Ever since the Wednesbury decision in 1947 (Associated Provincial Picture Houses Ltd v Wednesbury Corporation [1948] 1 KB 223) courts and public law scholars in the United Kingdom (UK) have been struggling to comprehend the meaning of ‘reasonableness’ and its relation to ‘proportionality’. The main purpose of this article is to promote conceptual clarity in UK public law by describing the nature of reasonableness and proportionality as grounds of judicial review and by highlighting the overlooked similarities and differences between them.The main arguments of this article are that: (i) reasonableness is, in essence, an exercise in balancing and weighing; (ii) proportionality adds very little to the existing grounds of judicial review in UK public law; (iii) this addition is not necessarily focused on the administrative weighing and balancing process; and (iv) since proportionality adds very little to the existing grounds of judicial review, there is no conceptual or normative reason to prevent having proportionality as a general ground of judicial review in UK public law.

中文翻译：

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英国公法中的异卵双胞胎：合理性和比例性

自从温斯伯里1947 年的决定（Associated Provincial Picture Houses Ltd v Wednesbury Corporation[1948] 1 KB 223）英国（UK）的法院和公法学者一直在努力理解“合理性”的含义及其与“比例性”的关系。本文的主要目的是通过将合理性和相称性的性质描述为司法审查的依据，并强调它们之间被忽视的异同，从而促进英国公法的概念清晰。本文的主要论点是：（i ) 合理性实质上是一种平衡和权衡的练习；(ii) 相称性对英国公法中现有的司法审查依据几乎没有增加；(iii) 这一新增内容不一定侧重于行政权衡和平衡过程；(iv) 由于相称性对现有司法审查的依据几乎没有增加，