1) Lev 20:10 deals with adultery: “A man who commits adultery with a married woman, who commits adultery with his neighbour's wife, the adulterer and the adulteress shall be put to death”. There is no parallel verse outlawing relations between a woman and a married man. But if the Priestly Torah meant to ban polygyny – so the objection – would Lev 20 not have included precisely such a parallel prohibition? Perhaps. But one must ask oneself whether in banning polygyny P is likely to have made it a capital crime or even to have tarred it with the opprobrium of adultery. Had P's anti-polygyny legislation been more fervent, Jewish marriage might have taken a very different course. Moreover, those who read Lev 18:18 as banning not polygyny but the marriage of a man to his wife's biological sister are every bit as flummoxed by the omission of that incestuous union from chapter 20. Lev 18:18 simply has no counterpart in Lev 20. If anything, it is easier to explain the absence of a polygyny ban than an incomplete register of incestuous relations. After all, polygyny had not been frowned upon in early Israel as far as we know; and Lev 20 may represent a less radical position than Lev 18 (see further). We have therefore classified this argument as indeterminate.

2) Union between a man and his wife's sister could be inferred by analogy from verse 16 that prohibits union between a woman and her husband's brother.