There is another aspect of the clerical control of peace and war in the interest of Christian unity which must not be forgotten.  The papacy sought to become an international tribunal.  The need for such a tribunal was as much a mediaeval as it is a modern commonplace.  Dante, who sought to vindicate for the emperor, rather than for the pope, the position and power of an international judge, has started the argument in famous words.  ’Between any two princes, of whom the one is in no way subject to the other, disputes may arise, either by their own fault, or by that of their subjects.  Judgement must therefore be given between them.  And since neither can have cognizance of the other, because neither is subject to the other, there must be a third of ampler jurisdiction, to control both by the ambit of his power.’[18] Such ampler jurisdiction, which might indeed be claimed for the emperor, but which he had never the power to exercise, was both claimed and exercised by the papacy.  The papacy, which sought to enforce the Christian canon of conduct in every reach of life and every sphere of activity, would never admit that disputes between sovereign princes lay outside the rule of that canon.  Innocent III, in a letter to the French bishops defending his claim to arbitrate between France and England, stands very far from any such admission.  ‘It belongs to our office’, he argues, ’to correct all Christian men for every mortal sin, and if they despise correction, to coerce them by ecclesiastical censure.  And if any shall say, that kings must be treated in one way, and other men in another, we appeal in answer to the law of God, wherein it is written, “Ye shall judge the great as the small, and there shall be no acceptance of persons among you.”  But if it is ours to proceed against criminal sin, we are especially bound so to do when we find a sin against peace.’[19] Here, in these words of Innocent, the clerical claim to control of peace and war touches its highest point.  In the name of a Christian principle, permeating all things, and reducing all things to unity, the dread arbitrament of war is itself to be submitted to a higher and finer arbitration.  The claim was too high to be sustained or translated into effect.  It is not too high to be admired.

Nor was it altogether remote from the actual life of the day.  Even to the laity of the Middle Ages, war was not a mere conflict of powers, in which the strongest power must necessarily prevail.  It was a conflict of rights before a watching God of battles, in which the greatest right could be trusted to emerge victorious.  War between States was analogous to the ordeal of battle between individuals:  it was a legal way of testing rights.  Now ordeal by battle was a mode of procedure in courts of law, and a mode of procedure whose conduct and control belonged to the clergy.  If, therefore, war between States is analogous to ordeal, it follows, first, that it is a legal procedure which needs a high court for its interpretation (and what court could be more competent than the papal curia?), and, next, that it is a matter which in its nature touches the clergy.  Such ideas were a natural basis for the Church’s attempt to control the issues of war and peace; and if we remember these ideas, we shall acquit the Church of any impracticable quixotism.