CHAPTER VI
ON THE OBLIGATION OF LAW
I. 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.
2. 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 an4 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.
