Article Sixth. On the Obligation of Contracts

539. What obligation they produce. A threefold obligation arising from contract is distinguished: natural, which arises from the very nature of the contract and affects conscience, but does not produce an action in judgment; civil, which arises from civil law and produces an action in judgment, but does not oblige conscience; mixed, which obliges in conscience and at the same time produces an action in the external forum.

1. Every valid contract produces an obligation in the forum of conscience, and indeed from commutative justice (except a gratuitous promise): for the will of obligating oneself, and this from justice, is of the essence of any contract except promise. By this obligation must be fulfilled not only those things which are expressly established in the contract, but also those things which are implicitly contained in the contract either from the nature of the contract, from positive law, or from custom of the region, for example, security of eviction (n. 523, 2).

2. The gravity of the obligation arising from contract is necessarily proportioned to the matter; therefore grave in grave matter, light in light matter: for from a contract the other contracting party acquires a right; but the nature of things requires that the obligation of preserving the right of another in grave matter be grave.

Wherefore the gravity of the obligation is so independent from the intention of the contracting parties that they would make no contract if in grave matter they did not wish to contract a grave obligation. But the object of the contract and of the obligation arising from it, unless determined by nature as in marriage, depends on the intention of the contracting parties. But if the intention of the contracting parties is not clearly expressed, it must be interpreted from the common sense of the words which they used, from the nature itself of the contract, from positive law, from the usage of regions, etc.; and if from all these it is not certainly established, one must stand for the minimum.

3. A rescindable contract obliges one party until the other party, who has the right of rescinding, requests rescission; but if that party renounces the right of rescinding, it produces the same obligation as a firm contract. A contract can be rescinded by private authority, with two cases excepted, namely if the matter is doubtful or if the law prescribes that rescission must be made by a judge. A contract which is not rescinded within the time defined by law becomes firm.

Note. Sometimes contracting parties mutually agree concerning a determined sum of money (poena conventionalis - Reuegeld) to be paid by him who withdraws from the contract without a just cause. A penalty of this kind must be paid both by natural law and by civil law (C.A. Section 909), provided it was seriously added and is not immoderate.

540. On an oath added to a contract.¹ An oath added to a contract is a promissory oath by which the contracting party, under invocation of the divine name, obligates himself to fulfilling the contract. Concerning the force and efficacy of this oath added to a contract, these things must be held.

1. An oath follows the nature and conditions of the contract to which it is added, from the rule of law: the accessory follows the principal (n. 251).

Therefore betrothals can be dissolved by mutual consent, even if the betrothed persons added an oath. A promise, even if confirmed by oath, does not oblige unless it is accepted.

2. An oath added to a contract which cannot be observed without sin is invalid: for it cannot oblige to a thing even only lightly evil.

Therefore an oath is invalid when added to a promise whose object is base or illicit, even if only by positive law, for example, to a promise of helping another in defrauding taxes to be paid from precept.

3. An oath added to a contract invalid by natural law cannot render the contract valid; indeed the oath itself is invalid, even if it could be observed without sin.

a. For an oath cannot supply the defect because of which a contract of this kind is invalid. Therefore, for example, sworn betrothals which are invalid by natural law are not confirmed by the added oath.

b. The common opinion indeed teaches that in this case the oath is valid and must be observed, because every oath must be observed if this can be done without sin. Therefore he who had sworn about paying usury is obligated from religion to pay it unless he had received dispensation from the oath, although he can seek it again as unjust. But the opinion seems altogether probable which says that the oath in this case is invalid and altogether frees from paying unjust usury.²

4. An oath added to a contract invalid or rescindable by positive law alone indeed does not make the contract valid or firm, yet brings it about that it must be observed, if it can be licitly observed, by reason of the oath, unless this oath is relaxed, provided the oath added to the contract was valid: for any valid oath, out of reverence for the divine name, must be observed if it can be observed without sin. Therefore from religion a contract of this kind must be observed, even if from justice it need not be observed.

a. Concerning contracts invalid or infirm by positive law, the older authors taught that they are confirmed by an oath, because Roman law established that because of the added oath the invalidation of the law ceased and that these contracts were to be held as valid and firm in reverence of the divine name. Yet since today civil law establishes nothing of this kind, it can be affirmed that all contracts, by an oath added, are not changed in the nature of contract.³

b. Thus a minor who promised by oath that he would not rescind the contract must observe it insofar as it is just (at least after attaining majority), unless dispensation from the obligation of the oath has been obtained. If someone under oath promised a robber a certain sum of money, the promise, if it was internal, is valid but rescindable; yet the oath, as one extorted by fear, is invalid and therefore does not stand in the way of rescission of the promise.

5. An act contrary to an antecedent oath is indeed valid, yet the one acting against the oath is perjured: for an oath does not take away the power of doing what he had promised that he would not do.

Therefore the revocation of a testament has force for one who had previously sworn that he would not revoke it; the donation made to another has force for one who had previously sworn that he would give to Caius and not to another.

¹ Cf. Laymann, l. 4, tract. 3, c. 8; Lessius, l. 2, c. 17, n. 50 ss.; Marres, De iustitia^2 (Ruraemond: Romen, 1889), l. 2, n. 267 ss.

² Ballerini-Palmieri II, n. 588; Genicot I, n. 599.

³ Since the Church in this part retains the dispositions of Roman law, in sacred causes an oath added to a contract of this kind renders the contract itself valid or firm, so that it must be observed both from justice and from religion.

541. Obligation of a qualified contract. A qualified contract is one to which a clause (mode or condition) has been added which accidentally modifies its obligation. Contracts of this kind are chiefly: a. contracts entered under a condition; b. under an end; c. under a cause; d. under a demonstration; e. to a day. The added clause must be determined from its own nature.

