One of the Four Cardinal Virtues:
Justice is one of the four cardinal virtues. As such, it is a virtue that can be practiced by anyone, unlike the theological virtues, which are the gifts of God through grace. The cardinal virtues are developed and perfected through habit. While Christians can grow in the cardinal virtues through sanctifying grace, justice, as practiced by humans, can never be supernatural but is always bound by our natural rights and obligations to one another.
The Second of the Cardinal Virtues:
St. Thomas Aquinas ranked justice as the second of the cardinal virtues, behind prudence, but before fortitude and temperance. Prudence is the perfection of the intellect ("right reason applied to practice"), while justice, as Fr. John A. Hardon notes in his Modern Catholic Dictionary, is an "habitual inclination of the will." It is "the constant and permanent determination to give everyone his or her rightful due." While the theological virtue of charity emphasizes our duty to our fellow man because he is our fellow, justice is concerned with what we owe someone else precisely because he is not us.
What Justice Is Not:
Thus charity may rise above justice, to give someone more than he is rightfully due. But justice always requires perfect precision in rendering to each person what he is due. While justice is often used in a negative sense today—"justice was served"; "he was brought to justice"—the focus of the virtue is positive. While lawful authorities may justly punish evildoers, our concern as individuals is with respecting the rights of others, particularly when we owe them a debt or when our actions might restrict their exercise of their rights.
The Relationship Between Justice and Rights:
Justice, then, respects the rights of others, whether those rights are natural (the right to life and limb, the rights that arise because of our natural obligations to family and kin, the most fundamental property rights, the right to worship God and to do what is necessary to save our souls) or legal (contract rights, constitutional rights, civil rights). Should legal rights ever come into conflict with natural rights, however, the latter take precedence, and justice demands that they be respected. Thus, law cannot take away the right of parents to educate their children in the way that is best for the children. Nor can justice allow the granting of legal rights to one person (such as the "right to an abortion") at the expense of the natural rights of another (in that case, the right to life and limb). To do so is to fail "to give everyone his or her rightful due."