catholic.com/thisrock/1991/9107chap.asp
WHAT DOES the Bible say about contraception? “Nothing!” reply many today–including some Catholic theologians and biblical scholars. Yet traditional manuals of moral theology cite Genesis 38:6-10 as an argument against contraception. Does this passage have anything to offer on the question? Let’s look at the text:
"Judah got a wife named Tamar for his firstborn, Er. But Er, Judah’s firstborn, greatly offended the Lord, so the Lord took his life. Then Judah said to Onan, ‘Unite with your brother’s widow, in fulfillment of your duty as brother-in-law, and thus preserve your brother’s line.’
“Onan, however, knew that the descendents would not be counted as his; so, whenever he had relations with his brother’s widow, he wasted his seed on the ground, to avoid contributing offspring for his brother. What he did greatly offended the Lord, and the Lord took his life too.”
Onan was supposed to marry his deceased brother’s childless widow. This practice, known as the Levirate law (from the Latin levir, meaning “a husband’s brother”), was required by the Law of Moses (Deut. 25:5-10) and was intended to insure an unmarried brother would “raise up seed for the deceased brother that his name be not blotted out of Israel.”
The argument against contraception, specifically coitus interruptus, based on this passage used to be considered straightforward. In recent years, both Protestant and Catholic commentators have downplayed, if not outright rejected, the anti-contraception interpretation of this text. Their argument goes like this: Onan’s sin consisted solely in his abandonment of his familial obligations to his dead brother. Onan performed the act which bears his name because the child which might have resulted would have been counted as his brother’s, rather than his own–something Onan found intolerable.
The difficulty with this argument is that violation of the Levirate law was not a capital offense. If a man didn’t fulfill his obligations to his deceased brother’s wife, she was to take the matter to the elders, who would counsel him and try to persuade him to change his mind. If he persisted, the widow was to “go up to him and strip his sandal from his foot and spit in his face, saying publicly, ‘This is how one should be treated who will not build up his brother’s family!’” (Deut. 25:9).
While such a punishment might be embarrassing, it falls short of the death sentence Onan received for his act. This suggests he sinned not only by violating the Levirate law, but also by the way in which he did so. The kind of act he committed was so despicable that, in the Old Testament context, it was punishable by death.
John Kippley, in Covenant, Christ and Contraception (New York: Alba House, 1970, page 19), explains it this way:
“Onan went through the motions of the life-giving act but refused to accept the consequences. He withdrew in order that the act could carry no reproductive consequences . . . [H]e went through the motions of the Levirate covenant, but he denied the reality of that covenant.”
Catholic teaching regards marriage as a covenant which has as one of its constituent elements an openness to new life and the procreative good. Sexual intercourse involves a renewal of the marriage covenant. Contraceptive intercourse is a violation of that covenant because it acts directly against procreation, one of the basic goods of marriage.
By acting contraceptively, Onan robbed sexual intercourse of its life-giving meaning and acted against the good of his potential offspring’s life. Both his intent and his concrete actions were against life. As a result, Onan received the Old Testament penalty for his crime.
