Under the parol evidence rule, extrinsic evidence is generally not admissible to

• A. Prove the contract exists
• B. Add to or vary the terms of a complete and unambiguous writing
• C. Explain the writing’s intrinsic meaning
• D. Show that the contract was formed

Answer: (B)

The main idea is that when there is a complete and unambiguous written contract, you can’t use outside evidence to change or add terms to that writing. That’s exactly what the parol evidence rule intends: the written contract is treated as the final expression, so extrinsic material can’t be used to vary its terms.

That’s why adding to or varying the terms is the best description of what the rule generally forbids. Extrinsic evidence can still be used for other purposes, like proving that a contract exists or was formed, or helping interpret ambiguous language within the writing, but it cannot be used to alter a fully integrated contract.