Article First. On the Obligation of Law in General.

161. Existence of obligation. 1. Any law whatever induces obligation in conscience or under sin: for the first and essential effect of law is the obligation of observing the law; wherefore a law which in no way obliges in conscience, not even to undergoing punishment, is not a law.

Therefore it is established also that the civil legislator establishes laws obliging in conscience. This is clear a. from the nature of the power conferred by God Himself, in which there is the office of preserving the common good and warding off an anarchic condition from civil society; b. from Scripture: There is no power except from God . . . Therefore he who resists the power resists the ordinance of God. Be subject not only because of wrath, but also because of conscience.¹

2. It depends upon the prudent will of the legislator what obligation he wishes to impose, whether to fault, or to fault and to punishment, or only to punishment.

This will of the legislator is discerned:

a. From the nature of the law: for civil laws in which the end intended by the legislator cannot be obtained short of obligation to fault are judged to oblige to fault; but those whose end can be obtained even short of obligation to fault are judged to oblige only to punishment.

b. From custom, which is the best interpreter of laws: namely if even subjects who are of timorous conscience practically hold the law as penal, it can be judged such.

c. From the declaration of the legislator himself, such as is had concerning the rules of certain religious orders.

d. From the words of the law itself: if the law prescribes only a punishment ("he who has done this, let him undergo this punishment"), it will be penal; if it commands and at the same time imposes a punishment, it will be mixed; likewise if it does not contain preceptive words, ordinarily it will be penal, but if it contains such words, ordinarily it will be preceptive. For although the lack of commanding words is not a certain sign of a penal law, nevertheless ordinarily, if a law is issued merely assertively, it is judged to be penal, and if it is issued by way of precept or prohibition, it is judged to be preceptive.

e. From the gravity of the punishment: for if to a civil law there is added a most grave temporal punishment which has no proportion with the transgression, it is established that the law is penal. Certainly the legislator is not judged to wish to oblige to both, to incurring fault and at the same time to incurring an exorbitant punishment, unless there is question of a law of very grave moment.

¹ Rom. 13, 1. 2. 5. Cf. 1 Pet. 2, 13.

162. The quality of obligation. The obligation of a law can be grave or light; but what obligation is imposed in individual laws depends both upon the matter, and upon the circumstances and end of the law, and upon the will of the legislator.

a. A legislator can impose grave matter under light obligation: for obligation depends upon the will of the legislator, who can reasonably prescribe even grave matter under light obligation, namely where the end of the law is sufficiently obtained even by a light obligation.

Wherefore, in order that a law oblige under grave sin, two things are required: grave matter and the intention of the legislator wishing to oblige under grave sin. That the matter is grave is gathered from the nature of the thing, from the end of the law, and from the circumstances. That the obligation of grave matter is grave from the intention of the legislator is discerned especially: a. from the words of the law, which, if they have great force ("we strictly, rigorously prescribe; we command in virtue of holy obedience; we command under threat of divine judgment"), signify grave obligation; b. from the gravity of the matter: for in grave matter, namely that which contributes much to obtaining the end intended by the law, the legislator is judged to have wished to oblige under grave sin, unless the contrary is established; c. from the gravity of the punishment: for if a grave spiritual punishment is added to the law, e.g. an excommunication latae sententiae, it is a sign that the law obliges under grave sin; nevertheless in civil law an extraordinarily great punishment generally signifies a penal law; d. from the interpretation of doctors; e. from custom or from the sense and practice of subjects.

Concerning the intention of the legislator, however, note these things: just as it is not necessary that the legislator explicitly intend to impose obligation in conscience in order that the law oblige in conscience, so it is not necessary that he explicitly intend to impose grave obligation in order that the law oblige under grave sin; for just as the intention of obliging is judged to be contained in the very use of legislative power, so in like manner the legislator is generally presumed to wish to enjoin grave matter also under grave obligation. Wherefore it must altogether be held that even an infidel legislator establishes laws obliging in conscience. Yet if it is established that an atheist legislator, making nothing of obligation before God and in conscience, acknowledges only an obligation to punishment to be inflicted on transgressors, it is rightly supposed that his laws are merely penal, unless they absolutely require obligation in conscience.

b. A legislator cannot enjoin light matter under grave obligation, because light matter is not capable of grave obligation: for an obligation which is not proportioned to the matter would be an intolerable burden, and therefore would fall rather to the detriment of subjects, because sins would be multiplied too much.

Hence if the matter is simply light, the transgression is not mortal, even if the legislator had wished to oblige under grave sin; and if a law obliging under grave sin is violated in light matter, the transgression likewise is only light. Yet if matter light in itself becomes grave from the end or from the circumstances, without doubt it can be imposed under grave sin: thus it is grave if a celebrant omits to pour a little water into the chalice.

163. To what a law obliges. The obligation which a law induces contains in itself several elements either explicitly or implicitly; it obliges:

1. To the observation of itself; this is the chief and essential efficacy of law, in which the other obligations are contained implicitly and virtually.

2. To knowledge of itself: for since law cannot be observed unless it is known, therefore, lest legislation become useless, it must first prescribe knowledge of itself. But by that very fact it also obliges to employing the ordinary means which conduce to knowing the law.

a. Hence voluntary or vincible ignorance of some precept obliging here and now is a sin against that very precept which is unknown, and indeed grave, if the ignorance has proceeded from grave negligence.

b. If somewhere statutes to be observed by clerics are promulgated and disseminated by the bishop in the diocesan paper, clerics are bound to buy the paper or at least sometimes to inquire from others who read it what has been established by the bishop: for this is the ordinary means of knowing the statutes of the bishop, which all are therefore bound to employ.

3. To employing the ordinary means which are proximately necessary for the observance of the law itself: for he who is bound to the end is by that very fact also bound to the means which are proximately necessary for obtaining the end. But to employing extraordinary and remote means the law does not oblige, because this obligation would be too burdensome and difficult.

He who is bound to recite the divine office is bound to procure and preserve for himself a breviary by which he can recite it; and he who foresees that on the very day of fasting he will not be able to have fasting foods is bound to procure them the day before, so that he can observe the fast.

4. To removing or forestalling impediments which render its observance proximately impossible, if this can be done without grave inconvenience: for he who is bound to the end is by that very fact also bound to removing or not placing impediments which proximately obstruct the obtaining of the end.

He who on the very day of fasting goes out hunting without just cause, foreseeing that because of fatigue he cannot fast on that day, sins against the precept of fasting; and he who on a feast day in the morning makes himself drunk, foreseeing that on that account he cannot be present at Mass, commits an offense not only against temperance but also against the precept of hearing Mass.

5. To avoiding the danger of sinning against the law: for the law which commands avoiding sin by that very fact commands also avoiding that which is morally joined with sin, namely the danger of sinning.

Therefore he who without just cause exposes himself to the danger of sinning sins against the same precept of whose violation he seeks the danger: for to will the danger of sinning is the same as to will the sin itself, which is greater the greater the danger is.