The Fifth Commandment teaches that: “Thou shalt not kill” or more properly speaking: thou shalt not “do murder” (of oneself or another human being). The word “kill” is used too generally now blurring the difference between “killing” a human being and “slaying” an animal.
Of this Commandment the Catechism of the Council of Trent, edited by Saint Charles Borromeo and promulgated by Pope Saint Pius V, says:
It also forbids suicide. No man possesses such power over his own life as to be at liberty to put himself to death. Hence we find that the Commandment does not say: Thou shalt not kill another, but simply: Thou shalt not kill.
In the Summa Theologiae of Saint Thomas Aquinas (ST II-II Q. 64 a. 5) we find this questioned asked and answered:
Whether it is lawful to kill oneself?
Objection 1. It would seem lawful for a man to kill himself. For murder is a sin in so far as it is contrary to justice. But no man can do an injustice to himself, as is proved in Ethic. v, 11. Therefore no man sins by killing himself.
Objection 2. Further, it is lawful, for one who exercises public authority, to kill evil-doers. Now he who exercises public authority is sometimes an evil-doer. Therefore he may lawfully kill himself.
Objection 3. Further, it is lawful for a man to suffer spontaneously a lesser danger that he may avoid a greater: thus it is lawful for a man to cut off a decayed limb even from himself, that he may save his whole body. Now sometimes a man, by killing himself, avoids a greater evil, for example an unhappy life, or the shame of sin. Therefore a man may kill himself.
Objection 4. Further, Samson killed himself, as related in Judges 16, and yet he is numbered among the saints (Hebrews 11). Therefore it is lawful for a man to kill himself.
Objection 5. Further, it is related (2 Maccabees 14:42) that a certain Razias killed himself, “choosing to die nobly rather than to fall into the hands of the wicked, and to suffer abuses unbecoming his noble birth.” Now nothing that is done nobly and bravely is unlawful. Therefore suicide is not unlawful.
On the contrary, Augustine says (De Civ. Dei i, 20): “Hence it follows that the words ‘Thou shalt not kill’ refer to the killing of a man–not another man; therefore, not even thyself. For he who kills himself, kills nothing else than a man.”
I answer that, It is altogether unlawful to kill oneself, for three reasons. First, because everything naturally loves itself, the result being that everything naturally keeps itself in being, and resists corruptions so far as it can. Wherefore suicide is contrary to the inclination of nature, and to charity whereby every man should love himself. Hence suicide is always a mortal sin, as being contrary to the natural law and to charity. Secondly, because every part, as such, belongs to the whole. Now every man is part of the community, and so, as such, he belongs to the community. Hence by killing himself he injures the community, as the Philosopher declares (Ethic. v, 11). Thirdly, because life is God’s gift to man, and is subject to His power, Who kills and makes to live. Hence whoever takes his own life, sins against God, even as he who kills another’s slave, sins against that slave’s master, and as he who usurps to himself judgment of a matter not entrusted to him. For it belongs to God alone to pronounce sentence of death and life, according to Deuteronomy 32:39, “I will kill and I will make to live.”
Reply to Objection 1. Murder is a sin, not only because it is contrary to justice, but also because it is opposed to charity which a man should have towards himself: in this respect suicide is a sin in relation to oneself. On relation to the community and to God, it is sinful, by reason also of its opposition to justice.
Reply to Objection 2. One who exercises public authority may lawfully put to death an evil-doer, since he can pass judgment on him. But no man is judge of himself. Wherefore it is not lawful for one who exercises public authority to put himself to death for any sin whatever: although he may lawfully commit himself to the judgment of others.
Reply to Objection 3. Man is made master of himself through his free-will: wherefore he can lawfully dispose of himself as to those matters which pertain to this life which is ruled by man’s free-will. But the passage from this life to another and happier one is subject not to man’s free-will but to the power of God. Hence it is not lawful for man to take his own life that he may pass to a happier life, nor that he may escape any unhappiness whatsoever of the present life, because the ultimate and most fearsome evil of this life is death, as the Philosopher states (Ethic. iii, 6). Therefore to bring death upon oneself in order to escape the other afflictions of this life, is to adopt a greater evil in order to avoid a lesser. In like manner it is unlawful to take one’s own life on account of one’s having committed a sin, both because by so doing one does oneself a very great injury, by depriving oneself of the time needful for repentance, and because it is not lawful to slay an evildoer except by the sentence of the public authority. Again it is unlawful for a woman to kill herself lest she be violated, because she ought not to commit on herself the very great sin of suicide, to avoid the lesser sin; of another. For she commits no sin in being violated by force, provided she does not consent, since “without consent of the mind there is no stain on the body,” as the Blessed Lucy declared. Now it is evident that fornication and adultery are less grievous sins than taking a man’s, especially one’s own, life: since the latter is most grievous, because one injures oneself, to whom one owes the greatest love. Moreover it is most dangerous since no time is left wherein to expiate it by repentance. Again it is not lawful for anyone to take his own life for fear he should consent to sin, because “evil must not be done that good may come” (Romans 3:8) or that evil may be avoided especially if the evil be of small account and an uncertain event, for it is uncertain whether one will at some future time consent to a sin, since God is able to deliver man from sin under any temptation whatever.
