The Apostle Paul speaks in his letter of living according to the flesh and of living according to the spirit. "Those who are in the flesh cannot please God", Romans 8: 8. Then Paul takes up the problem or the question of predestination: "For those God foreknew he  also predestined ...", Romans 8:29; and then conclude with the expression: "It is God that justifies" Romans 8:33.
The doctrine of Justification is central to the Christian faith and one of the causes of the schism between Catholics and Protestants. To speak of predestination is to speak of Justification, from the point of view of theology there is a destiny that is properly human and depends on our choices, and beyond a predestination product of the divine Providence, "Oh Father, you rule everything with providence ", Book of Wisdom 14: 3.
God from eternity predestines men, this is the idea from the scholastic philosophy and more properly Thomas Aquinas.
We can see the problem of justification from the general perspective of the letter to the Romans, that is, what means to live according to the flesh or to  live according to the spirit:
The concept of justification is related to the Parable of the Good Samaritan. There are two lifestyles: we live according to the flesh or live according to the spirit. We sin or live righteously, this is the message of the parable of the Good Samaritan, we help or we pass long.
This is so because there are soul and spirit in man. The soul is the first mobile motor, the perfection of the body as Aristotle teaches in his book About the soul, the author continues his explanation and tells us that the desire for happiness is the desire of the soul. Or to say we want to be happy for the existence of the soul. Happiness in this context would be a state of optimization or welfare of the faculties of the soul. But the desire for happiness is a selfish desire, in this context the neighbor does not matter. When we move through the desire for happiness we are living according to the flesh, forgetting the divine, the spirit. And it is here where the concept of justification arrives.
The justification is the gift or talent that allows us to go beyond our natural desire for happiness and start living according to God's desires: to live according to the spirit. The justification is a special help to act according to God's plan, "Be perfect, therefore, as your heavenly Father is perfect"( Matthew 5:48), reminds us Jesus Christ: perfect ourselves, improve ourselves, consider the neighbor, these are the keys to this new spiritual help. But remember to aquire wisdom we must before desire it. The spiritual gifts are no magic solutions.