We ought to learn the virtues through practicing them, not merely through talking about them, so that by acquiring the habit of them we do not forget what is of benefit to us. 'The kingdom of God', St. Paul says, 'resides not in words but in power' (I Cor. 4:20). For he who tries to discover things through actual practice will come to understand what gain or loss lies in any activity that he pursues..."
St. Peter of Damaskos (Book 1:A Treasury of Divine Knowledge, The Philokalia Vol. 3 pg. 183)