Why four ancient virtues are called cardinal, after the Latin word for hinge
Prudence, justice, courage and temperance earned the label cardinal from cardo, Latin for hinge, because every other good quality was thought to swing on them. Plato sketched the set, Aristotle worked it out in detail, and Stoics, Jewish thinkers and Christian theologians all kept returning to the same four.
The group existed long before anyone called it cardinal. In the Republic, Plato has his speakers agree that a good city must be wise, brave, temperate and just, and he maps each quality onto a class of citizens. Farmers and craftsmen need temperance to keep their appetites in check, soldiers need courage to stiffen their spirit, rulers need prudence to steer by reason, and justice sits above the other three, keeping their relationships in order. Plato ranked temperance, or sound-mindedness, as the most important of them all.
The Greek words carry shades English loses. Sophrosyne, usually rendered temperance, was often used about drinking and knowing when to stop before a fight broke out. Andreia, courage, is closely related to the word for an adult man and can also be translated as manliness. The Greek term for justice also meant righteousness, and prudence meant the practical skill of seeing what to do, when, and with what consequences.
Later writers bent the list to their purposes. Philo of Alexandria, a Hellenistic Jewish philosopher, read the same four into the words of Moses. Cicero, who lived from 106 to 43 BC, defined virtue as a habit of mind in tune with reason and nature, divided into the same parts. Seneca swapped courage for devotion when writing to console his mother, and Marcus Aurelius treated the virtues as the true goods to look for in oneself, rather than wealth or prestige.
Christianity absorbed the scheme. The four appear in the Book of Wisdom and in 4 Maccabees, and Ambrose, Augustine and Aquinas paired them with three theological virtues: faith, hope and charity. By 845 AD they were being painted in the Vivian Bible, one of the earliest European images of the set, now held in Paris.
Source: Cardinal virtues
