I answer that, From the very fact that a man desires a certain thing it follows that he desires to obtain what he desires, and, in consequence, to remove whatever may be an obstacle to his obtaining it. Now a man may be hindered from obtaining the good he desires, by a contrary desire either of his own or of some other, and both are removed by peace, as stated above. Hence it follows of necessity that whoever desires anything desires peace, in so far as he who desires anything, desires to attain, with tranquillity and without hindrance, to that which he desires: and this is what is meant by peace which Augustine defines (De Civ. Dei xix, 13) "the tranquillity of order."
Reply Obj. 1: Peace denotes union not only of the intellective or rational appetite, or of the animal appetite, in both of which consent may be found, but also of the natural appetite. Hence Dionysius says that "peace is the cause of consent and of connaturalness," where "consent" denotes the union of appetites proceeding from knowledge, and "connaturalness," the union of natural appetites.
Reply Obj. 2: Even those who seek war and dissension, desire nothing but peace, which they deem themselves not to have. For as we stated above, there is no peace when a man concords with another man counter to what he would prefer. Consequently men seek by means of war to break this concord, because it is a defective peace, in order that they may obtain peace, where nothing is contrary to their will. Hence all wars are waged that men may find a more perfect peace than that which they had heretofore.
Reply Obj. 3: Peace gives calm and unity to the appetite. Now just as the appetite may tend to what is good simply, or to what is good apparently, so too, peace may be either true or apparent. There can be no true peace except where the appetite is directed to what is truly good, since every evil, though it may appear good in a way, so as to calm the appetite in some respect, has, nevertheless many defects, which cause the appetite to remain restless and disturbed. Hence true peace is only in good men and about good things. The peace of the wicked is not a true peace but a semblance thereof, wherefore it is written (Wis. 14:22): "Whereas they lived in a great war of ignorance, they call so many and so great evils peace."
Reply Obj. 4: Since true peace is only about good things, as the true good is possessed in two ways, perfectly and imperfectly, so there is a twofold true peace. One is perfect peace. It consists in the perfect enjoyment of the sovereign good, and unites all one's desires by giving them rest in one object. This is the last end of the rational creature, according to Ps. 147:3: "Who hath placed peace in thy borders." The other is imperfect peace, which may be had in this world, for though the chief movement of the soul finds rest in God, yet there are certain things within and without which disturb the peace. _______________________
THIRD ARTICLE [II-II, Q. 29, Art. 3]
Whether Peace Is the Proper Effect of Charity?
Objection 1: It would seem that peace is not the proper effect of charity. For one cannot have charity without sanctifying grace. But some have peace who have not sanctifying grace, thus heathens sometimes have peace. Therefore peace is not the effect of charity.
Obj. 2: Further, if a certain thing is caused by charity, its contrary is not compatible with charity. But dissension, which is contrary to peace, is compatible with charity, for we find that even holy doctors, such as Jerome and Augustine, dissented in some of their opinions. We also read that Paul and Barnabas dissented from one another (Acts 15). Therefore it seems that peace is not the effect of charity.
Obj. 3: Further, the same thing is not the proper effect of different things. Now peace is the effect of justice, according to Isa. 32:17: "And the work of justice shall be peace." Therefore it is not the effect of charity.