The Sin of Onan: contraception

"Onanism," the term derived from Genesis 38:9-10 which in traditional Christian usage has designated both masturbation and unnatural intercourse between a man and woman, is not exactly a pleasant theme to write about. And in a sense, that fact itself is the short answer to those who claim that these sorts of acts are ethically indifferent or innocent. In other words, the spontaneous negative emotional reaction of ordinary, decent people to such practices is really a "message" from the God who speaks to us in the still, small voice of our moral conscience.