http://www.vatican.va/archive/ccc_css/archive/catechism/p3s2c2a9.htm
**[2516] Because man is a
composite being, spirit and body , there already exists a certain tension in him; a certain struggle of tendencies between “spirit” and “flesh” develops. But in fact this struggle belongs to the heritage of sin. It is a consequence of sin and at the same time a confirmation of it. It is part of the daily experience of the spiritual battle:
For the Apostle it is not a matter of despising and condemning the body which with the spiritual soul constitutes man’s nature and personal subjectivity. Rather, he is concerned with the morally
good or bad works, or better, the permanent dispositions - virtues and vices - which are the fruit of
submission (in the first case) or of
resistance (in the second case) to
the saving action of the Holy Spirit . For this reason the Apostle writes: "If we live by the Spirit, let us also walk by the Spirit."304
I. PURIFICATION OF THE HEART
**[2517] The heart is the seat of moral personality: "Out of the heart come evil thoughts, murder, adultery, fornication. . . . "305 The struggle against carnal covetousness entails purifying the heart and practicing temperance:
Remain simple and innocent, and you will be like little children who do not know the evil that destroys man’s life.306
**[2518 The sixth beatitude proclaims, "Blessed are the pure in heart, for they shall see God."307 “Pure in heart” refers to those who have attuned their intellects and wills to the demands of God’s holiness, chiefly in three areas: charity;308 chastity or sexual rectitude;309 love of truth and orthodoxy of faith.310 There is a connection between purity of heart, of body, and of faith:
The faithful must believe the articles of the Creed "so that by believing they may obey God, by obeying may live well, by living well may purify their hearts, and with pure hearts may understand what they believe."311
**[2519] The “pure in heart” are promised that they will see God face to face and be like him.312 Purity of heart is the precondition of the vision of God. Even now it enables us to see
according to God, to accept others as “neighbors”; it lets us perceive the human body - ours and our neighbor’s - as a temple of the Holy Spirit, a manifestation of divine beauty.
II. THE BATTLE FOR PURITY
**[2520] Baptism confers on its recipient the grace of purification from all sins. But the baptized must continue to struggle against concupiscence of the flesh and disordered desires. With God’s grace he will prevail
- by the virtue and gift of chastity , for chastity lets us love with upright and undivided heart;
- by purity of intention which consists in seeking the true end of man: with simplicity of vision, the baptized person seeks to find and to fulfill God’s will in everything;313
- by purity of vision , external and internal; by discipline of feelings and imagination; by refusing all complicity in impure thoughts that incline us to turn aside from the path of God’s commandments: “Appearance arouses yearning in fools”;314