Some elders came to St. Antony and asked him, “Which is the greatest of all virtues?” Each one then gave an opinion, some saying that “fasting and keeping of vigils” best help one come near to God; others said “voluntary poverty” and “detachment”; others said “compassion.” Last of all, Anthony gave his reply: “All that you have said is both necessary and helpful for those who are searching for God and wish to come to Him. But we cannot award the first place to any of these virtues; for there are many among us who have endured fasting and vigils, or have withdrawn into the desert, or have practiced poverty to such an extent that they have not left themselves enough for their daily sustenance, or have performed acts of compassion so generously that they no longer have anything to give; and yet these same monks, having done all this, have nevertheless fallen away miserably from virtue and slipped into vice.
What was it, then, that made them stray from the straight path? In my opinion, it was simply that they did not possess the grace of discrimination [discernment]; for it is this virtue that teaches a man to walk along the royal road, swerving neither to the right through immoderate [excessive] self-control, nor to the left through indifference and laxity. Discrimination is a kind of eye and lantern of the soul, as is said in the Gospel passage: ‘The light of the body is the eye; if therefore your eye is pure, your whole body will be full of light. But if your eye is evil, your whole body will be full of darkness’ (Matt. 6:22-3). And this is just what we find. For the power of discrimination, scrutinizing all the thoughts and actions of a man, distinguishes and sets aside everything that is base and not pleasing to God, and keeps him free from delusion…. Scripture also refers to it as ‘discernment’ without which we must do nothing—not even drink the spiritual wine that ‘makes glad the heart of man’ (Psalm 104:15), for it is said, ‘Drink with discernment’ (Proverbs 31:3), and ‘he that does not do all things with discernment is like a city that is broken down and without walls’ (Prov. 25:28). Wisdom, intellect and perceptiveness are united in discrimination; and without these our inner house cannot be built, nor can we gather spiritual wealth (cf. Prov. 24:3-4).… These passages show very clearly that without the gift of discrimination no virtue can stand or remain firm to the end, for it is the mother of all the virtues and their guardian.” (quoted by John Cassian in his Conferences)