Reply to Objection 4. As Augustine says (De Civ. Dei i, 21), “not even Samson is to be excused that he crushed himself together with his enemies under the ruins of the house, except the Holy Ghost, Who had wrought many wonders through him, had secretly commanded him to do this.” He assigns the same reason in the case of certain holy women, who at the time of persecution took their own lives, and who are commemorated by the Church.
Reply to Objection 5. It belongs to fortitude that a man does not shrink from being slain by another, for the sake of the good of virtue, and that he may avoid sin. But that a man take his own life in order to avoid penal evils has indeed an appearance of fortitude (for which reason some, among whom was Razias, have killed themselves thinking to act from fortitude), yet it is not true fortitude, but rather a weakness of soul unable to bear penal evils, as the Philosopher (Ethic. iii, 7) and Augustine (De Civ. Dei 22,23) declare.
Now to this we can add the teaching of the Catechism of the Catholic Church which makes the following important point:
Grave psychological disturbances, anguish, or grave fear of hardship, suffering, or torture can diminish the responsibility of the one committing suicide. (2282)
So this means that in the case of mental illness it is possible that the culpability of the sin, while still being indeed a sin, does not impute to the one who committed the sin the same punishment as one who did so with full knowledge. As the CCC (1857) teaches on the nature of mortal sin:
For a sin to be mortal, three conditions must together be met: “Mortal sin is sin whose object is grave matter and which is also committed with full knowledge and deliberate consent.” (RP 17 § 12.)
Thus one who does not have full knowledge of what they are doing and/or who does not deliberately consent to what they are doing (which when one is out of their mind they obvious cannot).
Also, depending on the method of suicide employed, it is possible that after committing the act that will ultimately cause their death there is a period of time, if brief, that allows for one to repent of their sin, and if they have perfect contrition for their sins they will not be lost.
There is an oft related story from the life of the Cure of Ars who found in his confessional a woman in tears who explained that her husband had just committed suicide by jumping off a bridge but the good Saint John Vianney, who could read hearts and was given knowledge about such things by God, said: “Between the bridge and the river he repented and was forgiven“.
Now certainly stories like this are accounts of exceptional graces, but it does mean that we can pray for the repose of the soul of those who have committed suicide. And as Saint Padre Pio tought we ought to pray that they had the grace of perfect contrition before they died because God is outside of time and we can still pray for them.
The best saint to pray to and to turn someone to for help if they are suffering from temptations of suicide is the great Saint Therese of the Child Jesus and of the Holy Face. It is not well known that she developed a deep understanding and love for those who suffer from these temptations during her final months because of the indescribable suffering she endured. Just a month before her death she said:
Watch carefully, Mother, when you will have persons a prey to violent pains; don’t leave near them any medicines that are poisonous. I assure you, it needs only a second when one suffers intensely to lose one’s reason. Then one could easily poison oneself. (August 30, Green Notebook).
During the process of her beatification one of her novices, Sr. Marie of the Trinity, said the following:
Three days before she died, I saw her in such pain that I was heartbroken. When I drew near to her bed, she tried to smile, and, in a strangled sort of voice, she said: If I didn’t have faith, I could never bear such suffering. I am surprised that there aren’t more suicides among atheists. (Proces de beatification et canonisation. Vol. 1 Proces informative ordinaire [Rome: Teresianum, 1973)] 472. English tr. in C. O’Mahoney, St. Therese of Liseux by Those who Knew Her: Testimonies from the Process of her Beatification [Dublin: Veritas, 1975] 254.)
O Blessed Little Flower of Jesus, thou didst desire upon earth to live for Jesus alone, to suffer for His sake, to make Him better known and love by all men. Now that thou rejoicest in the everlasting vision of that Holy Face, continue to send upon the World a shower of roses, the sweetness of whose perfume will draw all souls from the passing things of time to the joys that never end.
Obtain for our Holy Father the Pope, the favors of which he stands in much need; for our bishops, all things necessary to enable them to be true shepherds of the flock committed to their care;for our priests, a right understanding of their vocation and a burning zeal for souls; four our religious, the true spirit of their holy state; four our lay people, the gift of loyalty to Christ and His holy Church; for fallen Catholics, the grace to become again the friends of God; for non-Catholics, the light of the true faith and help to overcome the obstacles that are keeping them outside the One True Fold; for the foreign missions, zealous workers in those distant vineyards of the master. Obtain for us the grace to imitate thy “little way” that leads with certainty to the feet of Jesus, and beg for us those favors especially which we now confidently ask of thee (name any special favors).
These things we ask through thy love for the Child Jesus and the Holy Face.
O Little Therese of the Child Jesus, who during thy short life on earth didst become a mirror of angelic purity, of love strong as death, and of wholehearted abandonment to God, now that thou rejoicest in the reward of they virtues cast a glance of pity on us as we leave all things in thy hands. Make our troubles thine own and interceded for us to our Lady Immaculate, whose flower of special love thou wert, to that Queen of Heaven who “smiled on thee at the dawn of life.” Beg her as Queen of the Heart of Jesus to obtain for us the grace we yearn for so ardently, and to join with it a blessing that may strengthen us during life, defend us at the hour of death, and lead us straight on to a happy eternity.