The cardinal virtues are four: courage, sound understanding, self-restraint and justice. There are eight other moral qualities, that either go beyond or fall short of these virtues. These we regard as vices, and so we call them; but non-spiritual people regard them as virtues and that is what they call them. Exceeding or falling short of courage are audacity and cowardice; of sound understanding are cunning and ignorance; of self-restraint are licentiousness and obtuseness; of justice are excess and injustice, or taking less than one’s due.
In between, and superior to, what goes beyond or what falls short of them, lie not only the cardinal and natural virtues, but also the practical virtues. These are consolidated by resolution combined with probity of character; the others by perversion and self-conceit.
That the virtues lie along the midpoint or axis of rectitude is testified to by the proverb, ‘You will attain every well-founded axis’ (Proverbs 2:9 LXX). Thus when they are all established in the soul’s three faculties in which they are begotten and built up, they have as their foundation the four cardinal virtues, or rather, Christ Himself. In this way the natural virtues are purified through the practical virtues, while the divine and supranatural virtues are conferred through the bounty of the Holy Spirit.
~St Gregory of Sinai