405. In order that the reason for a dispensation be sufficient, it is not required that it be so grave as to constitute a physical or moral impossibility of keeping the law, since the obligation of the law ceases in the face of impossibility (see 317, 487), without the need of dispensation. Hence, lesser reasons suffice for dispensation. 406. A dispensation must be granted whenever the law itself or justice requires it. The following cases are usually given: (a) when there exists a reason that requires, according to law, that a dispensation be granted; (b) when the common good, or the spiritual good of an individual, or his protection from some considerable evil, demands the concession of a dispensation. 407. A dispensation may be either granted or denied, when the case does not demand it and the superior after careful investigation is not certain whether the reason is sufficient or insufficient; otherwise, a greater responsibility would rest on the superior than the law can be thought to impose--viz., that of attaining certainty where it cannot easily be had. 408. He who dispenses without a sufficient reason is guilty of the sin of favoritism, and is responsible for the discontent and quarrels that result. He is guilty of grave sin thus: (a) if serious scandal or other inconvenience is caused, even when the dispenser is the lawgiver himself; (b) if the law obliges under grave sin and the dispensation is not granted by the lawgiver, but by an inferior who usurps the right to dispense. 409. The subject of dispensation is guilty of sin: (a) if he asks a dispensation when he knows for certain that there is no sufficient reason for it; (b) if, having been denied a dispensation, even though unjustly, he acts against the law; or if he knowingly makes use of an invalid or expired dispensation. 410. Sufficient reasons for a dispensation can be reduced to two classes: (a) private welfare (e.g., the difficulty of the law for the petitioner, a notable benefit he will receive through the dispensation, etc.); (b) public welfare (e.g., the benefits that are secured to the community, or the evils that are avoided through the dispensation). 411. _Epieikeia_.--Since human laws regulate particular and contingent cases according to what usually happens, and since they must therefore be expressed in general terms, exceptional cases will occur that fall under the law, if we consider only the general wording of its text, but that do not fall under the law, if we consider the purpose of the lawgiver, who never foresaw the exceptional cases and would have made different provision for them, had he foreseen them. In such exceptional cases legalism insists on blind obedience to the law-books, but the higher justice of _epieikeia_ or equity calls for obedience to the lawgiver himself as intending the common welfare and fair treatment of the rights of each person.