Front Sight, Press

“Without doubt one is allowed to resist against the unjust aggressor to one’s life, one’s goods or one’s physical integrity; sometimes, even ’til the aggressor’s death… In fact, this act is aimed at preserving one’s life or one’s goods and to make the aggressor powerless. Thus, it is a good act, which is the right of the victim.” [There are three conditions under which legitimate self-defense must lie:] “That he who is the target of the force is an aggressor and an unjust aggressor… That the object of the defense is an important good, such as the life, physical integrity or worthy goods… [and] That defensive violence is proportionate to aggression.” [Under these conditions,] “One is also allowed [not required] to kill other people’s unjust aggressor.”

Thomas Aquinas, Dizionario ecclesiastico (”Ecclesiastic dictionary”, UTET, 1959)