This unique study investigates a theory of international arbitration culture alongside the publicly available arbitral awards, in order to make predictions about the contract law principles that international arbitrators are likely to favour. Drawing on interviews with prestigious practitioners in a range of jurisdictions, as well as case studies, conference papers, and unpublished awards, it presents a comparative analysis of arbitral and judicial responses to contractual principles. Part I presents the divergence in outcomes between national court litigation and international arbitration in relation to substantive law determinations, conducting in-depth case studies in two areas: the suspension of performance in response to non-performance, and the admissibility of extrinsic evidence to interpret contracts. Part II accounts for the conclusions of Part I with a comprehensive theory of arbitral decision-making, grounded in evidence gathered first-hand from arbitrators themselves.