A Homily by Saint Augustine the Bishop
Peacemakers are all those that have peace within themselves. That is, those who have set all the passions of their souls in order. This they do by subjecting their passions to reason, namely, to the mind and spirit. Thus, by conquering their fleshly desires, they have made of themselves a little kingdom of God. In this kingdom, everything is ordered into an harmonious whole, by virtue of the fact that the element which is chief and pre-eminent in man (namely, mind or reason) ruleth, without resistance, over the elements which we have in common with the beasts. And in this fashion, the element of mind or reason, which is pre-eminent in man, is made subject to something pre-eminent to itself, namely, the Truth, even the Only-Begotten Son of God. For no one is able to govern except he be subject unto the higher powers. Now, herein we have set forth the peace which is given on earth to men of good-will. This is the life of one who is thoroughly and completely wise.
From a kingdom such as this, which is a state of complete peace and order, the prince of this world is cast out. For he is one that can rule only through perversity and disorder. When this peace hath been inwardly established and confirmed then whatever persecutions the prince of this world, who is now cast out, shall stir up from without, he only increaseth the glory which doth redound to God. For his unable to tear down anything in that which is so upbuilt. And by the failure of his machinations, he doth but make manifest the strength with which it hath been inwardly built. Hence it followeth : Blessed are they that are persecuted for righteousness sake, for theirs is the kingdom of heaven.