(c. 1225-1274)

from Summa Theologiae: Whether One is Allowed to Kill Oneself


St. Thomas Aquinas, the Italian scholastic philosopher and theologian, and the principal theological authority within the Roman Catholic Church and progenitor of the tradition known as Thomism, was the son of an Italian count, related through his mother to the Hohenstaufen dynasty. At the age of five, Thomas was placed in the care of the monks at the Benedictine monastery at Monte Cassino to be educated as a monk and later to become abbot, but after eight years, political circumstances forced him to leave. He then studied in Naples. In complete opposition to his family’s wishes, he became involved in the Dominican order, finding its emphasis on intellectualism more suitable to his interests. In 1245, Thomas escaped the house arrest he had been kept under by his family to prevent him from joining the Dominican order. As a Dominican, he was sent to Naples, then Rome, and then Paris, where he studied under the German philosopher and theologian Albertus Magnus. Thomas then followed his teacher to Cologne, where he was reluctantly appointed to be magister studentium. Thomas returned to the University of Paris to study for a master’s degree in theology in 1252 and was named master of theology in 1256. He wrote prolifically until December 1273, when a visionary experience changed him. When his secretary asked him why he had ceased to write, he said, “All that I have written seems to me like so much straw compared to what I have seen and what has been revealed to me.”

Thomas was greatly influenced not only by the Christian tradition but also by the works of Aristotle, which, preserved since antiquity in Arabic libraries, had remained mostly unknown in the Latin West until the end of the 12th century. In what is recognized as Thomas’s most important work, Summa Theologiae (1266–1273), he attempts to integrate Aristotelian thought with Catholic doctrine and to clarify many points of doctrine by synthesizing faith and reason into a coherent whole. Thomas believed that divine revelation and human reason were both aspects of the same uniform truth and that they could not conflict with one another; reason can discover some theological truths by observing the effects of God’s work in the world, yet the role of reason is limited, and faith is necessary to understand and believe what is unknowable by reason alone. Thomas also wrote a series of commentaries on Aristotle and the Bible, as well as Summa contra Gentiles (1260), a manual of concise arguments in defense of Church doctrine for use by missionaries attempting to convert Muslims and Jews.

Thomas often traveled between France and Italy, and on March 7, 1274, just a few months after his visionary experience, while en route to Lyon, he became ill and died at the Cistercian abbey of Fossanova. He was canonized in 1323 and proclaimed doctor of the church in 1567; he is often known as the Angelic Doctor.

The following selection is taken from the Summa Theologiae, 2a2ae, question 64, article 5. In this work, Aquinas begins each article by stating the reverse of his conclusion and the objections to a particular claim (“it appears that . . .”), then responds with a statement of the correct conclusion and the rebuttal to each of the previous objections in turn. In Question 64, article 5, Thomas argues against the legitimacy of suicide, incorporating the arguments of both Aristotle (referred to as “the Philosopher”) and Augustine. Thomas’s central argument appeals to Augustine’s inclusive interpretation of the Biblical commandment “Thou shalt not kill”: since there is a prohibition against killing human beings and suicide is killing a human being, suicide is therefore a sin, to which Thomas adds three further reasons: an argument from the natural inclination to live, an argument based on social community, and the argument that life ought not be rejected because it is a gift from God.


Thomas Aquinas, Summa Theologiae 2a2ae, question 64, article 5, tr. Michael Rudick. Quotation in introduction from Angelico Ferrua, S[ancti] Thomae Aquinas vitae fontes praecipuae (Alba, IT: Edizioni domenicane, 1968, p. 318).


from SUMMA THEOLOGIAE, 2A 2AE, Q. 64, A. 5


We proceed to the fifth article.

1. It appears that one is permitted to kill himself.  Homicide is a crime in that it is contrary to justice, but, as proven [by Aristotle] in Ethics, Book V, no one can do an injustice to himself; therefore, no one sins by killing himself.

2. Moreover, those with public authority are allowed to kill criminals; but sometimes one with public authority is himself a criminal, and so he is allowed to kill himself.

3. Moreover, it is permissible to submit oneself voluntarily to a smaller danger in order to avoid a greater, as one may amputate an infected member in order to save the whole body.  Sometimes one may, by killing himself, avoid a greater evil, such as a wretched life or corruption through some sin; therefore, it is permissible for one to kill himself.

