The Legal and Theological Background of Summa Theologiae II-II, q. 64, a. 7

QUESTION 64, ARTICLE 7 of the Secunda secundae of Saint Thomas Aquinas’s Summa theologiae, on “whether it is licit for someone to kill another in defending himself,” has been the focus—or, at least, the starting point—of countless articles and books over the past several decades. Notwithstanding the great attention paid to the article, there remains much disagreement regarding how it is to be understood. The present essay proceeds on the assumption that understanding the intellectual context within which Thomas was writing—taking into account especially the works he cites in the article—enables us to come to reasonable conclusions regarding what he meant in making various points.

Offered first of all, in section I of the present essay, is a translation of the corpus of the article, followed by some brief remarks on the various parts (and subparts) of its argument. More extensive remarks upon this main argument will be found in subsequent sections, the initial concerns of which are typically the article’s objections, Thomas’s responses, and the authorities he cites. Section II considers objection 1 and ideas that Thomas found in St. Augustine’s Letter 47 to Publicola. Section III considers objection 2 and ideas that he found in Augustine’s De libero arbitrio. (This section is rather lengthy; but the discussed arguments from De libero arbitrio, which are complex and subtle, are extremely useful in understanding Thomas’s own complex attitude toward self-defense.) Section IV moves away briefly from the article and considers what Thomas says about intention earlier in the Summa theologiae and in a passage in the Quaestiones disputatae De veritate. Section V considers Thomas’s responses to objections 1, 2, and 4 and what they tell us about the intention to defend oneself. Section VI, also rather lengthy, begins with a consideration of objection 3 and Thomas’s response, in both of which what is at issue is whether a cleric can kill another in self-defense, as discussed in a letter written by Pope Innocent III. Close attention to this letter helps one to understand how Thomas regards licit self-defense as effected by a private individual and noncleric. Section VII considers the final part of the corpus of the article, where Thomas says that public officials might licitly intend to kill but adds that they ought not to be moved by personal animosity. It considers also objection 5 and Thomas’s response, which also deal with personal animosity.

I. STh II-II, q. 64, a. 7

The following is a fairly literal translation of our article, dividing it into parts and subparts for easy reference:¹

• {1a} Nothing prohibits there being two effects of a single act, only one of which is intended [in intentione], the other being beside the intention [praeter intentionem]. {1b} Moral acts, however, take their species with respect to what is intended, not from that which is beside the intention, since this is per accidens, as is made clear above.² {1c} So, from the act of someone who defends himself there can follow a double effect: one, the conservation of one’s own life; the other, killing of the aggressor. {1d} Such an act, therefore, in so far as what is intended is the conservation of one’s own life, does not have the character of the illicit, for it is natural to whatever thing to conserve itself in being as far as possible.

• {2a} It is possible, however, for some act proceeding from a good intention to be rendered illicit, if it is not proportionate to the end. {2b} So, if someone in defending his own life uses more force than is called for, the act will be illicit. {2c} If, however, he should repel a force moderately, the defense will be lawful, for, according to law, it is licit “to repel force by force,” provided it is “with the moderation of blameless self-protection.” {2d} Nor is it necessary for salvation that a man omit an act of moderate self-protection so as...