"You have heard that it was said, 'Eye for eye, and tooth for tooth.'But I tell you, Do not resist an evil person. If someone strikes you on the right cheek, turn to him the other also. And if someone wants to sue you and take your tunic, let him have your cloak as well. If someone forces you to go one mile, go with him two miles. Give to the one who asks you, and do not turn away from the one who wants to borrow from you." [Matthew 5:38-42]
I came across an introductory note in a book I was reading that mentioned confusion by early 16th century Protestants over exactly how texts like Matthew 5:39 and Romans 12:19 should be understood. The problem was how far Protestants should go to obey secular authorities. Confusion arose because Roman Catholics typically interpreted these texts as "counsels for the perfect," and not precepts for all Christians. This intrigued me, and I searched around to find out what all this was about.
The Catholic Encyclopedia explains:
Christ in the Gospels laid down certain rules of life and conduct which must be practiced by every one of His followers as the necessary condition for attaining to everlasting life. These precepts of the Gospel practically consist of the Decalogue, or Ten Commandments, of the Old Law, interpreted in the sense of the New. Besides these precepts which must be observed by all under pain of eternal damnation, He also taught certain principles which He expressly stated were not to be considered as binding upon all, or as necessary conditions without which heaven could not be attained, but rather as counsels for those who desired to do more than the minimum and to aim at Christian perfection, so far as that can be obtained here upon earth.
I wouldn't normally quote Wikipedia, but they actually were one of the few sources I found that explained this:
The Double Standard View is the official position of the Roman Catholic Church. It divides the teachings of the Sermon [on the mount] into general precepts and specific counsels. Obedience to the general precepts is essential for salvation, but obedience to the counsels is only necessary for perfection. The great mass of the population need only concern themselves with the precepts; the counsels must be followed by only a pious few such as the clergy and monks. This theory was initiated by St. Augustine and later fully developed by St. Thomas Aquinas, though an early version of it is cited in Did. 6:2, "For if you are able to bear the entire yoke of the Lord, you will be perfect; but if you are not able to do this, do what you are able" (Roberts-Donaldson), and reflected in the Apostolic Decree of the Council of Jerusalem (Acts 15:19-21). Geoffrey Chaucer also did much to popularize this view among speakers of English with his Canterbury Tales (Wife of Bath's Prologue, v. 117-118)
And also, this source states:
In the Middle Ages twelve counsels were commonly enumerated, which were found especially in the Sermon on the Mount; and after the aforesaid three general heads, which concerned the religious orders, there were recommended, for instance, the injunctions " love your enemies " (Matt. v. 44), " resist not evil " (Matt. v. 39-41), etc.
And this source states:
"Commandments are given ' about those things which are necessary to attain the end of eternal felicity,' but the counsels ' about those things by which one may obtain this end better and sooner.' In general the counsels deal with poverty, chastity, and obedience, but there was an enumeration of twelve culled from the Sermon on the Mount, including, e.g., the injunctions 'Love your enemies' and 'Resist not evil.'"
It appears a typical Roman Catholic needs to try and at LEAST keep the outward law. But, if you'd like to go a bit further, then work a little bit on your heart.
Happy Reformation Day.