Ubi Arcano Dei Consilio §35

³⁵ Thomas Aquinas, the Angel of the Schools, also discovered in this fact the very formula and essence of our belief, for he writes that a true and lasting peace is more a matter of love than of justice. The reason for his statement is that it is the function of justice merely to do away with obstacles to peace, as for example, the injury done or the damage caused. Peace itself, however, is an act and results only from love. ( Summa Theologica , II-II, Q. 29 Art. 3, Ad. III)