Mishnah vs. Baraisa — Eruvin 36b
תלמוד בבלי מסכת עירובין דף לו עמוד ב
אמר רב: ליתא למתניתין מדתני איו
Teshuvos Kol Mevaser () critiques the work of a Rabbi in
In the Introduction, the author cites our Gemara as an example of a tendency that Rav had to give precedence to a Tosefta over a Mishnah — since that is evidently what Rav is doing here. The author also cited Yevamos 83a, where Rav seems to even give precedence to a "non-Tosefta" Baraisa over a Mishnah. [Were this to be true, perhaps it could be seen as an extension of the concept of Rav Tanna u'Palig — Rav had the status of a Tanna, and therefore was entitled to dispute them (see Eruvin 50b).]
Kol Mevaser, however, rejects both examples.
In the first place, the Baraisa in Yevamos is a Tosefta – in the second chapter of Tosefta Bikkurim).
Moreover, Ido's Baraisa here is not a Tosefta!
Rather, states Kol Mevaser, it is only when there are two Baraisos that contradict a Mishnah — as is the case in our Gemara (see Tosafos to Yoma 54b d.h. Mai Shnah who define this principle; see also there that it is uniquely Rav's, and that others do not necessarily agree) — or a case in which there is some unique reason to prefer the Baraisa (as is the case in Yevamos 83b) that Rav gives the Baraisa precedence.