@kbachler
- Onan
I thought you might mean the Leviticus chapter (15) you mentioned. I do not see how one can definitively say that chapter applies to contraception. It appears to apply to any emission of semen, whether in lawful intercourse or not. I am suggesting that contraceptive emissions would be a particular subset not dealt with in the chapter. I also suggest that the thought of it applying to coitus interruptus is nowhere to be found in that chapter.
To me, one cannot ignore the existence of the public humiliation remedy for a brother who shirks the law. That is the punishment, not the loss of life. It would also seem to be more in line with the ritual washings level of consequence, if you will, rather than death.
How else could he have “cheated” the law? Killing any babies? Not actually having intercourse & so refusing to raise an heir? Now that would be an interesting position vis-a-vis periodic continence, no? But the fact is, it is not that he refused to raise an heir, it is how he did it. It seems to me that option a, killiing any babies conceived, would be obviously wrong to everyone (at least for the Hebrews, not so much for their contemporaries). Option b, shamming the marrigage but not engaging in intercourse, would be so foreign to the culture as to be extremely remote, would be more work for no benefit to the surviving brother, and in any event would still provide some support for the widow, although, not, as noted, provide for a means of support in her later years. Therefore, I think the manner of the cheating of the covenant is part and parcel of the cheating or rejectiing of the covenant such that the two are really inseparable as the story is recounted.
“Here ends the detour into biblical reasons contra contraception. We now return to your regularly scheduled thread

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- As other posters have pointed out, I think, you have not addressed how the act of postponing intercourse causes, by the action of waiting and not through another mechanism, the subesquent act to be sterile. I submit that it does not. Hence there is no intentional alteration of the marital act.
Changing the timing and perhaps frequency of sex is not the same as changing the act. The act of intercourse remains the same. In the case of ABC, the couple is deliberately and by their own action rendering the act sterile. The NFP couple does not separate the unitive from the procreative parts of the act. They work with the body’s cycles, not against it. As this is how God created us, with both parts inseparably intertwined, it is licit to use periodic continence.