Prudence allows us to discern what is good in every circumstance and to choose the right means of achieving it. Prudence in the Christian sense is different to prudence in the pagan sense because the goal of the Christian life is different to that of paganism. Much of what is meant in the Christian sense involves having a child-like trust in God. Prudence cannot be taught by a set of rules. It is cultivated through the life of grace, study and experience.
Justice is to give what is due to God and neighbor. Without justice, no society can survive. It is inseparable from our calling to be children of God, loving with God the things that God loves.
Courage, like the other cardinal virtues, takes a new form in the Christian life. Although it is unlikely that most of us will do battle in the physical sense, we are called to fight the good fight. This battle against spiritual enemies often spills over into physical persecution. How do we cultivate Christian courage? By making small sacrifices, by cultivating friendships and by reading the lives of the saints and how they acquired courage.
Temperance is the virtue that moderates the sensitive appetite. Given the dignity of marriage and the deep roots of the sexual appetite, great caution is needed in order to avoid misusing the gift of human sexuality. But we live in a world that actively encourages gross immorality and facilitates this by means of technology.
In summary, a very helpful and practical introduction to the cardinal virtues.