The fifth commandment, given in Exodus 20:13 is “You shall not kill.” Clearly this command addresses the evil of willfully taking the life of another or self by “killing the body” – as all human life is sacred. Additionally, we are not to “kill the soul,” of another under the same reason that all human life is sacred. Accordingly, to rightly consider this command means acknowledging all the ways we can do harm to another – both bodily and spiritually.
As the plain wording of the commandment shows, actions such as intentional homicide, suicide, every abortion (yes, even of those conceived in violence – as the unborn child is always innocent, with a right to life) and all acts of euthanasia are all intrinsically evil – as each of these acts is a willful killing of a human being. However, this command goes deeper – just as the dignity of every person is far more than simply being physically alive. For in this command, we are also called to give respect to others through avoidance of “scandal.” (In the Catechism of the Catholic Church, paragraphs 2284-2285 define scandal as “an attitude or behavior which leads another to do evil….Scandal takes on a particular gravity by reason of the authority of those who cause it or the weakness of those who are scandalized”). Scandal can be anything that weakens truth in the souls of others, leading them to sin or to turn away from faith. Examples are many (unfortunately) of those who cause scandal by words or acts which lead the innocent ones to commit sins that previously they had no intention or awareness to commit– such as when the youth are exposed to acts that are mortal sins by others who live such sinful ways – thus leading these “little ones” to sin (as Jesus refers to them in Matthew 18:6).
On a day to day level, this commandment places before us a stewardship of protecting all human life – including our own health and well-being. We are to eat right, seek proper care for ourselves, including in illness, and never willfully inflict harm upon ourselves or others. Likewise, we must be mindful that words can “kill,” when we speak in ways that cut down others, insulting them, or damaging their dignity (noting that while the 8th commandment will more fully apply to such sins, words do have the power to damage the lives of others). Finally, it is necessary that such interior attitudes or dispositions as resentment and unforgiveness breed death – as the love for a neighbor becomes deadened, leading to greater enmity between us and those whom we may resent, ultimately leading to separation from God (which is the definition of “hell”).
While the Catechism of the Catholic Church addresses the right to defend ourselves or others who cannot defend themselves from harm, it is important to keep in mind that such defense must not go beyond what is necessary to defend oneself or others from the harm that is being inflicted or threatened. Those with authority over peoples have a particularly grave responsibility to assure for such defense of peoples and to carry out such defense justly – which at times (unfortunately) can require the use of arms/weapons. However, when non-lethal ways can prevail, these should always be employed first and followed accordingly.
Thus, in this fifth commandment, it is important to keep in mind that we are to both never harm ourselves or others, and to preserve and build up the dignity of every human being, as is becoming of God’s plan for our eternal communion in heaven.
For further reading: In the Catechism of the Catholic Church, paragraphs 2258 - 2330 gives detailed teaching the Fifth Commandment, including in-depth treatment of what is referred to as the “just war” doctrine.