Module 2: Terms & Interpretation

When a written agreement is integrated — meant as the final, complete expression of the deal — the parol evidence rule generally bars evidence of prior or contemporaneous statements offered to contradict or add to its terms. A merger (or integration) clause, stating the writing is the complete agreement, is strong evidence of integration.

This rule is narrower than it sounds, though: it doesn’t bar evidence offered to resolve a genuine ambiguity in a term, or to prove fraud, mistake, or that a condition to the contract’s very existence was never satisfied. Those are recognized exceptions, not loopholes.

Example. Peter and John sign a written contract for John to landscape Peter’s yard for $2,000, with a merger clause stating the writing is their “entire agreement.” Peter later claims John also verbally promised, before they signed, to trim the trees for free. Because the writing is integrated, Peter generally can’t use that prior verbal promise to add a free tree-trimming term — the merger clause signals the parties meant the signed document to be the whole deal. But if Peter instead wanted to show that “the yard” in the contract was genuinely ambiguous between the front yard and the full property, that evidence would still come in, because resolving a real ambiguity isn’t the same as contradicting or adding a term.

When a term is genuinely ambiguous, courts don’t just guess. Under contra proferentem, ambiguity is generally construed against whichever party drafted the term. The UCC also recognizes a hierarchy of evidence for resolving ambiguity: express terms first, then course of performance (how the parties have acted under this very contract), then course of dealing (their pattern in prior contracts with each other), then usage of trade(industry-wide custom).

Example. Peter’s contract with John, a supplier, calls for delivery of goods in “cartons.” Peter drafted the contract and assumed a carton meant 12 units; John assumed 24, matching how every other supplier in their industry packs cartons. Because Peter drafted the ambiguous term, contra proferentem would tend to favor John’s reading against Peter. And separately, since Peter and John have no prior history together to draw a course of dealing from, the industry-wide practice — usage of trade — supports reading “carton” as 24 units.

Parties rarely address every possible issue, so courts and the UCC supply default answers for genuine gaps — this is gap-filling. Common examples include the UCC’s implied warranty of merchantability, a reasonable price or time when none is stated, and the implied covenant of good faith and fair dealing, read into every contract to prevent either side from acting to deprive the other of the benefit of the bargain.

Example. Peter agrees to buy 100 chairs from John but the contract never states a delivery date. Rather than the deal failing for indefiniteness, a court will fill that gap with a reasonable time based on the circumstances. Separately, if John starts quietly shipping Peter chairs with broken legs — technically still “chairs” — the implied covenant of good faith and fair dealing stops John from hiding behind that technicality to deprive Peter of the usable chairs he actually bargained for.

Not every contractual obligation works the same way. A promise that’s broken gives the other side a claim for damages, but generally doesn’t excuse their own performance. A condition — an event that must occur before a duty to perform arises — is different: conditions generally must be strictly satisfied, and failing to meet one can excuse the other party’s performance entirely, not just create a damages claim. The same sentence can sometimes be read either way, which is exactly why the distinction is so heavily tested.

Example. John’s contract with Peter says, “John promises to paint Peter’s house, and Peter promises to pay John $3,000.” If John simply paints late, that’s a broken promise — Peter may have a damages claim, but he generally still owes something. Now compare: “Peter shall pay John $3,000, provided that John completes the painting by June 1st.” Here, John finishing by June 1st is a condition on Peter’s duty to pay. If John finishes on June 3rd instead, Peter’s duty to pay may never arise at all — not just be reduced by damages — because the condition was never strictly satisfied.