383. The intention of the legislator to impose a grave moral obligation is recognized either: (a) from his own declaration, as when a church law is commanded under threat of the divine judgment; or (b) from circumstances that indicate such an intention, such as the gravity of the subject-matter of the law or the kind of penalty it prescribes, the general opinion of authorities, or the common practice of the community. 384. By obliging to the observance of what they command and the avoidance of what they forbid, laws indirectly oblige to what is necessary for such obedience. (a) Hence, the law obliges one to make use of the ordinary means for its fulfillment. Examples: He who has not used ordinary diligence to know the law, sins against the law if he violates its prescriptions. He who eats meat on a day of abstinence, because he neglected to provide himself with other food, is guilty of sin. (b) The law obliges one to use sufficient diligence in removing impediments to its fulfillment or dangers of its violation. Examples: The law of hearing Mass on Sunday obliges one not to stay up so late on Saturday that fulfillment will be impossible. The law of fasting obliges one to avoid dangerous occasions of its violation. 385. Interpretation.--Though laws are carefully framed as to language, doubts about their meaning will often arise--in ordinary cases, because of lack of understanding or changes of conditions, and in extraordinary cases, because from the circumstances the law seems inapplicable. Hence the need of explaining the law, which is done in ordinary cases by interpretation, in extraordinary cases by _epieikeia_ (see 411 sqq.). 386. Interpretation is a genuine explanation of the law, that is, one that states the meaning of the words of the law according to the intention the lawgiver had in mind when he chose them. It is of various kinds. (a) According to the author from whom it proceeds, interpretation is authentic, if it comes from the lawgiver himself or from another authorized by him; it is usual, if it comes from common usage (i.e., from the manner in which the law is customarily observed); it is doctrinal, if it is made by learned men according to the rules of correct exegesis. (b) According to the effect, interpretation is declarative, if it clears up what was obscure in the law; it is supplementary, if it extends or limits the law, by adding to or subtracting from the cases included under it. (c) According to the manner in which it is made, interpretation is strict or wide, Strict interpretation gives to a word of law that least inclusive and most proper signification it bears (e.g., it understands “son” to stand for son by birth). Wide interpretation gives to a word a more inclusive and less proper signification (e.g., it understands “son” to stand for son by birth or by adoption).