On Gittin 9b the Gemara responds to attempts to add to a list of three similarities between gittin and shichrurei avadim that the list includes only d'rabanan matters but not d'oraisa. To this the Gemara asks that one of the similarities on the list is that shtarei erka'os are valid for all other shtaros except for gittin and shichrurei avadim. Then the Gemara asks (quoting from the point by point):

(n)Objection: A Get signed in the courts of Nochrim is Pasul mid'Oraisa, and this was counted!

(o)Answer: The case is, Yisrael witnesses saw it handed over. This is like R. Elazar, who says that Edei Mesirah Karsei (a Get is empowered by the witnesses that saw it given. Therefore, the Get is Kosher mid'Oraisa.)

Granted that the get is presumably valid according to Rabbi Elazar since the Eidei mesirah seem to be Jews. But doesn't the list state that "shtarei erka'os are valid for all other shtaros except for gittin and shichrurei avadim" -- according to Rabbi Elazar, it should not be valid for she'ar shtaros because it is considered mezuyaf mitocho! (Rabbi Abba's statement on 4a). How can the Gemara be ma'amid in the hava aminah that this list could be according to Rabbi Elazar if he would also pasul she'ar shtaros? Because Rabbi Abba's statement surely refers also to she'ar shtaros, for in its original context (Bava Basra 170a) it refers to a shtar in general, and not just Gittin, so it would be hard to answer something along the lines of "Since gittin require lishmah..."

Thanks in advance,

Shlomo Azrieli, New York, New York