Research Paper Number


Subsequently published in the Osgoode Hall Law Journal.

Document Type


Publication Date



mistake in assumption; contract law; mistake of fact; misrepresentation; frustration; unjust enrichment; equity; mutual mistake


Mistake raises several important and difficult questions for contract law. The question addressed here is, when is it an excuse from contractual obligation that a contract has been made under the influence of a mistake of fact? Posed in this form, the question invites attention to aspects of contract law not usually considered in relation to each other, particularly misrepresentation, frustration, and more generally, unjust enrichment, all areas in which Professor McCamus has written extensively. This article brings these areas together with the object of throwing useful light on each of them, both from the point of view of understanding the legal past, and from the point of view of proposing appropriate rules for the future.