What is the Gemara's question? It should be obvious that such a Chupah will
invalidate a woman from eating Terumah! The Mishnah records a Machlokes
Tana'im whether doing *Erusin* with a woman who is Pesulah l'Kehunah will
invalidate her from eating Terumah. According to Rebbi Meir, who rules that
it does, certainly Chupah should invalidate her from eating Terumah, since
Chupah follows Erusin!
It does not seem that Shmuel is permitting the woman to eat Terumah only
according to Rebbi Elazar and Rebbi Shimon of the Mishnah, who permit an
Arusah to eat Terumah. If that was his intention, why didn't Rami Bar Chama
(at the end of the Amud) simply say "Ein Chupah l'Pesulos," like Shmuel?
Instead Rami Bar Chama said "Just as the Tana'im of the Mishnah argue
regarding Erusin, they argue regarding 'Yesh Chupah l'Pesulos,'" implying
that according to Shmuel *all* the Tana'im of the Mishnah agree that Ein
Chupah l'Pesulos.
(a) RASHI (DH Yesh Chupah) explains that the Gemara is discussing a Chupah
*without* Kidushin (Kidushin is another word for Erusin). TOSFOS expands on
this and says that Rashi means that our Gemara follows the opinion of Rav
Huna in Kidushin (5a) who says that Chupah can be performed as a form of
Kidushin, just like "Kesef" and "Shtar." Why, though, should it have less
effect on the woman than normal Erusin? According to Shmuel, the way that
Chupah works and accomplishes Kidushin is by demonstrating "Kiruv Bi'ah" --
it shows that the man is beginning to bring the woman into his home and to
feel comfortable with her. This applies only to a woman to whom he is
permitted. Doing Chupah with a woman to whom he is prohibited, though, does
not accomplish anything, because it cannot be a sign of "Kiruv Bi'ah" if
Bi'ah is prohibited.
Even though the Gemara later (58a) applies Shmuel's ruling to a Chupah done
*after* Kidushin, that is because Shmuel holds that Chupah cannot accomplish
Nisu'in with a woman who is Pesulah l'Kehunah for the same reason it cannot
accomplish Erusin with such a woman. Even though she walks beneath the
Chupah, it will be as if nothing was done. Our Gemara, which is discussing
whether such a Chupah invalidates her from eating Terumah, must be referring
to a Chupah that is done in order to effect Kidushin (for otherwise the
Erusin already invalidated her), but the same would apply to a Chupah done
after Kidushin, with regard to whether or not she is considered a Nesu'ah
after such a Chupah.
(b) From Rashi's words, however, it does not seem that this is Rashi's
intention. Rashi later (58a, DH l'Rebbi Meir) cites the opinion that argues
with Rav Huna in Kidushin. Rashi writes that Chupah cannot be Koneh a woman
at all without Kidushei Kesef, Shtar, or Bi'ah, even when the woman is
completely permitted to marry the man and is not Pesulah. The RASHBA and
RITVA also assert that Rashi is *not* explaining the Gemara according to the
opinion that Chupah effects Kidushin, but rather Chupah can only effect
Nisu'in. This is also the understanding of the RAMBAM (Hilchos Terumos
7:21).
They question Rashi's explanation, though, and ask how Chupah that precedes
Kidushin can make the woman Pesulah? That Chupah does not effect anything!
The Rashba answers that even though Chupah is not Koneh in place of
Kidushin, nevertheless since she brought herself closer to Bi'ah Pesulah,
the Chachamim enacted (perhaps as a penalty, see Ritva) that she should be
prohibited her from eating Terumah. The Ritva, who considers this suggestion
as well, rejects it on logical grounds.
It could be, however, that Rashi is following his own opinion elsewhere,
that Chupah actually accomplishes something even when done before Kidushin.
What it accomplishes is that if Kidushin is later performed, it will not be
necessary to have another Chupah (as cited in Rashi's name by the HAGAHOS
MORDECHAI in Kidushin #546). Rashi hints to this view in Kidushin (10b, DH
Hechi Dami), as the RASHASH points out there.
Accordingly, the Gemara's question refers to when Chupah is done before
Kidushin. The doubt of the Gemara is that perhaps such a Chupah with a
Pesulah is *greater* cause (than Erusin with a Pesulah) to invalidate her
from eating Terumah, because the act of Chupah is closer to making her
Pesulah to Terumah (through Bi'ah). On the other hand, it might be *less*
reason to invalidate her, because it does not accomplish a "Kinyan" in and
of itself (i.e. without first effecting Kidushin), as opposed to Kidushin,
which is a Kinyan in and of itself. (Rashi later, 58a DH u'Shema Mina, when
discussing the opinion of Rav Sheshes, also alludes to the possibility that
Chupah with a Pesulah does not invalidate her from eating Terumah because it
cannot create Nisu'in altogether when the woman is not permitted to the
husband -- as Tosfos suggested, (a) above.)
(c) TOSFOS says that the Gemara is referring to a Chupah performed after
Erusin. The reason Shmuel says that even Rebbi Meir permits her to eat
Terumah is because he is referring to a case where the woman was *widowed or
divorced* after the Chupah but before the Bi'ah. Our Mishnah says that after
being divorced from Erusin, even Rebbi Meir agrees that she may continue to
eat Terumah. After being divorced from Nisu'in, even Rebbi Elazar and Rebbi
Shimon agree that she may *not* continue to eat Terumah. The Machlokes
between Rav and Shmuel is whether a divorce after the Chupah (but before
Bi'ah) is equivalent to a divorce during Erusin, or to a divorce during
Nisu'in. Rami Bar Chama compromises and says that according to Rebbi Meir,
who is more stringent, it is like a divorce from Nisu'in, but according to
Rebbi Elazar and Rebbi Shimon, who are more lenient, it is like a divorce
from Erusin.