6th Commandment (In vitro Fertilization, Contraception, and Impure Thoughts)
The sixth commandment forbids all impure thoughts and desires, as well as any deliberate action undertaken to gratify them. This includes any kind of sexual sin, such as fornication, masturbation, pornography, rape, or homosexual relations. It also encompasses any use of contraception or in vitro fertilization, since these involve a deliberate attempt to thwart the procreative meaning of the sexual act.
The sixth commandment requires us to cultivate purity of thought and heart, and to avoid anything that might lead us into impurity. This includes not only obviously sinful acts, but also anything that might tempted us to sin, such as obscene literature or films, or even casual conversation about sexual matters.
The sixth commandment is a call to holiness, and it is only by the grace of God that we can hope to obey it. But it is also a call to happiness, for there is no true happiness to be found in impurity. By following the sixth commandment, we protect our relationships with God and with others, and we open ourselves up to the true joy that God has in store for us.