Consensus ad idem

Consensus ad idem means agreement on the same thing, often described as a meeting of minds. It is the foundation of consent in contract. Section 13 of the Indian Contract Act, 1872 gives it statutory form: two or more persons are said to consent when they agree upon the same thing in the same sense. Consent is therefore objective identity of understanding on the subject matter and terms, not merely an outward appearance of agreement.

The doctrine must be kept apart from free consent. Section 13 asks whether there is consent at all, while Section 14 asks whether consent that exists is free, that is, not caused by coercion, undue influence, fraud, misrepresentation or mistake. Where consent exists but is not free, the contract is generally voidable under Section 19 or 19A. Where there is no consensus ad idem, because the parties are thinking of different things, there is no real agreement and the transaction is void.

Two situations commonly show the absence of consensus. The first is a mutual mistake of fact essential to the agreement, which makes the agreement void under Section 20; the English case Raffles v. Wichelhaus (1864), where the parties meant two different ships of the same name, is the usual illustration. The second is error in the nature of the document signed, where a person is induced to sign something fundamentally different from what he thought he was signing, which courts treat as no consent at all. In Tarsem Singh v. Sukhminder Singh (1998) the Supreme Court held an agreement to sell land void under Section 20 where the parties were mistaken about whether the area was in kanals or bighas, since the area was essential to the agreement.

Examiners test the wording of Section 13, the distinction between absence of consent (void) and absence of free consent (voidable), and the mutual mistake cases.