Section 1. On the Qualities of Consent

530. In order that a contract be valid by natural law, consent must be:

True, or internal, not only external or fictitious; for the transfer of right, which is made through a contract, and the obligation which follows from it, proceed from the will of the contracting party; therefore when this is lacking there can be no contract.

a. Fictitious consent is had when someone indeed contracts externally, yet interiorly lacks the mind of contracting, or, what comes to the same thing, the mind of obligating himself: for the mind of obligating oneself coheres by necessary nexus with the will of contracting. The will of fulfilling the contract is to be distinguished from the will of contracting and obligating oneself.

b. He who fictitiously consents, or who contracts without the mind of obligating himself, enters no contract; therefore by reason of the contract he is bound to nothing. But if one feigning consent and deceiving another by it has inflicted damage on him, he is bound to repair this damage, and if he cannot repair it otherwise, he is bound to fulfill what he fictitiously promised.

c. He who enters a contract with the will of contracting, but with the will of not fulfilling the contract, contracts validly and therefore takes on a true obligation and is bound by force of the contract to fulfill it.

d. Fiction in contracting is not presumed, but must be proved. Yet if fiction happens in those circumstances in which it could easily be detected by the other contracting party, in each forum the other is presumed to have sufficiently detected the fiction, and therefore he who fictitiously consents cannot be obligated to compensation: for no injury is done to one knowing and willing.

531. Free and deliberate, that is, furnished with that advertence, deliberation, and liberty which are required for a perfectly human act, whether the contract concerns grave matter or light matter: for the contracting party imposes on himself a true and perfect obligation of justice; but this can proceed only from a perfectly human act.

Therefore a contract entered with half-deliberate consent, even of only one contracting party, is null. And this is the reason why the half-witted, half-drunk, half-asleep, etc., cannot enter a valid contract, in the same way as the same persons cannot emit a valid vow, even one obliging only under light obligation.

532. Mutual, that is, furnished by each contracting party concerning the same object: for one cannot by his own will acquire a right for another and obligate him to himself unless he himself wishes and consents. Therefore a unilateral contract is not perfected unless the other accepts the offered right; but a bilateral contract is not perfected unless each accepts the offered right.

a. It is not required that the consent of each contracting party be elicited and expressed at the same time, but it suffices that the consent of one has not been revoked, but virtually or morally still endures when the other elicits and expresses his consent. Wherefore that the consent of contracting parties must be simultaneous signifies nothing else than that the consent of one must be furnished as long as the consent of the other endures.

b. He who offers a contract to another can by natural law also determine the time within which the other must consent to the contract, and therefore can determine how long his consent virtually endures. Wherefore if the other consents within this time, the contract is valid; but if he consents after this time, the contract has no force because of the defect of mutual consent. Likewise he who offered a contract to another can by natural law withdraw from his offer as long as the other has not yet given consent. But to exclude disputes which could arise from this source concerning the value of contracts, positive laws are accustomed to establish how long the consent of him who offers a contract to another is considered to endure, and how long the one offering a contract can withdraw from his offer. Therefore civil codes must be consulted concerning this matter.¹

c. If a contract is made through a procurator, the contract is essentially perfected when the procurator consents, even if the contracting party himself has not yet consented: for the consent of the procurator is morally considered to be the consent of the contracting party himself.

¹ C.A. Section 862; Commercial Code 318-322; C.G. Sections 147, 149.

533. Manifested by a sensible sign, so that it can be perceived and accepted by the other: for acts which pertain to the mutual commerce of men must be manifested by external signs. Hence if someone offers a contract to another, it is not perfected when the other internally consents, but when his consent is externally manifested.

a. By natural law, for the value of a contract, words are not required, whether spoken by mouth or written, but any external sign which is apt for expressing consent suffices; yet positive laws, to forestall disputes, sometimes command that contracts be perfected by words or writing, so that contracts entered without these signs are either invalid or at least do not produce a civil obligation.

b. Whether the silence of him to whom a contract is offered is a sufficient sign of consent. alpha. Silence is held as consent if the contract is favorable to the one silent, as in a promise or donation: for acceptance of a favor is deservedly presumed and, when even a very slight sign accedes, becomes certain. beta. Silence is held as consent also in onerous contracts if the one silent can easily contradict and, if he does not consent, must manifest dissent. gamma. But silence in onerous contracts is not held as consent if the one silent either cannot easily contradict or is not bound to express dissent.

At what moment of time contracts among the absent are perfected; in other words: whether for the value of a contract it is required that the consent of the one accepting be intimated to the one offering, or whether the contract is perfected at the time at which the one accepting externally manifests his consent by a sign, before this manifestation becomes known to the one offering.

a. In unilateral contracts it is not required that acceptance be manifested to the one offering; therefore a promise or donation has force when the other has accepted it, even if the acceptance has not yet become known to the one promising or giving: for besides acceptance of the offered right, nothing else is required by natural law for perfecting these contracts. Yet positive laws sometimes demand that acceptance must be intimated to the other party.

b. In bilateral contracts it is more probable that it is necessary that the acceptance of the other become known to the one offering: for just as the consent of the one offering does not oblige him unless it has been manifested to the other contracting party, so of itself the consent of the one accepting does not oblige him unless it is known to the one offering, because in bilateral contracts the one accepting also offers something on his part. Therefore the contract is perfected at that moment when the acceptance of the other becomes known to the one offering. Hence if a contract is made among the absent by letters, the contract is more probably perfected when the consent of the one accepting becomes known to the one offering from the letters of reply. Yet the contracting parties can establish that the contract have force when the one accepting consents, before the consent becomes known to the one offering.¹ Positive laws likewise sometimes establish that a contract is already perfected by acceptance alone.

¹ Cf. Lugo, disp. 22, n. 26 ss.; Marres l. 3, n. 53; Vermeersch n. 316 ss.