In De Civitate Dei, book XIX chapter 27, Augustine of Hippo makes the following statement about the attainment of peace for individuals, and the justice that comes with this. The key is the obedience of man to God’s commands.
In this life, therefore, justice in each individual exists when God rules and man obeys, and when the mind rules the body and reason governs the vices even when they rebel, either by subduing them or by resisting them, while from God himself favour is sought for good deeds and pardon for offences, and thanks are duly offered to him for benefits received. 1
Augustine notes three main elements must be present for justice itself to be present in the individual: God ruling the man, the mind ruling the body, and the seeking of God for all one’s needs. Earthly peace is possible for the individual, but not absolute and perfect peace. Augustine goes on:
But in that ultimate peace, to which this justice should be related, and for the attainment of which this justice is to be maintained, our nature will be healed by immortality and incorruption and will have no perverted elements, and nothing at all, in ourselves or any other, will be in conflict with any one of us … God will hold sway over man, and the soul over the body, and in this state our delight and facility in obeying will be matched by our felicity in living and reigning. 2
The peace and justice which we seek and strive for in ourselves and in the world around us will be ultimately be perfected in the perfect rule of God in the future New Heavens and New Earth. “God will hold sway over man” and we will have perfect “felicity”.