(I found this in a Roman Catholic publication, once upon a time. I don't remember the source, nor did a quick search of the cortex reveal it. If you know whose this is, please contact me at manager208 AT gmail DOT com and I will provide correct attribution, or take it down, if the owner prefers.)
Thou shalt not kill.
Those four words are often used by opponents of self defense when they claim that divine law forbids the taking of another human life, even in defense of your own. So, how can a Christian justify the carrying of arms for self defense, or should they abhor such a practice and rely on divine intervention?
The first issue with the opening argument of this article is that it is the result of a mistranslation. While many Roman Catholic texts translate the fifth (sixth in some texts) Commandment as "you shall not kill", many other texts hold true to the original meaning of "you shall not murder." That is the key distinction.
In fact, when analyzing the issue using the Catechism of the Catholic Church, Part 3, Section 2, Chapter 2, Article 5 goes right to the heart of the matter.
§2263 The legitimate defense of persons and societies is not an exception to the prohibition against the murder of the innocent that constitutes intentional killing. "The act of self-defense can have a double effect: the preservation of one's own life; and the killing of the aggressor. . . . The one is intended, the other is not."
§2264 Love toward oneself remains a fundamental principle of morality. Therefore it is legitimate to insist on respect for one's own right to life. Someone who defends his life is not guilty of murder even if he is forced to deal his aggressor a lethal blow.
§2265 Legitimate defense can be not only a right but a grave duty for one who is responsible for the lives of others. The defense of the common good requires that an unjust aggressor be rendered unable to cause harm. For this reason, those who legitimately hold authority also have the right to use arms to repel aggressors against the civil community entrusted to their responsibility.
This tells us that not only do we have the right to use deadly force against those tho would try to take our own lives, but we have that right to defend others in our care as well. We all have a responsibility to each other individually, and those charged with the protection of the community (such as police officers) are justified using deadly force as well.
When you are forced to defend yourself to preserve your life, it is that act of preservation that is the intended result of the employment of force. You're trying to stop the aggressor. If the aggressor dies as a result of your meeting force with force, that outcome is considered unintentional by the church. You are trying to stop, not kill, though sometimes only the death of the attacker can halt the assault.
During the Last Supper, Jesus was preparing his followers for what was to come after he was gone. He told them, "one who has a money bag should take it, and likewise a sack, and one who does not have a sword should sell his cloak and buy one." (Luke 22:36). Once He, their shepherd, had left them, they would need to protect themselves, even if it meant selling their clothes to be able to buy a weapon to do so.
Some Christians are fond of saying "The Lord Will Provide," yet here is Jesus telling his disciples to provide for themselves, which would seemingly support Benjamin Franklin's 1757 quote in Poor Richard's Almanac, "God helps those who help themselves." What Jesus is really telling his followers is to prepare themselves using the tools God has provided in order that He might work His will through them.
If evil confronts a man in the form of an armed attacker, do we really expect God to strike the attacker down with a heart attack? Or is it more likely that He would provide "a defense for the needy in his distress" (Isaiah 25:4) through placing an armed, good man in the path of evil? If we are to believe that "the secret things belong to the LORD our God" (Deuteronomy 29:29), we cannot discount the idea that there are earthly ways in which God might intervene on our behalf.
But, how do we reconcile this with the Christian value of turning the other cheek? Again, the answer is in the text.
"When someone strikes you on (your) right cheek, turn the other one to him as well." (Matthew 5:39). What is being referenced in the text is not a deadly threat. You're not going to be killed by a slap to the face, and Jesus was urging the letting go of anger and pride.
Consider also Isaiah 2:4, "they shall beat their swords into plowshares and their spears into pruning hooks." Though this is often taken to mean that weapons should be destroyed now, what it is actually referring to in context is Judgment Day.
According to the Scripture, after the Final Battle between good and evil, God himself will rule the Earth and all forms of evil, vice, and sin will be gone. It is only after that time that weapons will no longer be needed for self-defense, and until then, we need to be prepared to act to preserve our own lives and the lives of others. It is the Christian thing to do.