Chapter VI. The Obligation of Law

By obligation we here understand a moral necessity arising from a law to do or to forbear doing something. It is said to be a moral necessity, not physical, because it does not subject the person bound to physical but moral constraint to act according to the law; he must act thus if he would do his duty, if he would act reasonably, if he would escape guilt, sin, and punishment.

In a slightly restricted sense a moral obligation is said to be imposed on those subject to a law which binds in conscience under pain of committing sin. Such a law is called a moral law. If the intention of the legislator is not to bind the conscience under pain of sin, but only under pain of paying the penalty imposed, the law is called a penal law. If the law binds under pain of sin, and also imposes a penalty on transgressors, it is called a mixed law.

The obligation of a law depends primarily on the will of the legislator. For we are here considering not the natural law, which is imposed by the very nature of things and by God, but positive law, which depends on the will of the legislative authority for its existence, and so also for the kind and quantity of obligation which it imposes. The legislator may intend to impose a moral obligation under pain of sin, for God commands us to obey our lawful superiors when they impose a strict precept on us, and disobedience to them is an offence against him and a sin. If the matter is of sufficient importance, he may intend the obligation to be serious, so that a breach of it would be grievously sinful, or he may intend it to be only slight, whose breach would be a venial sin. It would be unreasonable to intend to bind under pain of grave sin in a light and trivial matter, and so a human legislator cannot do this. The legislator may also, if he choose, intend to bind only under pain of paying the penalty, and then the subject in case of violation of the law will only be bound in conscience to do this. The kind of obligation, then, which a law imposes depends principally on the will of the legislator, but secondarily also on the matter of the precept.

The kind and quantity of obligation imposed by any particular law may be gathered from the express mind of the lawgiver. If the matter be capable of a grave obligation, and in making the law words indicating a strict precept are used— e.g., we command, we severely ordain—the presumption is that the law imposes a grave moral obligation. The same may be said if a grave censure or other grave penalty is imposed on transgressors. The interpretation of Doctors, and the way in which custom interprets a law, are also guides to its binding force.

An affirmative law, which commands something to be done, is said to bind always but not for always. Thus we are commanded to pray always—i.e., never to abandon prayer— though we are not obliged continually to pray all day long, but only at suitable times. A negative precept, on the other hand, binds always and for always, so that we must continually act according to its prescriptions, At no time on days of obligation may we do servile work.

A law imposes in the first place an obligation on those subject to it to inform themselves of its existence and provisions, for it imposes the duty of observing it, and this cannot be done unless the terms are known; knowledge of the law is the necessary means to the end. A law also forbids us to put ourselves in the proximate occasion of transgressing it, for the avoidance of such proximate occasions is also a necessary means for the observance of the law.

A negative law is observed by abstaining from what is forbidden, for that is the intention of the lawgiver. Provided that we abstain from servile work on a Sunday, we fulfil that part of the law; no special intention of not working or of fulfilling our obligation is required. An affirmative law which prescribes something to be done sometimes requires a conscious human act for its fulfilment; sometimes it does not. If the obligation be merely real, as the duty of paying a debt, even unconscious payment will suffice, provided that the creditor gets what belongs to him. If a personal obligation is imposed of performing some action—e.g., hearing Mass—the action must be performed in a human manner, by a conscious, voluntary act. It is not, however, necessary to intend to fulfil the purpose of the law; we satisfy the precept of hearing Mass by intending to hear it and actually doing so; to fulfil the obligation it is not necessary to intend to honour God, nor even to be in a state of grace; the end of the precept does not fall under the precept, as the adage has it.

We may sometimes satisfy two obligations by one and the same action, as when a day of abstinence, on account of a vigil, falls on a Friday, or a day of obligation falls on a Sunday. Sometimes, however, the nature of the obligation or the presumed will of the legislator prohibits this being done. If a confessor imposed the hearing of Mass for sacramental penance, it would ordinarily be intended that a Mass not otherwise of precept should be heard. Nothing hinders the simultaneous fulfilment of two different obligations by actions which do not clash. A priest may well say his breviary while hearing a Mass of obligation.

If the whole of an obligation cannot be fulfilled, we are not thereby excused from fulfilling a part, if the matter is capable of being divided, and thus in some degree the end of the law is secured. If a priest, for example, cannot say the whole breviary, he must say what he can, if the portion which he can say be considerable and the form prescribed by the Church be observed. However, if a Bishop could not go the whole way to Rome to make his visit ad limina, there would be no obligation of going as far as he could. 9. When a fixed time is appointed for the fulfilment of an obligation, sometimes, according to the will of the legislator, after the term has passed, the law no longer binds; sometimes, on the other hand, the obligation must still be fulfilled. Thus, if a priest lawfully or unlawfully has omitted his breviary, he is not bound to make it up on the following day, or if one of the faithful miss Mass on a Sunday, he is not bound to supply the omission by hearing it on a week day. On the other hand, if a debt has not been paid on the date agreed on, it must be paid as soon as possible afterward, and if the Easter Communion has not been made at the proper time there still remains the duty of making it.