This commandment states simply: You shall not kill. Its foundation, as always, is a positive value; in this case, the sacred and inviolable worth of every human life. The value of any human life does not lie in what it can produce, in the capacities it possesses, or in how far those capacities have been developed. The Catechism puts it clearly: “Human life is sacred because from its beginning it involves the creative action of God and it remains for ever in a special relationship with the Creator, who is its sole end. God alone is the Lord of life from its beginning until its end: no one can under any circumstance claim for himself the right directly to destroy an innocent human being” (Catechism of the Catholic Church, no. 2258).

Underlying this conviction are some affirmations from the Old Testament, which places categorical statements on God's lips: “Life and death (...) are from the Lord” (Sir 11:14). “For your own lifeblood I will demand an account (...) for in the image of God has God made mankind” (Gen 9:5–6).

And our Lord gives this commandment its full and demanding meaning. In the Sermon on the Mount, He says: “You have heard that it was said to those of ancient times, ‘You shall not murder;’ and ‘whoever murders shall be liable to judgement.’ But I say to you that if you are angry with a brother or sister, you will be liable to judgement; and if you insult a brother or sister, you will be liable to the council; and if you say, ‘You fool,’ you will be liable to the hell of fire. So when you are offering your gift at the altar, if you remember that your brother or sister has something against you, leave your gift there before the altar and go; first be reconciled to your brother or sister, and then come and offer your gift” (Mt 5:21–24). We can see that the precept not to kill goes beyond just safeguarding human life; it also means reverence and love for the person and their life.

It is clear that wilful homicide is a grave sin. But this commandment encompasses more complex aspects too. We can’t look at all of them in full detail, so we’ll limit ourselves to a few important points.

Abortion, euthanasia and suicide

From the very first moment of its existence (in other words, from conception) every human being possesses the inalienable right of every innocent person to life. It is not a mere cluster of cells or an appendage of the mother; he or she is a person. From the very beginning, its genetic code and programme for the future are already fixed. Its destruction cannot be cleaned up with euphemisms like “termination of pregnancy.” Direct abortion, whether chosen as an end in itself or as a means to an end, is a gravely wicked act. It carries several aggravating factors: its victim is the most innocent being imaginable, one who could never be considered an aggressor; it is defenceless, with absolutely no means of self-protection; it is put to death within the very place that should be the source of life; and it is the child’s own mother who decides or consents to its destruction.

The Church praises initiatives that support mothers in continuing with their pregnancies and underlines the importance of making clear the negative consequences of abortion. The role of the state in protecting this vulnerable population is crucial.

When Mother Teresa of Calcutta received the Nobel Peace Prize in 1979, she said something striking: “If we accept that a mother can kill even her own child, how can we tell other people not to kill each other? (...) We are fighting abortion by adoption — we have saved thousands of lives (...) Please don’t destroy the child; we will take the child.”

Another sensitive area is euthanasia. Euthanasia is the act of deliberately hastening death so that the patient does not suffer. Thinking in terms of the logic of love that Jesus Christ proposes, true mercy stands alongside those who suffer and helps them as much as possible... but does not seek to eliminate them. It is worth remembering that good intentions (like not wanting someone to suffer) are not sufficient to make a particular action good; the action itself must also be good (which deliberating ending a life is not).

The elderly, the terminally ill, and those suffering any reduction in their vital capacities are human beings deserving of the greatest respect, and they deserve to be cared for and helped to live as normal a life as possible. For the utilitarian mindset of practical materialism, such “diminished” persons look like an unbearable burden. Underlying this attitude is a culture that sees no meaning in suffering and no value in a life marked by pain. The teachings of our Lord stand in direct opposition to this outlook: He invites us to welcome those who suffer and to find redemptive meaning in human pain.

The Catechism explains that suicide “contradicts the natural inclination of the human being to preserve and perpetuate his life. It is gravely contrary to the just love of self. It likewise offends love of neighbor because it unjustly breaks the ties of solidarity with family, nation, and other human societies to which we continue to have obligations. Suicide is contrary to love for the living God” (no. 2281). A different matter entirely is choosing one’s own death in order to save another person’s life, which is a heroic act of charity.

Today, we understand that a person who takes their own life may be suffering such anguish, such emotional collapse, such disorder or panic, that their judgement is clouded, and the decision to end their life may lack full subjective responsibility (or that responsibility may at least be diminished), making the act difficult to impute to them morally. The Church, of course, prays for the salvation of those who die by suicide.

There is a story about another Teresa (this time St. Teresa of Ávila): one day she was praying for a loved one who had jumped off a bridge, and she started wondering whether she was doing something improper and unnecessary, until the Lord placed these words in her heart: Teresa, there are two seconds between the bridge and the water. Who but God can know what happened in that final moment?

Hatred and revenge

Moving from the realm of action to that of thought, we find that hatred (bitter resentment that wants others to come to harm and enjoys their misfortune) and revenge (seeking retaliation for wrongs suffered) also run contrary to love and reverence for other people’s lives. Our Lord is quite demanding on this point, because he calls us to love our enemies. Without divine help, this can seem impossible but, as St. Paul says, it is only possible to overcome evil with good (Rom 12:17).

For this reason, anger directed at people (typically at people who’ve wounded our pride or thwarted our interests) rather than at wrongful actions, is sinful anger. Lovingly keeping the 5th commandment means mastering hatred and rejecting every desire for revenge, imitating Jesus Christ.

Conclusion

Finally, it is worth noting that this commandment does not only forbid doing harm to another life; it also calls us to cherish both our own life and the lives of others. Christianity is life-affirming in the sense that it professes a love for life, this life on earth.

For those who believe in Jesus Christ, life is a gift each person has received. When life sometimes feels like a burden, it helps to remember what God tells us: “Before I formed you in the womb I knew you; before you were born I set you apart” (Jer 1:5). Life has a divine purpose, which God has known and loved from all eternity, and we are called to discover it and build it up through our freedom.

The value of each life lies in the love it is capable of giving. The capacity to love is the greatest gift we have received, and each of us is called to make it bear fruit in this life.