At times the post-quake man must forcibly defend his life and property and is thus compelled to dictate the fate of others. For the principles we must follow we need not look any further than Aquinas. We live in a world where libraries have burned to the ground and many of the old texts are gone forever. Here I will spare the reader of this treatise that tragedy and sum up Aquinas’ principle of double effect. Aquinas wrote that in defense of one’s self and property, one is justified in the killing of one’s assailant if and only if the killing of the assailant is necessary to the survival of one’s self. The killing of the assailant can only occur if the intention is to save one’s own life (or the life of his or her immediate community or property), and the amount of violence used against the assailant was the necessary amount and nothing more.
Based upon Aquinas’ principle, killing another as a means of self-defense isn’t necessarily prohibited. But the killing of another for reasons other than stated above is unlawful and unethical. The health of the social apparatus depends on this. Certainly it is obvious that warfare contains its own rules and codes that fall outside of the principle of double effect, though the principle of double effect does still, and always must, apply.