Note: This is the first part of a series of articles on integration, or merger clauses, in contracts. The next installment is about the legal effect of merger clauses.
History of the Parol Evidence Rule
Scholars trace the origins of the parol evidence rule to the “primitive formalism which attached mystical and ceremonial effectives to the carta and the seal.” Michael B. Metzger, The Parol Evidence Rule: Promissory Estoppels’ Next Conquest? 36 Vand. L. Rev. 1383, 1386 (1983) (subscription required). The term “parol” literally means “word” and comes to us from legal French. The French term was derived from ecclesiastical Latin “parabola,” meaning “speech.” Id. Despite its ancient origins, the rule continues to significantly impact the interpretation and enforcement of modern contractual obligations.
Evidentiary rule?
Much of the early scholarship concerning the parol evidence rule appears in evidence treatises, such as James Thayer’s A Preliminary Treatise on Evidence at the Common Law (1898) and John Henry Wigmore’s A Treatise on the System of Evidence in Trials at Common Law (1905). Focusing on the evidentiary aspects of the parol evidence rule, scholars have frequently noted the “Countess of Rutland’s Case” as an early foundation for the parol evidence rule.
The Countess of Rutland’s case dates from 1604, and considered multiple, apparently inconsistent transfers of land, whereby Edward Earl of Rutland willed his property to his wife in one document and to the male heirs of his father in a second document. The Countess sought to present oral testimony from the trustees to prove that Edward actually wanted his property to go to her at his death. But the Countess was prohibited from introducing such evidence by the court. The court reasoned: “if other agreement or limitation of uses be made by writing, or by other matter as high or higher, then the last agreement shall stand; for every contract or agreement ought to be dissolved by matter of as high in nature as the first deed.” The basic idea announced in the case was that oral evidence should not be introduced to contradict or vary a written contract. It was likely important to the court that the contracts at issue were written more than twenty years prior to the decision concerning the conveyances. Consequently, there was a high likelihood (and concern at the court) of faded or inconsistent memories. The rule announced in the Countess of Rutland’s case is seen as primarily an evidentiary rule.
Scholarship viewing the parol evidence rule as a rule of evidence often notes courts’ concerns about (1) the uncertainty of memory, and (2) the danger of falsehood or perjury. For these scholars and courts, the fundamental purpose of contract interpretation is to ascertain with as much certainty as possible the intent of the parties. Seeking to find that intent, they believe written evidence is more certain and more accurate than evidence that exists in the mind of the biased party. See Joseph Urquico, Parol Evidence Rule, 5 Notre Dame L. Rev 303 (1930) (subscription required).
Substantive law.
Modern scholarship and courts, however, view the parol evidence rule as a substantive rule of contract law, not merely an evidentiary rule. First National Bank in Durant v. Honey Creek Entm’t Corp., 54 P.3d. 100, 103 (Okla. 2002) (“parol evidence rule is not a rule of evidence but is instead a rule of substantive law” that fosters “the certainty and stability of contracts”). Indeed, the Federal Rules of Evidence and most state rules of evidence do not even mention the parol evidence rule as an evidentiary rule. Professor E. Allen Farnsworth succinctly summarizes why the parol evidence rule should be thought of as a rule of substantive contract law:
Admittedly, the [parol evidence] rule is exclusionary making certain kinds of evidence inadmissible. But this does not make it a rule of “evidence”, for it is not based on the idea that the evidence excluded is “for one or another reason an untrustworthy or undesirable means of evidencing some facts to be proved.” Rules of Evidence, such as the hearsay rule, bar some methods of proof to show fact but permit that fact to be shown in a different way. In contrast, the parol evidence rule bars a showing of the fact itself—the fact that the terms of the agreement are other than those in the writing.
E. Allan Farnsworth, Farnsworth on Contracts, § 7.2, at 212-213 (2d ed. 1998) (subscription or purchase required).