The Church is both idealistic and realistic about war. On the one hand, “the Church [urges] prayer and action so that the divine goodness may free us from the ancient bondage of war” (CCC #2307).

Peter Kreeft

On the other hand, “insofar as men are sinners, the threat of war hangs over them and will so continue until the coming of Christ.” Therefore, “as long as the danger of war persists … governments cannot be denied the right of lawful self-defense once all peace efforts have failed” (Gaudium et Spes #79). The same moral standards apply to collective self-defense by nations as to self-defense by individuals.

No war is just in itself. War is a sinful and barbaric invention. It is murder on a mass scale. But the choice to go to war can be just, if it is necessary self-defense. The aim of a just war (that is, a just “going to war”) is peace. The aim is not taking lives but saving lives: the lives of the innocent victims of aggression. The end that makes a war just can only be peace.

The “traditional elements enumerated in what is called the ‘just war’ doctrine” are the following “strict conditions for legitimate defense by military force” (CCC #2309). Defense: As implied above, a just war cannot be aggressive, but only defensive, a response to aggression. (Interestingly, the Quran teaches the same doctrine to Muslims: “Allah hates the aggressor.”) Grave damage: “The damage inflicted by the aggressor … must be lasting, grave and certain.” Last resort: “All other means of putting an end to [this grave damage] must have been shown to be… ineffective.” Hope for peace: “There must be serious prospects of success” and the ultimate aim and intention must be not war but peace.

Not graver evils: “The use of arms must not produce evils and disorders graver than the evil to be eliminated. The power of modern means of destruction weighs very heavily in evaluating this condition. Rules of war: It’s not true that all’s fair in love and war. The mere fact that war has broken out does not mean that everything becomes licit between the warring parties.

There has been a tradition in the Church of principled Christian pacifism, as well as a tradition of “just war.” Church doctrine does not pronounce in a final and authoritative way on all moral questions, leaving many up to prudential human judgement. Pacifism — the refusal to bear arms — is not a requirement for Christians, nor is it forbidden. It is an honorable opinion.

Therefore, “public authorities should make equitable provisions for those who for reasons of conscience refuse to bear arms; these are nonetheless obliged to serve … in some other way.” (CCC #2311).

PETER KREEFT is a professor of philosophy at Boston College. This column is reprinted with permission from his book “Catholic Christianity: A Complete Catechism of Catholic Beliefs Based on the Catechism of the Catholic Church” (Ignatius Press, 2001).

Catechism 101

Injustice, excessive economic or social inequalities, envy, distrust, and pride raging among men and nations constantly threaten peace and cause wars. Everything done to overcome these disorders contributes to building up peace and avoiding war:

Insofar as men are sinners, the threat of war hangs over them and will so continue until Christ comes again; but insofar as they can vanquish sin by coming together in charity, violence itself will be vanquished and these words will be fulfilled: They shall beat their swords into plowshares and their spears into pruning hooks; nation shall not lift up sword against nation, neither shall they learn war any more.

Catechism of the Catholic Church, #2317