(b) it is dangerous, for it rests on the judgment of the individual, which is prone to decide in his own favor to the detriment of the common good as well as of self.
414. _Epieikeia_ by its very nature imposes certain limits on its use.
(a) It is based on the fact that a certain case is not comprehended in a law, because the legislator did not foresee it.
Hence, _epieikeia_ is not applicable to the Divine Law; for the Divine Lawgiver foresaw all cases that could arise, and so excluded all exceptions (see 315). This is clear as regards the Ten Commandments and other precepts of the Natural Law, since they deal with what is intrinsically good or bad, and are unchangeable (see 307). But it applies also to the prescriptions of the Positive Law of God, and apparent cases of _epieikeia_, such as the eating of the loaves of proposition by David (I Kings, xxi. 6), can be explained by the cessation of law or divine dispensation. Examples: One may not excuse certain modern forms of cheating on the plea that they were not thought of when the Decalogue was given. One may not omit Baptism on the ground that Christ Himself would have excused from it, had He foreseen the circumstances.
(b) _Epieikeia_ is based on the principle that the words of a law must be subordinated to the common good and justice. Hence, it is not applicable to those laws whose universal observance is demanded by the common good—that is, to irritant laws. Any hardship suffered by an individual through the effect of such laws is small in comparison with the injury that would be done to the common welfare if there were any cases not comprehended in such laws; for irritant laws are the norms for judging the validity of contracts and other acts, and public; security demands that they be uniform and certain. Example: One may not contract marriage with a diriment impediment, on the plea that the Church would not wish the impediments to oblige under the serious inconvenience that exists in one’s case.
415. The dangers of _epieikeia_ also place limitations on its use.
(a) There is the danger that one may be wrong in judging that the lawgiver did not wish to include a case under his law. If this is not certain, one should investigate to the best of one’s ability, and have recourse, if possible, to the legislator or his representative for a declaration or dispensation. It is never lawful to use _epieikeia_ without reasonable certainty that the legislator would not wish the law to apply here and now.
(b) There is the danger that one may be in bad faith in deciding that the common good or justice requires the use of _epieikeia_; the motive in reality may be self-interest or escape from obligation, Hence, a person should not use _epieikeia_ except in necessity, when he is thrown on his own resources and must decide for himself; and, even then, he must be sure that he acts from sincerity and disinterestedness.
416. Cases in which the use of _epieikeia_ is lawful are the following:
(a) Epieikeia in a wide sense—that is, a benign interpretation made by a private individual that a particular case is not comprehended in the intention of the lawgiver, because the latter had not the power to include it—may be used for all cases in which the opposite interpretation would set the law up in opposition to the common welfare or would work injustice to individuals. Example: The law that goods borrowed must be returned to their owners yields to _epieikeia_, if there is question of putting weapons into the hands of one who would use them against the public security or for the commission of murder;