The common law of contract treats the proposal of additional terms as a rejection and a counter offer. The UCC treats a merchant's proposal of additional terms to a merchant as creating a contract with the additional terms added to the original offer. The USA Constitution Article I, Section 8, clause 8, the patent and copyright clause, grants the Congress powers as well as limits Congress' use of the granted powers. The UCC provides detailed written terms to flesh out oral contracts and the UCC allows the parties to alter any term within the UCC except for a merchant's liability for a consumer's personal injury arising from use of a consumer product. The law attempts to satisfy your reasonable expectations by favoring that which can be proved objectively over that which is subjective.
All torts have the same basic elements.
The defendant must breach a duty of care owed to the plaintiff. The defendant's breach must be the causation in fact and the proximate cause of the plaintiff's injury. Also, the defendant must not have any defenses. In a contract the parties, time, consideration, and subject matter each is a material term for analyzing an allegation of unilateral mistake. These four factors are listed in declining order of importance.