Chastity is the good habit of a man who gains self-mastery of his sexual impulses so he may conform his sexual thoughts and acts to the beautiful, holy and natural gift of conjugal love within the vocation of married life, a love that is unitive and open to the conception of children. Those who are not married are called to inward and outward purity, to preserve purity for the sake of God and to abstain from all sexual activity outside of marriage, being modest in word and dress. 

Opposing Chastity, is the vice of Lust by which a man has a disordered desire for sexual pleasure, leading him blindly and rashly engage in various sexual sins including masturbation, viewing of pornography, contraception, fornication, adultery, homosexual acts and other abhorrent sexual acts, and acts of immodesty (lewdness, sexually provocative clothing) which seek to arouse sexual lust in others.