This is a question I have asked myself a couple times in life – often coming to opposing conclusions depending on the scope of evidence I used, and the understanding of that evidence I was privy to at the time. Recently a manhunt for a murderer occurred in my neighborhood – putting many of my neighbors in a position of fear as the suspect was loose for over a day. As a co-captain of my neighborhood watch, I determined to set up a neighborhood outing for everyone (who desired) to go through Conceal Carry Weapons training together in order to get their carry permits from the State.
In other words – faced with an external threat to our neighborhood, I opted to arm us. The implication being, if the murderer came upon one of our neighbors, that neighbor would have the means to defend him/herself with deadly force. Simply because you can commit an action (by law, self-defense is legal justification for taking life), does not mean it is also moral to do so. In this case though, I am going to argue the moral justification for taking life in self-defense by examining nature, culture, history, legislation, philosophy, church doctrine, and scripture.
Let me start by stating reason should be used in discerning questions of good and evil. Humans have a mental capacity for discernment of morality. Whether you’re a stoic (like Marcus Aurelius) or a theist (like St. Paul), you most likely agree reason and teaching “is for the mature, who by constant use have trained themselves to distinguish good from evil.”