Equally important was the concept, widely accepted today, that a contract is a promise knowingly made to another person. The existence of a contract, particularly oral agreements, was proved by testimonial evidence. Because most persons could not write at that time, the seal constituted evidence of their contracts, even when use of the seal was unauthorized. Early contract law then presaged the conflict between objectively measured consent and the central idea that contracts are deliberate acts of promise. In modern contract law, the conflict between constructive consent and actual agreement is more pronounced.
Most contracts now are standard form contracts.
The adhering party does not have the option to negotiate for different terms and, as a practical matter, would not incur the opportunity costs of negotiation. Persons generally agree to be bound by standardized terms by signature or some other tangible sign of assent. Orthodox principles of contract law require enforcement of standardized terms regardless of a party's actual consent or knowledge of terms. The result of this basic contract rule is inapt when applied to standardized contract terms. Parties are neither free to negotiate most contract terms nor able to make rational judgments consenting to these terms prior to making the contract.