Even though Rebbi Yehudah derives this from a verse, there must be some
logical way to reconcile this ruling, or else Rebbi Yehudah would have found
a more logical way to explain the verse. What is the logic to suggest that
one has a greater obligation for damages of a Shor Tam than for damages of a
Shor Mu'ad?
In addition, when the Gemara earlier (42a) suggests that the owner of a Shor
Tam is Chayav for Demei Vlados while a Mu'ad is Patur, Rava challenged the
suggestion, saying that it is senseless, since the laws of Tam are more
lenient than the laws of Mu'ad. What is the logic to explain Rebbi Yehudah's
ruling?
(a) The ME'IRI, cited by the Shitah Mekubetzes, explains that since people
know about a Shor Mu'ad, the obligation to avoid its damage falls equally on
the people that were damaged; they are responsible to stay out of its way.
Since the Nizak bears some of the responsibility, the Torah exempts a Mu'ad
in a case of "Shemirah Pechusah."
According to this logic, why should a Shor Mu'ad not be Patur even if the
owner was not guarding it all? The answer is that certainly if the owner let
the Shor out in the first place by not guarding it, he is responsible for
the Shor's action. However, if he guarded it in a way that would normally
prevent it from causing damage, but an Ones occurred, such as a Ru'ach
she'Eino Metzuyah, which allowed the Shor to escape, then since there is an
element of Ones involved, he should not be more Chayav to prevent it from
damaging than the person who was damaged.
This argument cannot be used to justify why the owner of a Shor Tam should
pay Demei Vlados while for a Mu'ad he is Patur, and that is why the Gemara
earlier considers that to be illogical.
(b) According to the opinion that holds that Chatzi Nezek is a Kenas, since
the Torah is obligating the owner for something for which he does not carry
full responsibility, anytime that a Shor Tam damages it should be no
different when the owner guards the Shor with a "Shemirah Pechusah." The
Torah can obligate a person to pay a Kenas for something that he does not
bear full responsibility for, as a penalty. However, if he guards the Shor
with a "Shemirah Me'ulah," and the damage is entirely beyond the control of
the owner, then the Torah does not impose a Kenas.
According to the opinion that holds that Chatzi Nezek is Mamon, the Torah
only required that the owner of a Tam pay Chatzi Nezek because "the Torah
had mercy on the owner," since he is not entirely at fault (since people do
not expect the Shor to do damage when it is a Tam, as the Gemara says on
15a). Accordingly, perhaps in exchange for being more lenient with the
person with regard to the amount of payment, the Torah was more stringent
with a person with regard to the circumstances that can cause him to be
Chayav. That is why he must pay even if he guards it with a "Shemirah
Pechusah." (M. Kornfeld)
This argument will not suffice to obligate the owner of a Shor Tam to pay
Demei Vlados, since the Chiyuv of Demei Vlados has nothing to do with a lack
of guarding it on the part of the owner. That is, the Chiyuv has nothing to
do with teaching him to guard his Shor better. The Torah is only Machmir in
order to ensure that the person does not take lightly the damages of his
Shor.
According to both of these answers, why should Rebbi Yehudah rule that one
pays for the Tzad Tamus of a Mu'ad when it damages after being guarded with
a "Shemirah Pechusah," like Rav Ada bar Ahavah rules? According to the
Me'iri, we should be lenient even with regard to the Tzad Tamus, since
people know to be aware of the Shor! According to the second answer, we
should also be lenient with regard to the Tzad Tamus, since it certainly is
not a Kenas (see Gilyon ha'Shas here), and, since we are not lenient with
regard to paying Chatzi Nezek in the case of a Mu'ad, there is no need to
have a reciprocal Chumra to be Mechayev the owner in a case of "Shemirah
Pechusah!" The logical arguments that we have presented would seem to
support the opinion of Rav (beginning of 46a) who argues with Rav Ada bar
Ahavah and maintains that Rebbi Yehudah exempts even the Tzad Tamus of a
Mu'ad (as the PNEI YEHOSHUA points out).
Apparently, according to Rav Ada bar Ahavah, since the Torah already was
Machmir for a Tam and required the owner to pay if it damages when guarded
with a "Shemirah Pechusah," the Torah did not remove that Chiyuv even when
the Shor became a Mu'ad. This was in order to prevent "Chotei Niskar," to
prevent the owner from benefiting as a result of allowing his Shor to gore
more frequently.