It is curious that as academic interpretations of various tracts of the Bible are corrected, updated and improved, often and more usually the new or refined explanations seem never to be widely disseminated amongst the wider populace.

I had always understood from the Book of  Genesis, that God had struck down Onan, the second son of Judah, for "spilling his seed" (either by masturbating or by engaging in coitus interruptus.)  Onan, you might recall, sought to avoid making his wife, his deceased brother's widow pregnant by indulging in one of those solitary or self-centred practises whereby his seed went everywhere, save where it was supposed to. Had he not acted thus, by Ancient Custom the resulting first-born child would have been deemed to be that of his deceased brother. The medieval Roman Catholic Church went on (logically, upon the basis of the original interpretation) to argue that thereby contraception was against God's Will.

It appears that scholars of a theological vent, by putting these tracts from Genesis in their historical and cultural context, have decided that the story of Onan was much more likely to have been a warning against the breaking of the aforementioned Levirate marriage custom.  This 'new view' has been probably in the public domain for years but only recently, have I heard of it.  Well, there you go!  Yet another biblical tract taken out of context by the early Church and used to support dogma which has brought inadvertently distress to millions of people.

A moral argument might still be put forward reasonably to the effect that contraception is wrong but it should no longer be on the basis of the story of Onan. In consequence the theological argument against contraception (or masturbation or coitus interruptus) cannot have such weight, as had been formally the case.  On the evidence of what is said in Genesis with its modern interpretation, to use a Scottish legal turn of phrase, the case against contraception is 'not proven'.