 The Church teaches that sexual intercourse has a purpose; and that outside marriage it is contrary to its purpose.According to the "Catechism of the Catholic Church", "conjugal love ... aims at a deeply personal unity, a unity that, beyond union in one flesh, leads to forming one heart and soul", since the marriage bond is to be a sign of the love between God and humanity.Among what are considered sins gravely contrary to chastity are masturbation, fornication, pornography, homosexual practices, and artificial contraception.