Epistemic authority and Wednesbury unreasonableness

Wednesbury unreasonableness is a central feature of English administrative law, but its theoretical foundations remain unclear. The three leading explanations – Parliament’s intent, the rule of law, and a culture of justification – cannot sufficiently explain why courts should scrutinise the executive’s weighing and balancing of relevant factors but should not themselves weigh and balance those factors. Here, I reconceptualise Wednesbury using Linda Zagzebski’s definition of an epistemic authority: one whose ability to identify and weigh evidence in her epistemic domain is superior to laypersons’, making her consciously-formed beliefs more likely to be true and thus deserving of pre-emptive force. Understanding Wednesbury as policing epistemic authority provides a sufficient explanation for it – courts should accord a decisionmaker’s beliefs pre-emptive force but only if reached conscientiously – and settles boundary disputes between Wednesbury, rationality review and proportionality.