On 14b / 15a, the Gemara suggests that R' Meir might be learning from R' Chanina Sgan HaKohanim on the basis of a dorayta Av and a d'rabban vlad. If this is the case, it would be (from a dorayta point of view) a case of tamei vs tahor. It would, however, seem that the Mishna itself contradicts this becuase it confirms that Rabbi Akiva is "mosif". If Rabbi Akiva's case seems to be one of two dorayta tumot (which we used to prove that he holds ochel can transmit tuma dorayta). This seems like a smaller chiddush (tamei-tamei vs tamei-tahor), and therefore should not be "mosif".
Please help - what am I misunderstanding?
PS I'm also not sure why the Gemara here does not challenge the words "midivreihem" as they relat to an individual, seeming not in machloket with everyone else.
Marc Abrahams, Beit Shemesh, Israel
The Gilyon Hashas (14b on Tosfos DH "Hasam") points out that Tosfos in Zevachim (3a, DH "ha'Kosev") indeed holds that Rebbi Akiva is not adding a bigger Chidush, but rather adding a case (see also our Tosfos DH "Hasam," and Tosfos Yom Tov on the Mishnah).
As far as the word "mi'Divreihem" goes, it is possible that this is referring to all of the opinions which agree with this position. However, we specifically know about the words of Rebbi Chanina Segan ha'Kohanim, as Rebbi Meir's statement is said in the context of our Mishnah.
All the best,