The True Meaning of Rationality as a Distinct Ground of Judicial Review in United Kingdom Public Law

Abstract

Ever since theWednesburydecision in 1947, United Kingdom public law has been applying the concepts of ‘rationality’ and ‘reasonableness’ indistinguishably. Rationality has also been used as a ‘mega-ground of judicial review’, covering many other, distinct grounds of review. The main purpose of this article is to promote conceptual clarity in UK public law by highlighting the overlooked differences between reasonableness and rationality, indicating the nature of rationality as a distinct ground of judicial review and explaining why it should not be used as a mega-ground of review. It is argued that (i) reasonableness is in its essence a balancing and weighing test; (ii) the most accurate way of understanding rationality review in public law is to perceive it as ‘instrumental rationality’ or as a ‘suitability test’ which reviews the logical and causal connection between means and end; (iii) this ‘instrumental’ perception of rationality is already applied in UK public law as part of the proportionality test; (iv) rationality, unlike reasonableness, is not a weighing and balancing test; thus it is wrong to use the concepts of ‘reasonableness review’ and ‘rationality review’ indistinguishably; and (v) it is conceptually wrong and confusing to use rationality as a ‘mega-ground of review’.