The Catholic Church is opposed to artificial contraception and all sexual acts outside of the context of marital intercourse. This belief dates back to the first centuries of Christianity. Such acts are considered intrinsically disordered because of the belief that all licit sexual acts must be both unitive (express love), and procreative (open to procreation). The only form of birth control permitted is abstinence. Modern scientific methods of "periodic abstinence" such as natural family planning (NFP) were counted as a form of abstinence by Pope Paul VI in his 1968 encyclical "Humanae Vitae". The following is the condemnation of contraception: