The Beatitudes in the Gospel of Matthew are promises, prizes, fundamentally in this life and in the future. They constitute what Thomas Aquinas explains as the "the happy life", "the blessed life".
The Beatitudes, as the Theologian explains, respond to the gifts, that is, to the desire for the good, which is the spirit. The beatitudes "do not respond to the desire for happiness" because it is a selfish desire, it is the desire of the soul.
One of the beatitudes of Matthew refers to the pacific people:
Blessed are the peacemakers, for they will be called children of God. Matthew 5:9
The theologian in his exposition of the beatitudes analyzes why do not respond to the virtues, that is to say, the virtuous life, or to the habits that generate the virtues.
Justice among with Prudence are the virtues proper of the reason.Justice is not all good, there is a higher instance to justice, the retitude, "Do unto others as you would have them do unto you" as Matthew 7:12 says, retitude is also known as the golden rule.
The purpose of justice is to maintain the friendship between men, or in other words justice is general friendship as Aristotle said, but retitude is friendship with those who by their situation of indefencion can not give us back our effort, golden rule is different, is universal or ethical friendship. Justice arises from the desire for happiness, Justice is a virtue, Rectitude instead is a perfection, a spiritual gift, and arises from the desire for the good.
Peace is a perfection, a spiritual gift. Justice is not a perfection, so peace can not be the fruit of justice. There is only peace where there is rectitude, justice is not enough. The goal of Rectitude is communion, or the common life.
Being the son of God is being a friend of the neighbor, only the righteous, those who live righteously gives birth to the peace, the peace is a fruit of the spirit (Galatians 5:22-23) This blessing reminds us the importance of always act on principles and the most important principle is the golden rule.