Definition
Epikeia. n. The principle in ethics that a law can be broken to achieve a greater good.
Reasonable
Ancient Greek
Presented by Aristotle
Explained and retained by St. Thomas Aquinas in Summa Theologica
“It was not possible to lay down rules of law that would apply to every single case. Legislators 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.”
St. Thomas teaches in the Summa that epikeia o equity is part of the virtue of justice. He describes the use of epikeia as follows: “It was not possible to lay down rules of law that would apply to every single case. Legislators… 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.” (St. Thomas then goes on to give the examples of application in the use of epikeia, such as a madman who has deposited his sword with another and wishes to redeem it to do harm, or fight against his country. In another place, St. Thomas cites the example of citizens fleeing from an enemy. The gates of the city are ordered locked by the authorities, but the use of epikeia demands that they be opened for the welfare of these citizens.)
“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.” However, “Epikeia does not set aside that which is just in itself, but that which is just by law established.” (“Summa Theologica,” Pt. II-II, Q. 120 , Art. 1
Source: http://betrayedcatholics.com/wpcms/articles/a-catholics-course-of-study/canon-law/the-origin-and-use-of-epikeia-links/
Originally for the interpretation of legal conceptions of the