In this post, I want to conclude my summary and discussion of Thomas’s reasoning about killing in self-defense by examining the objections to his position that he considers and his replies to those objections. (The first post is here; the article in the Summa is here.)

To review, Thomas’s position is that it is morally permissible to kill an assailant in self-defense, even when the assailed is not a public official or soldier, but only when it is necessary to preserve one’s life and only because the action that brings about the death of the assailant is a foreseen but unintended consequence of the action. In order to be morally licit, the lethal action taken in self-defense must not spring from an intention to kill the assailant; it can only spring from the intention to preserve one’s own life.

The first two objections Thomas considers attempt to put him at odds with Augustine. For Augustine says (in a letter) that “I do not agree with the opinion that one may kill a man lest one be killed by him.” And elsewhere (On Free Choice of the Will) an argument can be cobbled together for the same conclusion. Thus it appears that according to Augustine, Thomas is wrong.

Thomas’s reply is that in the letter in question (scroll down to section 5) Augustine does not contradict him because Augustine means only that “one may [not intend to] kill a man lest one be killed by him.” And this agrees with what Thomas has said: In defending my own life, I cannot intend to kill the assailant.

On the face of it, Thomas’s interpretation isn’t obvious to me. It’s true that a little later in the letter, Augustine says, “The precept, ‘Resist not evil,’ was given to prevent us from taking pleasure in revenge, in which the mind is gratified by the sufferings of others, but not to make us neglect the duty of restraining men from sin.” (This line of reasoning also summarizes Thomas’s reply to the fifth objection about a passage from Romans 12:19, which seems to prohibit self-defense.) The point Augustine makes suggests that the command to “resist not evil” is not given to prevent a man from acting with the intention of preserving his own life, but it doesn’t make that clear.

The second objection refers us to Augustine’s On Free Choice of the Will. (The relevant section is 1.5, which is one source of the famous phrase “an unjust law is no law at all.”) Here Thomas’s interpretation is that what Augustine really means (again) is that it is ultimately unlawful to defend one’s life (with lethal force) for the wrong reason, namely, with the intention of killing the assailant. On this point all I can say (again) is that I have read the relevant section of On Free Choice of the Will a number of times, and it isn’t obvious to me that Thomas’s interpretation is correct. Perhaps someone with more knowledge of this text can defend Thomas. I cannot. (In the first place, which one of the characters is presenting Augustine’s position? “Augustine” or “Evodius” or both? In the second place, the position that seems to stand is that the positive (human) law permits lethal self-defense even though those acting so in self-defense will be subject to a divine law.)

The third objection (which raises a question I was curious about before reading this passage) has to do with whether a cleric is permitted to remain a cleric after killing another person in self-defense. Thomas’s answer is no. This is because the question of “irregularity” (not adhering to the rule (regula) of Holy Orders) is not only a matter of intention but also of act. (I think the same distinction is present in Old Testament law in the distinction between “being guilty” and “being unclean.” Both are bad, but only the first involves intention.) Note that Thomas does not say whether the cleric’s irregular status is partial or total, perpetual or temporal. These further clarifications probably depend on circumstances.

The fourth objection is useful for clarifying Thomas’s point about the double effect of the act of self-defense. The objection is that since no one is morally permitted to fornicate in order to save his or her life, and since murder is a more grievous sin than fornication, so no one is morally permitted to do commit a more grievous sin than fornication, namely, murder, in order to preserve one’s life.

Thomas’s reply is that “The act of fornication or adultery is not necessarily directed to the preservation of one’s own life, as is the act whence sometimes results the taking of a man’s life.” This point is clear enough, I think. The idea is that the act of fornication is not “necessarily directed” to saving one’s life. Suppose a male assailant promises not to harm his female victim if she consents to have sex with him (putting aside questions of the legitimacy of such “consent,” which surely is not consent in this case.) Thomas’s point is that it wouldn’t be morally permissible for the victim to consent to this because the act of sex is not necessarily directed to letting her go. That is, whether her life is preserved depends ultimately not upon whether she consents to have sex but on whether the assailant chooses to let her go. This is unlike an act of self-defense (say, punching or shooting) which does not depend on a further action (choice) in order to secure one’s own life. The act of shooting that is done with the intention of preserving one’s life is the very same act that causes the assailant to die. So Thomas’s point is that the difference in the grievousness between murder and fornication is not relevant here. What is relevant is the connection between an act and its effect(s).

Print Friendly, PDF & Email

Posted by Gary Hartenburg


  1. Good posts, Gary. I’m pretty settled on the death penalty and “just war”, but not on “lethal self defense”. A lot to ruminate about here. It would be interesting to hear a debate betweeen Aquinas and Ted Nugent. :)


  2. I’d be curious to know whether your positions on the death penalty and just war involve any kind of double-effect reasoning and if so why double-effect reasoning wouldn’t be valid in cases of lethal self-defense.

    Also am enticed to start a new series: The Nuge Says.


  3. Gary, “The Nuge Sez”… oh yeah, do it!
    Insofar as I understand the double effect, my position on the death penalty is not on that basis. I believe it is a positive command and not a well intentioned but evil act with an unintended good side effect. It is to be premeditated and carried out specifically both for the good of the evildoer and for the sake of a good effect on the community. Self defense, if it is TRULY ONLY self defense and no other people stand to be harmed by the evildoer if I permit myself to be killed or maimed by him, I think is a Gospel call to the individual. If I am in the path of the evildoer doing harm to others, I do not think I have the same responsibility to the Gospel vis a vis the evildoer and his potential victims. My basis is essentially “community”. At least that’s where I’m at so far…


  4. I don’t see how the position you lay out on self-defense can be defended apart from consequentialist reasoning. For the reasoning depends on assessing whether others will be harmed in addition to myself, and that seems to be entirely a matter of counting the consequences. (I’m not a consequentialist, so this doesn’t sit well with me, but this isn’t the place to debate consequentialism.)

    On the relevance of community, it seems like I should take into account my contribution to the common good, too. If I let someone kill me, then the community loses my participation in it. That seems to harm the community (assuming I’m a good person) and should be avoided (within reason).


  5. Hi Gary, The problem I have with categorizing my view of the death penalty and self defense as “consequentialism” is, in light of the OT and God’s actions it’s tough to posit deontologically that all “killing” is wrong, though I would say that ontologically “death” is THE fundamental evil that God deals with through the Cross. In that sense I have a hard time categorizing my position neatly into one or another “moral philosophical box”. To be sure there are elements of consequences that must be taken into account, but they do not define the act itself ontologically as moral or immoral.

    Re: community, the martyrs contribute to the community BY their deaths (as did Christ, ultimately), so there’s that wrinkle.
    You’ve given me more stuff to think about. Thanks!


Leave a reply

Your email address will not be published. Required fields are marked *