The Church's response to violence against Catholics, and indeed against any human being, is rooted in the fundamental principle of the sanctity of human life and the right to legitimate self-defense. While condemning violence, the Church recognizes that individuals and those responsible for others' lives have a right and sometimes a duty to repel unjust aggression, even if it means inflicting harm on the aggressor 1 2 3 4.

Legitimate Self-Defense

The Catechism of the Catholic Church states that "Love toward oneself remains a fundamental principle of morality. Therefore it is legitimate to insist on respect for one's own right to life" 3. This means that a person defending their life is not guilty of murder even if they are forced to deal a lethal blow to their aggressor 3. This principle is echoed by Pope Francis, who emphasizes that legitimate defense is not only a right but also a duty for those responsible for the lives of others 2.

Key aspects of legitimate self-defense include:

• Necessity and Moderation: The force used must be no more than what is necessary to repel the attack 1 2 5. If an aggressor can be stopped with less force, lethal force is unlawful 1 5 6. Saint Thomas Aquinas taught that an act of self-defense is unlawful if it is "out of proportion to the end" 2.
• Intent: The primary intention in self-defense should be to preserve one's own life and repel the attack, not to directly kill the aggressor 7. While some theologians have debated this point, the Thomistic doctrine holds that the self-defender's formal volition should be to preserve life and repulse the onslaught, with the aggressor's death being a foreseen but unintended consequence 7.
• Actual and Imminent Danger: The danger to oneself or another must be actual and imminent, not merely a future possibility 7 6. This teaching does not justify the use of force for reprisal or vengeance by private individuals, as that is a function of public authority 7.
• Defense of Others: It is lawful to aid another person to the same extent and within the same limits as are permissible for self-defense 5 6. For those responsible for others' lives, such as parents, spouses, soldiers, or police, defending those entrusted to their care can be a grave duty 2 6 4.

Defense of Property and Chastity

The Church also recognizes the right to defend property and chastity, even if it means taking the aggressor's life, provided the principles of necessity and moderation are observed 5 6.

• Property: While it is lawful to defend material goods, the property must be of considerable value, and charity forbids depriving a neighbor of life for a trivial loss 6. If stolen goods can be recovered without lethal force, it is unlawful to kill the thief 6.
• Chastity: Since chastity is considered a good of a much higher order than material goods, it is evidently lawful to defend it, even at the cost of the aggressor's life 6.
• Honor/Reputation: It is not lawful to kill someone to prevent an insult or attack on one's reputation, nor to avenge an insult already offered, as this would be revenge, not defense 6.

Aggressors Lacking Moral Responsibility

Even if an aggressor is not morally responsible due to a lack of reason (e.g., a lunatic or someone crazed with drink), it is still permissible to use force, including lethal force, if it is the only effective way to stop their onset and protect life or other comparable goods 7 4. In such cases, the fatal outcome is attributed to the aggressor whose action brought it about 4.

Summary

In summary, the Church's response to violence against Catholics is grounded in the right to legitimate self-defense, which can extend to the use of lethal force when strictly necessary to protect life, the lives of others, significant property, or chastity. This defense must always be proportionate to the threat, aimed at repelling the aggression rather than directly intending the aggressor's death, and exercised only when the danger is actual and imminent.