Information not found within the four corners of a document, agreement, or contract constitutes evidence from external sources. This type of information is utilized to clarify ambiguous language, demonstrate the intent of the parties involved, or resolve discrepancies in a written instrument. An example would be prior communications between parties to a contract that shed light on their understanding of a particular clause.
The use of this type of evidence is crucial for ensuring fairness and accuracy in legal proceedings where the meaning of a written agreement is contested. Admitting this information can prevent unjust outcomes that might arise from a strictly literal interpretation of the text. Historically, its admissibility has been subject to legal restrictions, balancing the need for clarity against the desire to uphold the integrity of written agreements and prevent fraudulent claims.