It is a matter of some difficulty for the English lawyer to predict the effect of a misapprehension upon the formation of a contract. The common law doctrine of mistake is a confused one, with contradictory theoretical underpinnings and seemingly irreconcilable cases. This book explains the common law doctrine through an examination of the historical development of the doctrine in English law. Beginning with an overview of contractual mistakes in Roman law, the book examines how theories of mistake were received at various points into English contract law from Roman and civil law sources. These transplants, made for pragmatic rather than principled reasons, combined in an uneasy manner with the pre-existing English contract law. The book also examines the substantive changes brought about in contractual mistake by the Judicature Act 1873 and the fusion of law and equity. Through its historical examination of mistake in contract law, the book provides not only insights into the nature of innovation and continuity within the common law but also the fate of legal transplants.

1. Introduction
2. Contractual Mistake in Roman Law: From Justinian to the Natural Lawyers
The Law of the Romans
Roman Contract Law
Roman Contract Law and Mistake
Mistakes as to the Identity of a Contracting party: Error in persona
Mistakes as to the Price to be Paid: Error in pretio
Mistakes as to the Subject Matter of the Contract
Medieval Roman Law
3. Contractual Mistake in English Law: Mistake in Equity before 1875
The Jurisdiction and Procedures of Chancery
Reasons for the Intervention of Equity
An Unconscientious Advantage Obtained by Mistake
Agreement did not Conform to Parties' Intentions
Instances Short of Fraud
Protection of a Weaker Party
The Limits of Equitable Intervention
Forms of Equitable Relief for Mistake
Rectification
Specific Performance
Rescission
Conclusions
4. The Lack of Contractual Mistake at Common Law and the Nineteenth-century Transformation of Procedure
Pleading
Equitable Defences
Evidence and the Pre-trial Discovery of Facts
Pre-trial Discovery
Witnesses
Matters of Law rather than Fact
Conclusions
5. Pothier and the Development of Mistake in English Contract Law
Pothier and the Traité des Obligations
Pothier and English Contract Law
Early Contract Treatise Writers
Colebrooke and Contract Law
Macpherson and the Indian Contract Act 1872
Leake: The First Scientific Treatise Writer of Contract Law
Judah Benjamin-The Living Transplant
Conclusions
6. Von Savigny and the Development of Mistake in English Contract Law
Von Savigny and German Legal Development
Von Savigny and Contract
Von Savigny and Mistake
Sir Frederick Pollock
Pollock's Principles of Contract
Pollock as Will Theorist
Pollock and Mistake
The Changes in Pollock's Principles
Sir William Anson and the Principles of the English Law of Contract
Anson and Mistake
Anson Modifies his Treatment of Mistake
Conclusions
7. The Creation of Contractual Mistake in Nineteenth-century Common Law
An Absence of Subject Matter: Couturier v Hastie (1856)
Mistake which Prevents Agreement-Raffles v Wichelhaus (1864)
Mistake as to a Quality of the Subject Matter-Kennedy v The Panama, New Zealand, and Australian Royal Mail Company (Limited) (1867)
Unilateral Mistake rarely renders a Contract Void-Smith v Hughes (1871)
Conclusions
8. Mistake of Identity
An Absence of Mistake of Identity in English Law
Identity Frauds: Criminal Law and the Law of Obligations
Hardman v Booth: A Turning Point
Cundy v Lindsay: The Beginning of Mistake of Identity
The Treatise Writers and the Development of Mistake of Identity
New Legislation and a Changed Judicial Approach
Conclusions
9. Mistake after Fusion
The Judicature Act 1873
Equitable Mistake in the Chancery Division of the High Court
The Impact of Procedural Unity upon Substantive Law
Reform and Perform
The Growing Necessity for the Mistake to be Bilateral
The Increasing Rigidity of Equitable Relief
Substantive Fusion of Mistake
A Reduced Ambit for Mistake in Equity
Common Law Mistake in the High Court
The Importance of Bell v Lever Brothers
The Court of Appeal
The House of Lords
The Importance of Solle v Butcher
Conclusions
10. Summary and Conclusions
Summary
Conclusions
Common Law Legal Development
Transplants
Contractual Mistake in Modern law

“MacMillan has produced a stimulating and, at times refreshing account of mistake [which] will be of interest to any modern lawyers and law students curious to know what caused all the confusion in the first place.” –  Warren Swain, The Edinburgh Law Review, Volume 15, Issue 2

“...a fascinating insight into the background of current difficulties for anyone interested in contract law.” –  Duncan Sheehan, Restitution Law Review

“...clearly of value for those interested in contract and commercial law, but it also provides much to think about for those who are interested in the history and development of the law in general, and the interactions between different legal systems specifically.” –  Dr Sean Thomas, The Journal of Business Law, Issue 7

“The author has ... meticulously researched each of the principal judicial pronouncements that has assisted in the development and understanding of the doctrine of mistake...a useful historical analysis.” –  Anthony Lo Surdo, Australian Banking and Finance Law Bulletin, Volume 26, Number 5

“...this is a legal history book. It will clearly be of interest to legal historians and to academics who want to know how the law developed to its current state.” –  David Capper, Canadian Business Law Journal, Volume 49

“...there can be no denying that [MacMillan] has produced a very worthwhile and thorough book. It is impressively wide-ranging, carefully researched, and brings to light previously overlooked evidence about the development of mistake in the English law of contract. As a result of it, our understanding of this difficult doctrine has taken a big step forward.” –  Paul Mitchell, The Journal of Legal History 32: 1