Yevamot II 95: Who Renders Whom Forbidden?

The rabbis struggle with what we should do if a husband has intercourse with his mother-in-law.  Their examination takes a somewhat circuitous path.  At the beginning of our daf, the rabbis walk through who is forbidden to whom based on prohibited sexual relationships.  

One of the more interesting arguments winds its way back to the thoughts of beit Hillel and beit Shammai.  Before their betrothal, women are permitted to all men and men are permitted to all women.  After they have been married, the woman is forbidden to all men except for her husband. The man, however, is only forbidden to his wife's family members.  What does that teach us about the whom men choose to be with?  They could be with anyone, but they choose their own mothers-in-law?

The rabbis then discuss punishments.  It is necessary to determine the severity of a given prohibition. TO do this, the rabbis walk through numerous cases and question whether they should be considered light prohibitions, severe prohibitions, or regular prohibitions.  They note who is punished in relation to who has transgressed a prohibition.  Who disqualifies whom?  Part of this conversation touches on whether a punishment will last for a lifetime, or whether a punishment is temporary.