“The basic principle is often called the ‘parol evidence rule’, and according to this rule evidence is not admissible to contradict or qualify a complete written contract. The rule is usually stated in the form of a rule of evidence, but it is probably best regarded as a rule of substantive law. The question is not really whether evidence can be admitted which might vary the written document, but whether, if the evidence is admitted, it will have the legal effect of varying the document.” P.S. Atiyah, An Introduction to the Law of Contract 161–62 (3d ed. 1981).
“The parol evidence rule assumes that the formal writing reflects the parties’ minds at a point of maximum resolution and, hence, that duties and restrictions that do not appear in the written document, even though apparently accepted at an earlier stage, were not intended by the parties to survive. In addition, and quite apart from the survival of matters discarded in the course of negotiations, there is the obvious danger of outright fraud.” Marvin A. Chirelstein, Concepts and Case Analysis in the Law of Contracts 82–83 (1990).
