We picked up on page 133 of the text where St. Isaac begins to describe Purity of Heart. Through guarding the mind and the senses, one can achieve a level of purity, but it is often fleeting because of our tendency to return to our sins through repeated exposure to that which is impure in the world. Lasting Purity of Heart is achieved only through affliction; since deep and prolonged affliction leads us to let go of our attachment to the world and ourselves and cling to God alone who is our life.
In the struggle for purity, fear precedes love. Obedience to God and the practice of virtue is its beginning. Eventually the love of God incites us to desire the doing of good. Spiritual knowledge comes only after such virtue has been achieved.
Philokalia Ministries