I. Contract under a condition. 1. Notions. a. A condition is an external circumstance added to a contract, on whose existence the value of the contract depends.

b. The added condition can concern the present, the past, or the future.

A twofold condition concerning the future is distinguished: one suspensive, which brings it about that the existence of the obligation depends on the fulfilled condition, for example, I give you one hundred if you go to Rome; another resolutive, which brings it about that an already existing obligation is afterward revoked or resolved when the condition is fulfilled or not fulfilled, for example, I sell you a book unless within a week it displeases you.

c. A condition concerning the future concerns either a necessary thing, which is known will certainly be, or an impossible thing, or a possible thing, which can exist and not exist, and whose event therefore is uncertain.

2. Principles. a. A condition concerning the present or the past brings it about that the contract has force if the condition exists, and does not have force if the condition does not exist, even if its existence or non-existence is not yet established.

b. A condition concerning a necessary future does not prevent the contract from having force at once, because a condition certainly future is considered added in vain, unless the contracting party expressly wished the event to be awaited, as if someone says: I will give you a watch if tomorrow the sun rises.

c. A condition concerning an impossible future brings it about that the contract is invalid: for he who wills something under an impossible condition in fact does not will, as if someone says: I give you a gold coin if tomorrow the sun does not rise.

Here also belongs a condition concerning a base thing, which is considered as concerning a morally impossible thing. But from positive law, especially canon law, conditions concerning an impossible or base thing in all contracts of last will are held as not added. Here it must be noted that a base thing is considered not only the demand that an illicit thing be done (if you become a Lutheran), but also the demand that a good action not be done, whether it is of precept or counsel (if you do not become a religious). Therefore a testament has force even if the dishonorable condition is not fulfilled by the heirs: for anyone is considered to wish to contract according to the laws.

But if civil codes do not agree with canon law, it must be noted that testaments and pious legacies are ruled by the dispositions of ecclesiastical law, not civil law. Wherefore impossible or base conditions (at least in the forum of conscience) are held as not added, even if the civil code has established otherwise.

d. A suspensive condition concerning a possible future suspends the consent and produces the obligation of awaiting and not impeding the event of the condition; but once the condition has been fulfilled, the obligation itself of the contract arises without any other consent; for example, I will give you half if my uncle leaves me a legacy. For if the condition is not fulfilled, the contract is null; but once the condition has been fulfilled, the contract becomes absolute without another consent.¹

Note. A contract entered under this suspensive condition is usually understood if there is speech of a conditioned contract.

¹ Cf. Ballerini-Palmieri VI, n. 265 ss.

542. II. Contract under an end or under a mode is said to be one in which one contracting party prescribes to the other to what end and use he must apply the thing accepted, and the other contracting party accepts this, for example, I give Titia one thousand so that she may enter a monastery. This contract does not suspend the obligation, but has force at once, with the end not yet fulfilled, because each contracting party consents to the contract and to the mode added. But it enjoins on the other contracting party the burden of fulfilling the end or mode added.

In this a contract under a condition differs from a contract under a mode: that the condition suspends the effect until the condition is fulfilled, but the mode or end does not suspend the effect, but adds the obligation of fulfilling the end. Hence if one is given one hundred so that he may celebrate one hundred Masses, the contract is perfected at once when the other accepts the thing, and once the money has been handed over the one accepting at once acquires ownership of it; but he is bound from justice to fulfill the mode added. But if afterward the mode or end is not fulfilled, especially in donations under a mode, attention must be paid to the intention of the giver. If from the words or circumstances of the donation it is established that he intended to obligate the donee to that end, the donation, when the end has not been furnished, is resolved and the gift must be restored. If he only intended to furnish the means for furnishing the end if it should please the donee, the gift can be retained, even if the end is not fulfilled.¹

¹ Cf. Lugo, disp. 23, n. 111; Lessius, l. 2, c. 18, n. 124 ss.

543. III. Contract under a cause is said to be one by which the motive of contracting is indicated, for example, I give you one hundred because you are my blood-relative. This contract is invalid if the added cause is lacking and is the principal and primary motive; it is not invalid if the cause is a secondary and merely impulsive motive.

544. IV. Contracts under a demonstration are called those in which the matter of the contract is not accurately determined, but is rather pointed out. Now if error occurs in designating the quantity of the matter, the contract must be interpreted differently according to the diversity of designation. For if the quantity is designated demonstratively, for example, I buy this cask containing five, nothing must be supplied; but if the quantity is designated taxatively, for example, I buy five which are contained in this cask, the defect must be supplied.

545. V. A contract entered to a day is said to be one in which the day of execution is designated. If the designated day is certainly going to come, the contract obliges at once, but execution does not oblige before the designated day, for example, I give one hundred to the parish church when my father dies. But if the designated day is not certainly future, the obligation is suspended as if the contract were conditioned, for example, I give you one hundred when my son enters religion.

a. Because in the first example the contract obliges at once, and therefore the right is transferred at once, if the giver died before the designated day, the obligation of executing the donation would pass to the heirs; but in the second example, if the giver died before the entrance of his son into religion, no obligation of giving would exist in the heirs.

b. By the particle if a condition is indeed usually expressed, but sometimes not a condition but the designation of time is set forth by it, as if someone says: I give you a gold coin if (that is, when) Titius pays me the rent.

Question Second. On Unilateral Contracts

Special contracts, of which a great number exists, can be recalled to three classes: a. to unilateral contracts; b. bilateral contracts of certain event; c. aleatory contracts. To unilateral contracts pertain donation, promise, and testament. Testaments are indeed not properly contracts; nevertheless they are usually counted among contracts and explained, because they closely approach gratuitous donation.