Cornell Law Review

Though the notion of reasonableness dominates Anglo- American law, its meaning has been clouded by traditional conceptual analysis. This Essay argues that greater clarity can be gained by taking a scientific approach to the subject, exposing the natural foundations beneath the concept’s varied interpretations.

Reasonable legal minds agree that reasonableness is one of the foundational concepts of American law, infiltrating everything from administrative, corporate, and constitutional law to crimes, torts, and contracts.^{11. See Brandon L. Garrett, Constitutional Reasonableness, 102 MINN. L. REV. 61, 69–70 (2017) (recounting the concept’s significance and use within multiple legal fields); Frédéric G. Sourgens, Reason and Reasonableness: The Necessary Diversity of the Common Law, 67 ME. L. REV. 73, 74–75 (2014) (same).} Yet the concept’s importance and prevalence have not necessarily bred clarity. In fact, a recent flurry of analytic interpretations has only clouded the term’s meaning.^{22. The latest entry appeared just last year in the Yale Law Journal Forum. See Alan Z. Rozenshtein, Fourth Amendment Reasonableness After Carpenter, 128 YALE L.J.F. 943 (2019).} While some scholars say reasonableness is a prescriptive standard,^{33. See Alan D. Miller & Ronen Perry, The Reasonable Person, 87 N.Y.U. L. REV. 323, 326 (2012) (“We put forward and defend the argument that normative definitions [of reasonableness] are categorically preferable to positive definitions because the latter are logically unacceptable.”).} others believe it describes existing community values,^{44. See Kevin P. Tobia, How People Judge What is Reasonable, 70 ALA. L. REV. 293, 299–300 (2018) (describing this view of reasonableness as a search for the statistically average characteristics of people within a community).} and still others see it as a combination of the two.^{55. See id. at 296 (arguing that “[r]easonableness is best understood as a hybrid notion that is partly statistical and partly prescriptive”).} This split is deepened by disagreements over the concept’s normative basis. Indeed, the latest proposals ground reasonableness in a wide variety of ideals, including utilitarianism, economic efficiency, fairness, deontological respect, pragmatic rationalism, formalism, mutuality, and aretaic virtue.^{66. See Sourgens, supra note 1, at 80–105 (discussing utilitarian, pragmatic, and formalist paradigms of reasonableness); Benjamin C. Zipursky, Reasonableness In and Out of Negligence Law, 163 U. PA. L. REV. 2131, 2160–65 (2015) (proposing a theory of reasonableness as mutuality); Lawrence B. Solum, Legal Theory Lexicon: The Reasonable Person, LEGAL THEORY BLOG (Apr. 21, 2019), https://lsolum.typepad.com/legaltheory/2019/04/legal-theory-lexicon-the- reasonable-person.html [https://perma.cc/3VSX-SGJB] (addressing efficiency, fairness, deontological, and virtue-based notions of reasonableness).}

Since reasonableness effectively serves as law’s conscience, doubts about its essence are an obvious cause for concern. But the impasse also puts legal theory in a serious predicament. If reasonableness means different things to different people—or, at least, different things in different legal contexts—then there is little point to searching for a common unifying principle. Even if such a principle exists, traditional conceptual analysis has struggled to discover it. As jurisprudence maven Lawrence Solum recently observed, legal philosophy’s exhaustive polemic on reasonableness eventually just “runs out of gas.”^{77. Solum, supra note 6.}

Yet the problem with these approaches is not a lack of analytic rigor. Rather, it is an absence of critical facts. What is missing from the discussion of reasonableness, I argue, is a basic understanding of human nature. Because science informs that inquiry, this Essay explores the biological origins of reasonableness by probing three of its key connotations: sensibleness, fairness, and moderation. The first meaning evokes mankind’s integrated cognitive faculties; the second addresses humanity’s reflexive values; and the third entails the coordinative processes animating human decision-making. Together, these attributes suggest that reasonableness is not an abstract, static, or monolithic ideal; rather, it is an organic, dynamic, and systemic phenomenon for satisfying our natural urge for homeostasis.

To read more, click here: The Nature of Reasonableness.