Aquinas

Aquinas seems to have acknowledged the inevitability of war, and so spends hardly any time on the sort of moral issues which affect us today (such as the bombing of civilians, the treatment of prisoners, the idea of a pre-emptive strike). In his Summa Theologica (2a2ae, 40.1-2) Aquinas asks a number of questions including “is it always a sin to wage war?”. He argues aginast Christian pacifism and such texts as Matt. 26.52, 5.39, Rom 12.19 with a summary of three criteria for just war (a development of Augustine).

• It must be undertaken only on the authority of God or the sovereign, “just as they use the sword in lawful defence against domestic disturbance when they punish criminals, as Paul says, “if you do wrong, be afraid, for he (the one in authority) does not bear the sword in vain” (Romans 13.4).” According to Paul, the proper constituted authority is an “agent of wrath” bringing judgement on the enemies of the state, and by implication, foreign powers who wish evil.
• It must be for a just cause. Of course we must define “just cause” and Aquinas does so in this way: “those who are attacked are attacked because they deserve it on account of some wrong they have done” (VIII.4).
• It must have a right intention, “they must intend to promote the good and to avoid evil” (VIII.5). Aquinas agreed with Augustine that desire for revenge, the desire to dominate are examples of immoral reasons for war.

Notice that Aquinas (following Augustine) takes a consequentialist approach. He is arguing that a war is justified if it has good consequences, such as the promotion of peace, increasing the good and decreasing an evil, or some appeal to “the common good”.

We need also to be clear that Aquinas set in motion a long-standing acceptance in the Roman Catholic Church of the legitimacy of war (as long as certain criteria were met). This tradition was continued into the present day, for example, by the Catholic Bishops conference in America in 1983 which gave further criteria for jus ad bellum (the just reasons for war) and jus in bello (the just ways of conducting war). This has had two main effects:

1. Challenges to militarism have come from non-Catholic Churches (such as the Quaker movement).
2. Churches such as the RC or Anglican churches have been ill-equipped to deal with the issues of war in a nuclear age raised by the bombing of Hiroshima and Nagasaki. These might be justified on utilitarian grounds, but are hard to justify on grounds of human rights or jus in bello.