“Any nation,” the present Pope has said, “so mad as to contemplate war would be guilty of monstrous homicide and almost certainly of suicide.” There is, it would seem, a tendency to meet any proposal for the prevention of war and the promotion of peace with the argument that there is such a thing as a just war, and to leave it at that. There is a danger here of relapsing into the laissez aller attitude described by M. Maritain as “using the eternal truths as a pillow to go to sleep on.” To restrict discussion to the question of whether there can be a just war in the abstract is to invite unreality.

“There is such a thing as a just war.” For this position we have a formidable array of authorities, if we are to pin our faith to authorities; a formidable array of arguments, if we choose to take reason as our guide. “There is such a thing as legitimate self-defence, as legitimately helping the injured even by offensive warfare.” A proper authority, a just cause, a right intention, these are, according to St. Thomas, the three prerequisites of the just war. Can they not often and easily enough be fulfilled? In theory perhaps; in the hypothesis of two isolated States, in an isolated point of time, with clear-cut and indisputable aggression or injury on the one side and the impossibility of any defence or redress other than by war on the other. Such a state of affairs, however, in the world of to-day is, to all intents and purposes, impossible.