Reasonableness

The concept of reasonableness has two related meanings in law and political theory:

1. As a legal norm, it is used "for the assessment of such matters as actions, decisions, and persons, rules and institutions, [and] also arguments and judgments."^[1]
2. As a regulative idea, it "requires... that all factors that might be relevant in answering a practical question be considered and... that they be assembled in a correct relation to each other in order to justify [a judgement]."^[1]

Reasonableness should not be conflated with rationality.^[1]

Reasonableness has been discussed by political thinkers such as John Rawls (in his 1993 Political Liberalism),^[2][3][1] T. M. Scanlon,^[2] Brian Barry^[2] and Georg Henrik von Wright.^[1]

The notion of "reasonableness" is omnipresent in European law, and has also affected "international treaties and general customs".^[4] Examples of its use can be found in canon and medieval law, suggesting roots going back to Ancient Rome.^[4]

Standards and doctrines requiring reasonableness include:

• Reasonability
• Reasonable accommodation
• Reasonable act^[5]
• Reasonable appearance of danger^[5]
• Reasonable care^[6]
• Reasonable cause^[5] or reasonable and probable cause^[7]
• Reasonable and competent support^[5]
• Reasonable creature^[5]
• Reasonable danger^[5]
• Reasonable diligence^[8]
• Reasonable doubt
• Reasonable expectation^[5] (Legitimate expectation is sometimes called reasonable expectation.)^[9]
• Reasonable facilities^[5][7]
• Reasonable fitness^[5]
• Reasonable mind^[5]
• Reasonable and non-discriminatory licensing
• Reasonable person or reasonable man^[5]
• Reasonable portion^[5]
• Reasonable possibility^[5]
• Reasonably practicable^[5]
• Reasonable and probable damage^[5]
• Reasonable and probable grounds
• Reasonable provocation^[5]
• Reasonable prudence^[5]
• Reasonable question^[5]
• Reasonable rates^[5]
• Reasonable regulation^[5]
• Reasonable right of way^[5]
• Reasonable skill^[10]
• Reasonable suspicion
• Reasonable time^[11][7]
• Reasonable use^[5]
• Reasonable wear and tear excepted^[5]
• Subjective and objective standard of reasonableness

In constitutional and administrative law, reasonableness is a lens through which courts examine the constitutionality or lawfulness of legislation and regulation.^[12][13][14] According to Paul Craig, it is "concerned with review of the weight and balance accorded by the primary decision-maker to factors that have been or can be deemed relevant in pursuit of a prima facie allowable purpose".^[15]

Examples of reasonableness standards in common law jurisdictions include:

• Reasonableness simpliciter and patent unreasonableness (repealed in 2008) in Canadian law^[16]
• Wednesbury unreasonableness in English law
• Wednesbury unreasonableness in Singaporean law

• Reasonableness cause in Israeli law (עילת הסבירות)
• Reasonableness in South African administrative law

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Reasonability is a legal term. The scale of reasonability represents a quintessential element of modern judicial systems and is particularly important in the context of international disputes and conflicts of laws issues. The concept is founded on the notion that all parties should be held to a reasonable standard of conduct^{[citation needed]} and has become embedded in a number of international conventions such as the UNIDROIT principles^[17] and the CISG.^[18]

The concept of reasonability is applicable to Roman law.^[19]

• Reason

• Bongiovanni, Giorgio; Sartor, Giovanni; Valentini, Chiara (2009). Reasonableness and law. Law and philosophy library. Dordrecht New York: Springer. ISBN 978-1-4020-8500-0.
• Hevia, Martín (2013). Reasonableness and responsibility: a theory of contract law. Law and philosophy library. Dordrecht: Springer. ISBN 978-94-007-4604-6.
• Vadi, Valentina (2018). Proportionality, reasonableness and standards of review in international investment law and arbitration. Elgar international investment law. Cheltenham, UK Northampton, MA, USA: Edward Elgar Publishing. ISBN 978-1-78536-858-5.
• Volpi, Franco, ed. (2003). Reasonableness and interpretation. Ars interpretandi. Münster: LIT Verlag Münster. ISBN 978-3-8258-6638-9.
• Young, Shaun, ed. (2014). Reasonableness in Liberal Political Philosophy. Taylor & Francis. ISBN 9781317983750.
• Dindjer, Hasan (2020). A theory of reasonableness in administrative law (Ph.D. thesis). University of Oxford.

• Boettcher, James W. (2004). "What is reasonableness?". Philosophy & Social Criticism. 30 (5–6): 597–621. doi:10.1177/0191453704045756. ISSN 0191-4537. S2CID 146271626.
• Clancy, Thomas K. (2004). "The Fourth Amendment's Concept of Reasonableness". Utah Law Review (4): 277. SSRN 1565797.
• Craig, Paul (2013). "The Nature of Reasonableness Review". Current Legal Problems. 66 (1): 131–167. doi:10.1093/clp/cut010.
• Garrett, Brandon L. (2017). "Constitutional Reasonableness". Minnesota Law Review. 102: 61–126.
• Mangini, Michele (2018). "Toward a theory of reasonableness". Ratio Juris. 31 (2): 208–230. doi:10.1111/raju.12205.
• Zipursky, Benjamin C. (2015). "Reasonableness in and out of Negligence Law". University of Pennsylvania Law Review. 163 (7): 2131–2170.
• Sokol, Sam (2023-01-19). "Israel's 'Reasonableness' Standard Is in the News. But What Is It and Why Do We Need It?". Haaretz. Retrieved 2023-07-13.