportionate, inconsistent, or lacking legitimate purpose. It can reflect cognitive biases, emotional pressures, or information gaps that hinder sound judgment. Ethical discussions may treat unreasonableness as a failure of fair deliberation or respect for others' interests.

Philosophically, unreasonableness relates to theories of rationality and decision-making. It is contrasted with rational choice and coherence, though real-world decision making often involves bounded rationality, where limits on time, knowledge, or computation produce apparently unreasonable outcomes that may still have practical value.

Related concepts include rationality, irrationality, the reasonable person standard, abuse of discretion, proportionality, and bounded rationality.