The Proportionality Puzzle in Contract Law: A Challenge for Private Law Theory?

This article explores the emerging use of the proportionality concept in the contract law of the Anglo-common law world, first to understand its internal logic, and secondly, to situate its invocation within private law theory. What are judges doing when they appeal to "proportionality"?, and what does this say about the ideology of adjudication? I draw insights from the use of proportionality in other domains, in particular public law, to uncover its internal rationality as a means-ends rationality review coupled with a process of balancing competing considerations, which I illustrate with reference to the illegality, penalty, and cost of cure doctrines. I argue that proportionality reflects a method of pragmatic justification, expressing an aspiration towards a structured and transparent mode of argumentation that is anti-formal and anti-ideological, focusing from the bottom-up on contextual considerations, and occupying a distinct space against existing theories in private law driven, for instance, by "top-down"? rights-based ideologies or critical and communitarian perspectives.