a. Article 8 of the CISG is entitled “Interpretation of Statement or Other Conduct of a Party.” Surprisingly, the CISG makes no explicit statement concerning the interpretation of a contract that is the joint product of the parties' negotiations resulting in the adoption of common language. As Professor Honnold has noted, the provisions of Article 8 have “special significance for agreements that have not resulted from detailed negotiations.” Uncomplicated sales of goods, in which no formalized contractual documents are produced, are quite common, but more complex transactions that interweave sales with support services are also very important. The UNIDROIT Principles' focus is broader than simple sales and provides explicit guidance for the interpretation of contracts and not merely for the interpretation of individual communications. It thus fills a wide gap in the CISG text.

b. Article 4.1 of the Principles talks in terms of the interpretation of “contracts”. It starts with a subjective notion. If the parties have a common intention, the common intention will prevail. This, on the face of it, is the same rule that has been adopted by the American Restatement, but the common law objectifies intention by erecting barriers to evidence of what the parties really intended as opposed to what they said or wrote. The Principles, however, disclaim any limitation on evidence of the parties' intentions.

c. If the common intention of the parties cannot be determined, the Principles would apply an objective test to determine the meaning of the contract.