After discussing questions about killing plants, animals, and sinners by private citizens, public officials, and clerics, Thomas picks up the weighty and delicate subject of suicide. His position is that “it is altogether unlawful to kill oneself.” Thomas isn’t messing around here. He usually reserves language like “altogether unlawful” for serious purposes. And this is the only place in the eight questions about killing that he uses such strong language. Furthermore, Thomas usually considers only three objections to his position. On suicide, he considers five objections.
Whenever I discuss the morality of suicide with students, two considerations usually come up: The first is that a person can do whatever he wants with his own life—it’s his life after all; the second is that a person can commit suicide to avoid something bad, pain from terminal illness, for example, or even shame. Thomas addresses each of these points, and he throws in a discussion of Samson for good measure.
Before addressing these objections, let’s get clear about Thomas’s reasons for thinking it’s altogether unlawful to kill oneself. He’s got three reasons.
First, “everything naturally loves itself.” (Note the “naturally” and the “loves.”) This means that everything naturally strives to keep itself in existence. Thus, suicide is contrary to the “inclination” of nature and to “charity whereby every man should love himself.” The person who commits suicide not only violates the natural law but also does not love himself.
Second, since every person belongs to a community (Thomas actually says “the” community, that is, (I think) the community of human beings), and every person is considered to be a part of a community, a person who commits suicide injures the community by removing a part of it.
Third, God is the giver of life, so life is subject to God’s will. Thus, anyone who kills himself sins against God by taking something that does not belong to him. I think Christians are most familiar with this third line of reasoning. I won’t discuss this anymore.
Returning to the first two reasons: There have been those who doubted whether a person has a duty to himself. C. S. Lewis wrote (somewhere) that he thought, for example, that a person (like himself) who was learning to swim had a duty to himself also to teach himself to learn to dive even though diving was frightful. Kant wrote (somewhere) that a person had a duty to himself to develop his talents, abilities, etc.
But Thomas isn’t concerned with duties to oneself. His argument is about having charity toward oneself, loving oneself. (In fact, Thomas says that we each owe the greatest love to ourselves. This is in part because the person I am best able to love is myself.) And if you love something, then you want it to continue in existence. This brings up, tangentially, the question of what a person is because of course Thomas thinks that the death of the body is not the end of the person. So it must be that I need to love myself qua embodied person. Suicide (even attempted suicide) evidences a failure to love oneself as an embodied being.
In addition to the issue of loving oneself, there is also the consideration that individuals are not autonomous. They are intrinsically members of a community, and their community makes legitimate claims on them from which they cannot extricate themselves. If I kill myself, I harm my community because I am a part of it. I cannot simply choose to not belong to a community.
Thus, Thomas rebuts the consideration that a person commits no injustice in killing himself by arguing that he does act unjustly toward God and his community, and he undercuts the consideration about injustice by stating that justice is not the only relevant virtue—we must consider charity, too.
Now to the consideration that killing oneself is not lawful even if one does it to avoid some other bad thing. In the first case, if death is the greatest evil, then it makes no sense (says Thomas) to avoid a lesser evil by bringing on a greater one. And, in general, evil may not be done that good may come. In the particular case of committing suicide in order to avoid shame, Thomas says that this action is not courageous; it’s faux courage: “a weakness of soul unable to bear penal evils.”
And what about Samson, who killed himself in bringing down the pillars? The real difficulty is not that the Old Testament records Samson’s action but that Samson is listed among the men of faith in Hebrews. Thomas says Samson must have made that glorious list because the Holy Spirit “secretly commanded” him to bring the building down on himself (and everyone else). This kind of response will come up again in Thomas’s explanation of why Abraham was a good guy even though he was ready to kill his innocent son: Abraham was obeying God. (Note that Thomas does not try to excuse Samson on double-effect grounds. (If you don’t know what double effect is, we’ll get to that in the article on killing in self-defense.))
One last point about the seriousness of suicide. I noted at the start that Thomas takes suicide very seriously. This is because in killing oneself one has no time for repentance. If a person murders another person, the murderer at least has time to repent of his sin. Not so in the case of suicide. Thus, suicide turns out to be worse than murdering another person.