Chapter 24 — Part II — The Beatitudes
Section 468. Q. Is not purity of heart the same thing as sincerity? A. Sincerity which feigns not any good dispositions foreign to the heart, but shows the really good dispositions of the heart by good deeds, is only the lowest degree of purity of heart. This last a man attains by constant and strict watchfulness over himself, driving away from his heart every unlawful wish and thought, and every affection for earthly things, and ever keeping there the remembrance of God and our Lord Jesus Christ with faith and charity.