The Four Corners Rule: A Key Principle in Contract Interpretation

The four corners rule comes from English-American common law of contract and document interpretation. The metaphor refers to the four edges of a written page: when a contract is clear, its meaning must be derived solely from the document's text, not from outside circumstances or what the parties said.

There is no single, clearly identifiable year of origin. The rule is not a statute but developed gradually out of the traditional common-law doctrine that written contracts with clear wording should be interpreted literally, and that extrinsic evidence is only allowed when the language is ambiguous. The modern name and its widespread use are primarily American, but the underlying text-first principle is much older and has English roots.