A civil-law concept defining a rule, doctrine, or procedural mechanism used to resolve private disputes. It applies when its legally specified conditions are satisfied and produces defined consequences in adjudication or settlement. It does not apply where required elements or prerequisites are not met. It materially affects rights, obligations, or available remedies in civil controversies. The concept is generally stable, though statutory and doctrinal refinements may occur over time.

Principle

Contractual obligations can be established by reciprocal promises alone, without immediate performance, when the parties manifest mutual assent to be bound by those promises.

Demonstration

A seller promises to deliver goods and a buyer promises to pay upon delivery; both parties have enforceable duties once the mutual promises are exchanged even if performance is scheduled for a later date.

Misapplication

Treating every reciprocal negotiation as a bilateral contract and enforcing obligations before clear mutual assent and terms have been exchanged, leading to premature claims.

Consequence

When properly formed, each party may sue for breach if the other fails to perform; remedies may include specific performance, damages, or cancellation depending on contract terms and governing law.

Reversal

A unilateral contract, where only one party's promise is binding contingent on the other party's performance rather than reciprocal promises giving rise to obligations.

Boundary

Excludes unilateral offers conditioned on performance, contracts void for lack of required formalities (e.g., statutes requiring written form), and agreements that are mere preliminary negotiations or letters of intent lacking binding language.

Semantic Tension

Tension arises with conditional or contingent promises—whether the exchange is truly mutual (bilateral) or an offer awaiting acceptance by performance (unilateral) depends on intent and structure of the promises.

Synthesis

A bilateral contract is an agreement of reciprocal promises creating immediate reciprocal obligations, enforceable once parties validly exchange mutual assent to those promises.