during fertile periods: "From this it follows that you consider marriage is not to procreate children, but to satiate lust." About the year 401, St. Augustine wrote "Of the Good of Marriage" in which he affirmed married couples have the option of having sex without either of them intending procreation: "For, whereas that natural use, when it pass beyond the compact of marriage, that is, beyond the necessity of begetting, is pardonable in the case of a wife, damnable in the case of an harlot; that which is against nature is execrable when done in the case of an harlot, but more execrable in the case of a wife." Saint Thomas Aquinas wrote in his Summa Contra Gentiles: "Hence it is clear that every emission of the semen is contrary to the good of man, which takes place in a way whereby generation is impossible; and if this is done on purpose, it must be a sin. I mean a way in which generation is impossible in itself as is the case in every emission of the semen without the natural union of male and female: wherefore such sins are called 'sins against nature.' But if it is by accident that generation cannot follow from the emission of the semen, the act is not against nature on that account, nor is it sinful; the case of the woman being barren would be a case in point." Protestant Reformers such as Martin Luther and John Calvin were opposed to unnatural birth control. Centuries later, John Wesley, the leader of the Methodist movement said that unnatural birth control could destroy one's soul. If the Manichaeans had an accurate idea of the fertile portion of the menstrual cycle, such knowledge died with them. Documented attempts to prevent pregnancy by practicing periodic abstinence do not appear again until the mid-19th century, when various calendar-based methods were developed "by a few secular thinkers". The Roman Catholic Church's first recorded official approval of periodic abstinence from 1853, where a ruling of the Church's Sacred Penitentiary addressed the topic. Distributed to confessors, the ruling stated that couples who had, on their own, begun the practice of periodic abstinence—if they had "grave reasons"—were not sinning by doing so. In the Catholic Church, a grave/significant reason for using NFP can include social, economical, medical and other analogous reasons that may motivate a couple to practise it to postpone pregnancy.