Private Law Theory

ABSTRACT
When contract law invokes a reasonableness standard, whose standard applies – and what kind? Doctrine prescribes external benchmarks – industry custom, community expectations – rather than individual moral judgment. Two pre-registered experiments (N=2,342) test which benchmark laypeople apply across twenty-five contractual scenarios. Personal injunctive norms – what individuals believe one ought to do – most closely track reasonableness judgments across scenarios, demographic groups, and five framings. Legal framing, unexpectedly, appeared to deepen rather than reduce this personal-norm dominance. Conduct conforming to trade custom or community expectations may nonetheless be judged unreasonable by jurors’ own moral standards-reintroducing the uncertainty the objective standard was designed to eliminate.

Leszczyńska, Monika, The Egocentric Reasonable Person: Whose Norms Decide what is Reasonable in Contract Law? (June 1, 2026), Texas A&M University School of Law Legal Studies Research Paper.