Parol Evidence Rule — Part I

Extrinsic evidence opens the door wide. The parol evidence rule is the doctrine that keeps the door from swinging off its hinges. It governs whether a party may prove a prior or contemporaneous agreement that adds to or contradicts a written contract. Despite the name, it is not really a rule about oral testimony — it is a rule about finality. The deceptive thing about it is that it looks like a blanket exclusion and is actually conditional: the first question is never “is this evidence barred?” but “did the parties adopt this writing as final, and how complete is it?”

Integration and what it forecloses

R2d § 209. An integrated agreement is a writing the parties adopted as the final expression of one or more terms. If the writing is not final, the rule does not apply at all. If it is final, the next question is how complete it is.

R2d § 210. A completely integrated agreement is the final and exclusive statement of all its terms; a partially integrated agreement is final as to what it contains but not exhaustive. This distinction controls everything downstream.

R2d § 213 (the rule itself). A binding integrated agreement discharges prior agreements to the extent they are inconsistent with it; a completely integrated agreement also discharges prior agreements within its scope even if consistent. So: a partial integration bars contradictory prior terms but lets in consistent additional ones; a complete integration bars both. R2d § 216 confirms the corollary — a consistent additional term may be proved unless the writing is completely integrated, and a term that would certainly have been included in the writing is foreclosed. A merger clause (“this is the complete and exclusive agreement”) is strong, often conclusive, evidence of complete integration. Under the UCC, § 2-202 is somewhat more permissive, expressly admitting consistent additional terms unless the writing was intended as complete and exclusive. The rule has exceptions that go to validity rather than terms — fraud, duress, mistake, illegality, and conditions precedent to enforceability — because that evidence attacks the contract rather than varying it.

Cases

Gianni v. R. Russell & Co. is the anchor. A tenant signed a lease specifying what he could sell and barring tobacco; he then tried to prove an oral promise giving him the exclusive right to sell soft drinks in the building. The Pennsylvania court excluded it: because the writing already covered what he could and could not sell, an exclusive-soda right was the kind of term that would naturally have been included — so the writing was treated as the complete agreement even without a merger clause. It matters because it shows the “would-naturally-be-included” test deciding completeness from the writing’s own coverage. UAW-GM Human Resource Center v. KSL Recreation Corp. is the companion. A hotel-services contract had a merger clause; the union tried to prove a collateral oral promise that the staff would be union. The Michigan court held the merger clause conclusive — and refused to let parol evidence even reach the threshold question of integration, the objectivist Williston position. It matters because it shows a merger clause functioning as the on/off switch and a court treating integration as a question answered from the four corners.

What you should be able to do

Run the integration analysis under R2d § 209 and § 210: decide whether a writing is final, then whether it is completely or partially integrated. Apply R2d § 213 and § 216 to sort which prior or contemporaneous terms are barred (contradictory always; consistent-additional only against a complete integration) and which come in. Assess a merger clause and decide whether it conclusively establishes complete integration on the facts, and recognize the validity exceptions that survive it. Next class takes up the Williston–Corbin split head-on in Sierra Diesel.