The Gemara explains that the logic of the Machlokes is as follows. We know
that Dinei Nefashos (cases involving capital punishment) require Derishah
v'Chakirah mid'Oraisa. In court cases of Dinei Mamonos (cases involving
financial matters), even though the Torah also requires Derishah v'Chakirah
for such cases the Rabanan removed that requirement in order for people to
be more willing to lend money to those in need ("she'Lo Tin'ol Deles Bifnei
Lovin"). When the Tana'im argue whether a witness who testifies about the
death of a woman's husband needs Derishah v'Chakirah, they are arguing
whether permitting a woman to remarry is comparable to Dinei Mamonos, since
it involves giving the woman the money of her Kesuvah, or whether it is
comparable to Dinei Nefashos, since a woman who lives with another man while
her husband is still alive is Chayav Misah.
Why should testimony about a woman's husband (Edus Ishah) be comparable to
Dinei Mamonos just because of the Kesuvah? The primary subject of the case
is whether the woman may remarry or not; the Kesuvah is simply a secondary
consequence of the outcome of the case! Why should the secondary consequence
change the case into a case of Dinei Mamonos?
(a) The RAMBAN answers that when the Rabanan enacted the leniency that Dinei
Mamonos do not need Derishah v'Chakirah, they also wanted to be lenient with
regard to a woman's Kesuvah (which is also Dinei Mamonos). In order to be
lenient with regard to the Kesuvah, the Rabanan had to enact that we be
lenient with regard to the matter of the marriage as well, because the
Kesuvah stipulates that "*when she gets married to someone else*, she will
receive her Kesuvah." Hence, we are able to give her the Kesuvah only if we
permit her to get married. That is why the Rabanan permit her to get married
without Derishah v'Chakirah.
(Even though the reason they were lenient in all other Dinei Mamonos was
because of "she'Lo Tin'ol Deles Bifnei Lovin," which does not apply in the
case of a Kesuvah, the Rabanan still wanted to be lenient with the Kesuvah
in order not to differentiate between monetary laws ("Lo Plug"), or because
of "Chen" -- to help ensure that the woman will be dedicated to her
husbanded, knowing that it is easy for her to get her Kesuvah.)
(b) The RAMBAN suggests a second explanation. He says that on one hand, Edus
Ishah is not exactly like Dinei Nefashos, because the case involves whether
or not the woman may remarry, and not whether she is to be punished. On the
other hand, Edus Ishah is not exactly like Dinei Mamonos either, because the
subject of the testimony is the marriage, and not the Kesuvah. Therefore,
the question is to which type of case is Edus Ishah more similar?
Those who say that Edus Ishah does not need Derishah v'Chakirah maintain
that since today Dinei Mamonos are much more common than Dinei Nefashos (as
Beis Din does not rule on cases of Dinei Nefashos today), it is logical to
assume that the Rabanan said that we should treat Edus Ishah like Dinei
Mamonos, the more common type of court case (not just because of the
Kesuvah, but because we have to compare it to one of the two types of cases,
so we compare it to the more common type of case).
(c) The RITVA in the name of the RE'AH writes that *mid'Oraisa* Edus Ishah
does not need Derishah v'Chakirah. This is because the verse mentions the
requirement for Derishah v'Chakirah only with regard to Dinei Nefashos and
Dinei Mamonos, but not with regard to Edus Ishah. (The Gezeirah Shavah of
"Davar, Davar" (from Dinei Mamonos) does not apply to Edus Ishah to teach
that it needs Derishah v'Chakirah.)
Why, then, should anyone say that Edus Ishah requires Derishah v'Chakirah?
The Re'ah explains that the reason Edus Ishah should require Derishah
v'Chakirah is because mid'Oraisa the testimony for the *Kesuvah* really
needs Derishah v'Chakirah (since it is Dinei Mamonos), and the only reason
it does not need Derishah v'Chakirah is because the Rabanan enacted that
other Dinei Mamonos do not need Derishah v'Chakirah (because of "she'Lo
Tin'ol Deles..."). Therefore, they also applied that enactment, as a "Lo
Plug," to the Kesuvah. However, since this reason (for exempting the
testimony with regard to the Kesuvah from Derishah v'Chakirah) has a weak
basis, the Rabanan take advantage of any reason *to require* Derishah
v'Chakirah for the Kesuvah. Therefore, the Rabanan instituted Derishah
v'Chakirah for Edus Ishah because of its similarity to Dinei Nefashos, in
order that the testimony -- as it affects the Kesuvah -- have Derishah
v'Chakirah.
It seems that the Re'ah is following his opinion elsewhere. On 88a (see
Insights there), the Re'ah (cited by the Ritva) comes up with the novel
suggestion that a single witness is believed *mid'Oraisa* to testify about
the death of a woman's husband. The reason he is believed mid'Oraisa is
because if the witness is lying, his lie will become known sooner or later
through the return of the husband ("Milsa d'Avida l'Giluyei"). This supplies
sufficient grounds to assume that the witness is not lying, and he is
believed mid'Oraisa.
It seems that the Re'ah holds that a Rabbinic enactment is not sufficient
reason to allow us to accept the testimony of Edus Ishah, which involves
Isurim d'Oraisa. Therefore, the requirement for Derishah v'Chakirah *cannot*
be d'Oraisa for Edus Ishah, because if it was required mid'Oraisa, then the
Rabanan would not be able to be lenient and remove that requirement. (The
logic of "Milsa d'Avida l'Giluyei" is obviously not enough to exempt Edus
Ishah from the requirement of Derishah v'Chakirah, since the Gemara does not
mention that possibility here.)
(d) The RASHBA understands from the words of the RAMBAM (Hilchos Gerushin
13:28) that the Rambam has another answer to this question.
The Rambam writes that the reason Edus Ishah does not need Derishah
v'Chakirah is because the Rabanan were lenient due to their concern that
women do not become Agunos ("Hataras Agunah"). How can the Rambam give a
different reason than the reason the Gemara gives? The Gemara says that the
reason Edus Ishah does not need Derishah v'Chakirah is because it is
considered Dinei Mamonos, since it involves the Kesuvah!
The Rambam must mean that the Kesuvah does not make Edus Ishah into a case
of Dinei Mamonos. Rather, Edus Ishah is clearly Dinei Nefashos, since the
Beis Din is permitting an Eshes Ish to remarry. However, out of concern for
Agunos, the Rabanan instituted that since the Kesuvah introduces an element
of Dinei Mamonos into Edus Ishah, we may treat the entire case like Dinei
Mamonos, foregoing Derishah v'Chakirah. (Others explain the Rambam
differently; see footnote #109 to the Rashba.)