Legal Definitions - four-corners rule

The four-corners rule is a fundamental legal principle stating that when a legal document, such as a contract or a will, is clear and complete on its face, its meaning and the intent of the parties involved must be determined solely from the words written within the document itself. This means that courts will generally not consider external evidence, such as prior discussions, emails, or other agreements, if the document itself provides a full and unambiguous understanding. Furthermore, the rule requires that the document be read as a whole, rather than interpreting isolated clauses or phrases out of context.

Here are some examples illustrating the application of the four-corners rule:

• Commercial Lease Agreement: Imagine a small business signs a lease for office space. The written lease agreement clearly states that the tenant is responsible for all utility costs, including electricity and water. After moving in, the tenant claims the landlord verbally promised to cover the electricity bill for the first six months during a casual conversation before the lease was signed.

  How the four-corners rule applies: A court applying the four-corners rule would look exclusively at the written lease agreement. Since the lease unambiguously assigns responsibility for all utility costs to the tenant, the court would disregard the alleged verbal promise. The written lease is considered the complete and final agreement, and its meaning must be derived solely from its content, not from outside discussions.

• Last Will and Testament: A person's last will and testament clearly states that "all remaining assets" are to be divided equally between their two adult children. After the person passes away, a close family friend claims the deceased had always intended to leave a specific valuable antique painting to them, based on several conversations they had over the years.

  How the four-corners rule applies: Under the four-corners rule, the court would interpret the will based solely on its written terms. The phrase "all remaining assets" is clear and comprehensive. The court would not consider the external testimony about the deceased's alleged intent for the painting, as this intent was not expressed within the will itself. The will is treated as the complete expression of the deceased's wishes.

• Software Development Contract: A startup company hires a software developer to build a new mobile application. The signed contract explicitly details the scope of work, deliverables, payment schedule, and states that all intellectual property rights for the developed software will belong solely to the startup. Later, the developer claims an email exchange prior to signing the contract implied they would retain partial ownership of certain code modules they developed.

  How the four-corners rule applies: A court would apply the four-corners rule to the signed software development contract. If the contract clearly assigns all intellectual property rights to the startup, the court would disregard the prior email exchange. The contract is considered the complete and final agreement between the parties, and its meaning regarding intellectual property ownership must be derived exclusively from its written content, not from earlier communications.