when the gmora says r yehudahs learning of an anusa, why does the gmora automatically assume that knaf doesnt include an anusa and must not mean that?
also why in the ond does r yehudah learn one smuchim from r yehoshua over the other? does he hold that you can only learn one thing from smuchim or what?
Reuven Kasierer, silver spring MD
The Chachamim learn that since all Arayos are dependent on "She'ar" (family relationship), without the Hekesh we would not know that "Anusas Aviv" is Asur (since there is no family relationship). The Chachamim explain "Kenaf" to mean "Shomeres Yavam Shel Aviv."
A Hekesh is not like a Gezeirah Shavah, and we need not learn everything one from another.