Prior to the 20th century, three major branches of Christianity—Catholicism, Orthodoxy and Protestantism—including leading Protestant reformers Martin Luther and John Calvin generally held a critical perspective of birth control (also known as contraception). Among Christian denominations today, however, there is a large variety of views regarding birth control that range from the acceptance of birth control to only allowing natural family planning to teaching Quiverfull doctrine, which disallows contraception and holds that Christians should have large families. Roman Catholicism Background Many early Church Fathers made statements condemning the use of contraception including John Chrysostom, Jerome, Clement of Alexandria, Hippolytus of Rome, Augustine of Hippo and various others. Among the condemnations is one by Jerome which refers to an apparent oral form of contraception: "Some go so far as to take potions, that they may insure barrenness, and thus murder human beings almost before their conception." Augustine, in On Marriage and Concupiscence, states that whoever merely involving lust in intercourse without intending procreation, "although they be called husband and wife, are not; nor do they retain any reality of marriage, but use the respectable name [of marriage] to cover a shame. ... Sometimes this lustful cruelty, or cruel lust, comes to this, that they even use sterilizing drugs." The phrase "sterilizing drugs" (sterilitatis venena) was widely used in theological and ecclesiastical literatures to condemn any contraceptive acts and birth control. Augustine utilized the biblical story of Onan as a supporting text to denounce contraception. The Catechism of the Catholic Church specifies that all sex acts must be both unitive and procreative. In addition to condemning use of artificial birth control as intrinsically evil, non-procreative sex acts such as mutual masturbation and anal sex are ruled out as ways to avoid pregnancy. Casti connubii explains the secondary, unitive, purpose of intercourse. Because of this secondary purpose, married couples have a right to engage in intercourse even when pregnancy is not a possible result: {{Blockquote|Nor are those considered as acting against nature who in the married state use their right in the proper manner although on account of natural reasons either of time or of certain defects, new life cannot be brought forth. For in matrimony as well as in the use of the matrimonial rights there are also secondary ends, such as mutual aid, the cultivating of mutual love, and the quieting of concupiscence which husband and wife are not forbidden to