4. Moreover, Samson killed himself (Judges xvi), yet he is numbered among the saints, as is evident from Hebrews xi.  Therefore, it is permissible for one to kill himself.

5. Moreover, it is said in II Maccabees xiv that a certain Razis killed himself, “choosing to die nobly rather than be subject to sinners and to injuries unworthy of his birth.”  Therefore, it is not unlawful to kill oneself.

On the contrary is what Augustine says in Book I of The City of God:  “We understand the commandment ‘Thou shalt not kill’ to pertain to man.  Kill no other man, nor yourself; for he who kills himself kills another man.”

I respond by saying that to kill oneself is altogether unlawful for three reasons.  First, because every thing loves itself, it is thus proper for every thing to keep itself in being and resist decay as far as it can.  Therefore, to kill oneself is contrary to natural inclination, and contrary to the charity according to which everyone ought to love himself.  Hence self-killing is always a mortal sin, inasmuch as it stands against natural law and charity.

Second, because every thing that is a part belongs to a whole, every man is part of a community, and as such is of the community.  Therefore, he who kills himself injures the community, as is proven by the Philosopher in his Ethics, Book V.

Third, because life is a gift divinely given to man, and subject to the power of Him “who kills and makes to live.”  Therefore, he who deprives himself of life sins against God, just as he who kills another’s slave sins against the slave’s master, and just as he sins who arrogates to himself power over something not committed to him.  To God alone belongs the power over death and life, according to Deuteronomy xxxii: “I kill and I make to live.”

To the first [argument that suicide is permissible], it may be objected that homicide is not only a sin against justice, but is also a sin against the charity that everyone ought to have for himself; on that ground, self-killing is a sin with respect to oneself.  And with respect to the community and to God, it is a sin through its opposition to justice.

To the second, it may be objected that one with public authority may kill a criminal because he is empowered to judge him.  But no one is allowed to be the judge of himself, and so one with public authority is not allowed to kill himself because of some sin, although he is allowed to commit himself to the judgment of some other.

To the third, it may be objected that man is indeed lord of himself through his free will, and so may lawfully dispose of himself as far as what pertains to this life is concerned; that much is governed by man’s free will.  But the passage from this life to the other, happier one is not subject to man’s free will, but to divine power.  Therefore, it is not permissible for a man to kill himself in order to pass over into the happier life.  Neither, likewise, to avoid the present life’s miseries; the “ultimate” evil of this life, and the “most frightful,” is death, as the Philosopher shows in Ethics, Book III, and so to kill oneself to evade the other miseries of life is to assume a greater evil to avoid a less.  Neither, likewise, may one kill oneself on account of some sin committed; in that case one harms oneself as much as may be, by preventing the necessary time for penitence.  Besides, killing a criminal is not permitted except through the judgment of public authority.  Neither, likewise, is a woman permitted to kill herself to prevent another’s violating her; she ought not commit the maximal sin on herself, which is to kill herself, to avoid another, smaller sin (for it is no crime for a woman to be violated through force, without her consent, because “the body is not corrupted without the mind’s consent,” as Lucia said [Golden Legend, IV]).  And it is certain that fornication and adultery are less sins than homicide, especially self-homicide, which is the gravest of all because it injures the self to which is owed the greatest love.  And it is also the most dangerous, because there remains no time to expiate the sin through penance.  Neither, likewise, is one allowed to kill himself in fear of consenting to sin, for “we must not do evil in order that good come from it” [Romans iii 8], or to avoid evils, especially smaller and less certain ones, for it is not inevitable that one will in the future consent to sin; God is capable, whenever temptation arises, to free man from sin.

To the fourth, it may be objected that, as Augustine says in The City of God, Book I, “Neither may Samson be otherwise excused for crushing himself along with his enemies in the fall of the house, except that the Holy Spirit inwardly commanded this in order to perform a miracle through him”; and he gives the same reason for certain holy women who killed themselves in time of persecution, whose memory the church celebrates.

To the fifth, it may be objected that it is fortitude when one does not shrink from suffering death inflicted by another person, in the interest of virtue and the avoidance of sin; but when one kills oneself to avoid bad punishments, it has some appearance of fortitude, on account of which certain suicides are accounted to have acted bravely, Razis among them.  But this is not real fortitude, it is instead some weakness in a soul not strong enough to bear hardship, as is shown by the Philosopher in Ethics, Book III, and Augustine in The City of God, Book I.

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