The failure of this view of the custom of war, which is in its essence more opposed to Christianity than the custom of selling men for slaves or sacrificing them to idols, to take any root in men’s minds, is a misfortune on which the whole history of Europe since Erasmus forms a sufficient commentary. That failure is partly due to the unlucky accident which led Grotius in this matter to throw all his weight into the opposite scale. For this famous jurist, entering at much length into the question of the compatibility of war with the profession of Christianity (thereby proving the importance which in his day still attached to it), came to conclusions in favour of the received opinion, which are curiously characteristic both of the writer and his time. His general argument was, that if a sovereign was justified in putting his own subjects to death for crimes, much more was he justified in using the sword against people who were not his subjects, but strangers to him. And this absurd argument was enforced by considerations as feeble as the following: that laws of war were laid down in the Book of Deuteronomy; that John the Baptist did not bid the soldiers, who consulted him, to forsake their calling, but to abstain from extortion and be content with their wages; that Cornelius the centurion, whom St. Peter baptized, neither gave up his military life, nor was exhorted by the apostle to do so; that the Emperor Constantine had many Christians in his armies, and the name of Christ inscribed upon his banners; and that the military oath after his time was taken in the name of the Three Persons of the Trinity. One single reflection will suffice to display the utter shallowness of this reasoning, which was after all only borrowed from St. Augustine. For if Biblical texts are a justification of war, they are clearly a justification of slavery; whilst, on the other hand, the general spirit of the Christian religion, to say nothing of several positive passages, is at least equally opposed to one custom as to the other. If then the abolition of slavery is one of the services for which Christianity as an influence in history claims a large share of the credit, its failure to abolish the other custom must in fairness be set against it; for it were easier to defend slave-holding out of the language of the New Testament than to defend military service, far more being actually said there to inculcate the duty of peace than to inculcate the principles of social equality: and the same may be said of the writings of the Fathers. The different attitude of the Church towards these two customs in modern times, her vehement condemnation of the one, and her tolerance or encouragement of the other, appears all the more surprising when we remember that in the early centuries of our era her attitude was exactly the reverse, and that, whilst slavery was permitted, the unlawfulness of war was denounced with no uncertain or wavering voice.