Catholic teachings on sexual morality draw from natural law, Sacred Scripture and Sacred Tradition and are promulgated authoritatively by the Magisterium. Sexual morality evaluates the goodness of sexual behavior, and often provides general principles by which one is able to evaluate the morality of specific actions. Among the sins gravely contrary to chastity are masturbation, fornication, pornography, homosexual practices and artificial contraception. Besides being considered a grave sin, the procurement or assistance in abortion can carry the penalty of excommunication.