What principle does the "parol evidence rule" uphold?

The principle upheld by the parol evidence rule is that it prohibits introducing oral agreements or prior written agreements that contradict the clear and unambiguous terms of a written contract. This rule operates under the premise that once parties have put their agreement into a final written form, any external evidence that seeks to alter or contradict that written content is not admissible in court. The intention is to protect the integrity of written contracts and ensure that their terms are enforced as agreed upon by the parties.

In a legal dispute, if the written contract is deemed to be the complete and final agreement, any oral statements made prior to or at the time of the contract signing that attempt to change those terms are rendered ineffective. This protects the parties from relying on earlier discussions or understandings that may conflict with what is documented in the final agreement. Thus, the parol evidence rule enforces the idea that the written contract is the definitive source of the parties’ intentions and obligations.