On the contrary, The Philosopher (Ethic. v, 10) states it to be a virtue.
I answer that, As stated above (I-II, Q. 96, A. 6), when we were treating of laws, since human actions, with which laws are concerned, are composed of contingent singulars and are innumerable in their diversity, it was not possible to lay down rules of law that would apply to every single case. Legislators in framing laws attend to what commonly happens: although if the law be applied to certain cases it will frustrate the equality of justice and be injurious to the common good, which the law has in view. Thus the law requires deposits to be restored, because in the majority of cases this is just. Yet it happens sometimes to be injurious—for instance, if a madman were to put his sword in deposit, and demand its delivery while in a state of madness, or if a man were to seek the return of his deposit in order to fight against his country. In these and like cases it is bad to follow the law, and it is good to set aside the letter of the law and to follow the dictates of justice and the common good. This is the object of epikeia which we call equity. Therefore it is evident that epikeia is a virtue.
Reply Obj. 1: Epikeia does not set aside that which is just in itself but that which is just as by law established. Nor is it opposed to severity, which follows the letter of the law when it ought to be followed. To follow the letter of the law when it ought not to be followed is sinful. Hence it is written in the Codex of Laws and Constitutions under Law v: "Without doubt he transgresses the law who by adhering to the letter of the law strives to defeat the intention of the lawgiver."
Reply Obj. 2: It would be passing judgment on a law to say that it was not well made; but to say that the letter of the law is not to be observed in some particular case is passing judgment not on the law, but on some particular contingency.
Reply Obj. 3: Interpretation is admissible in doubtful cases where it is not allowed to set aside the letter of the law without the interpretation of the sovereign. But when the case is manifest there is need, not of interpretation, but of execution. _______________________
SECOND ARTICLE [II-II, Q. 120, Art. 2]
Whether Epikeia Is a Part of Justice?
Objection 1: It seems that epikeia is not a part of justice. For, as stated above (Q. 58, A. 7), justice is twofold, particular and legal. Now epikeia is not a part of particular justice, since it extends to all virtues, even as legal justice does. In like manner, neither is it a part of legal justice, since its operation is beside that which is established by law. Therefore it seems that epikeia is not a part of justice.
Obj. 2: Further, a more principal virtue is not assigned as the part of a less principal virtue: for it is to the cardinal virtue, as being principal, that secondary virtues are assigned as parts. Now epikeia seems to be a more principal virtue than justice, as implied by its name: for it is derived from epi, i.e. "above," and dikaion, i.e. "just." Therefore epikeia is not a part of justice.
Obj. 3: Further, it seems that epikeia is the same as modesty. For where the Apostle says (Phil. 4:5), "Let your modesty be known to all men," the Greek has epieikeia [*to epieikes]. Now, according to Tully (De Invent. Rhet. ii), modesty is a part of temperance. Therefore epikeia is not a part of justice.