1) THE DEFINITION OF "HE DID NOT KNOW" IN THE CASE OF DAMAGES
OPINIONS: Rava discusses a case in which a person entered someone's courtyard without permission and damaged the owner's property. Whether he caused damage deliberately or indirectly (for example, the owner tripped over him and was injured) he is obligated to pay. In contrast, if the owner damaged the trespasser, he is exempt from payment. Rav Papa qualifies this ruling with the condition that the owner is exempt only when he "did not know" about the trespasser. If "he knew" and damaged him, the owner is liable because the trespasser may say, "Even though you have permission to evict me from your property, you have no permission to damage me."
The Gemara points out that Rava and Rav Papa are consistent with their opinions expressed in another ruling (which is attributed to one of them; exactly who said it is the subject of dispute): When two people were in a place in which both had permission to be (for example, a public domain), or two people conducted themselves in a negligent way (for example, they were running in the public domain), if they damaged each other they are both liable. If, however, one was damaged by the other indirectly (for example, one stood still and the other tripped over him), they are exempt. The Gemara infers that when both are liable it is because both had the same status (both with permission or both without permission). If one had permission and the other did not have permission, the one who had permission is exempt and the one without permission is liable. RASHI (DH d'bi'Reshus) writes that the one with permission is exempt even if he damaged directly, as long as "he did not know" about the one who did not have permission to be there.
What does Rav Papa mean that "he did not know" about the trespasser, and how does his lack of knowledge affect the Halachah?
(a) RASHI (48b, DH Hiziku) explains that in the cases in which two people with the same status damaged each other, they are liable even if the damage was done accidentally, as long as the damage was done directly (see also Rashi DH v'Hizik). Rashi (DH Chayavin) explains that this is because in matters of damage it makes no difference whether the damage was done deliberately or not. (See the Gemara earlier (26b) which says that a person who damages is liable for accidental damage just as he is liable for deliberate damage.) When the Mishnah earlier (32a) exempts two people who damaged each other in the public domain, Rashi asserts that the wording of the Mishnah is imprecise and it does not refer to when they damaged each other directly. Rather, Rashi explains that the Mishnah means that they "were damaged by each other" indirectly (for example, one bumped into the other), because Rashi's position is that one who damages directly is always liable.
How does Rashi understand Rav Papa's statement that the owner is exempt for direct damage when "he did not know" about the trespasser? The LECHEM MISHNEH (Hilchos Chovel u'Mazik 1:16) understands that according to Rashi, Rav Papa means that the owner did not even see the trespasser before he damaged him. In such a case, Rashi agrees that he is exempt even if the damage was direct, since he did not even know that the damagee was there. Tosfos earlier (27b, DH u'Shmuel) seems to support the logic of Rashi's statement. Tosfos states that although the Gemara (26b) teaches that a person who damaged is liable even when he was an "Ones" (the damage he did was beyond his control), nevertheless if he was an "Ones Gamur" (an absolute "Ones") he bears no liability at all and is exempt. In the case of the Gemara here, Rashi understands that since the owner did not even know that someone was on his land, he is exempt from liability for any damage he caused to the trespasser. In contrast, if he knew someone was there, he is liable even if he damaged him unintentionally (and even if the damagee was there without permission), because he should have been more careful.
(b) However, the RAMBAM (Hilchos Chovel u'Mazik 1:16) understands the Gemara differently. He writes, "One who damages his friend deliberately anywhere is liable for [the] five forms of payment. Even if a person entered his property without permission and the owner damaged him, the owner is liable because he is allowed to evict him but he is not allowed to damage him. However, if the person who entered was damaged indirectly by the owner, the owner is exempt. If the owner was indirectly damaged by the trespasser, the latter is liable because he entered without permission. If both were there with permission, or both were there without permission, and they were indirectly damaged by each other, they are both exempt."
The MAGID MISHNEH and LECHEM MISHNEH explain that the Rambam understands Rav Papa's statement (that the owner is exempt only when "he did not know") differently from Rashi. The Rambam understands that Rav Papa means that the owner did not deliberately damage him (but not that he did not see him). The owner is liable only when he deliberately damages the trespasser, and in such a case he is liable even if the latter had no right to be there. When the Gemara (48b) states that when they were both there with permission they are exempt, it refers to when they damaged indirectly.
The Lechem Mishneh points out that the advantage of the Rambam's explanation is that he does not need to say that the wording of the Mishnah (32a) is imprecise. Two people who were walking in the public domain who damaged each other are exempt because they damaged each other indirectly.
In contrast, the Rambam understands that the statement of Rava (48b) -- that when they damage each other they are liable even when both have permission to be there -- refers to a case in which they damaged deliberately.
The disadvantage of the Rambam's explanation is that it seems inconsistent with the Gemara earlier (26b) which teaches that a person who damages is liable even when he does so accidentally. The Magid Mishneh (Hilchos Chovel 6:3) notes that the RA'AVAD indeed disagrees with the Rambam because he understands the Gemara in the way that Rashi does. (D. BLOOM)
2) THE OWNER'S LIABILITY WHEN HIS ANIMAL DAMAGES BY FALLING
QUESTIONS: The Mishnah (47b) states that when a person brings his ox into someone else's courtyard without permission and it falls into the water pit and causes the water to become putrid, the owner of the ox must pay for the damage to the water. Rava (48b) qualifies the Mishnah's ruling. The owner is liable only if the ox makes the water putrid at the moment that it falls (direct damage; see RASHI DH she'Hivish) but not if the damage occurs later, after the animal has fallen.
The Mishnah continues and says that if the father or son of the owner of the courtyard was in the pit and the ox fell on him and killed him, the owner of the ox must pay Kofer. The Mishnah adds that if he had permission to bring his ox into the courtyard, the owner of the courtyard is liable.
The Gemara (48b) asks why must the owner of the animal pay Kofer; the animal is a Tam, and a Tam does not pay Kofer! The Gemara gives three answers to this question. Rav answers that the ox indeed was a Mu'ad to fall on people in pits (it had done so three times). The Gemara concludes that according to this answer, the ox fell in the pit because it saw grass next to the pit and came to eat it, and it accidentally fell into the pit (see Rashi DH Chaza). In such a case, where the ox killed without intention to kill, the owner must pay Kofer but the ox does not have to be put to death. Shmuel answers that the Mishnah follows the opinion of Rebbi Yosi ha'Glili who maintains that a Tam must pay half the value of Kofer. Ula answers that according to Rebbi Yosi even a Tam pays full Kofer if it killed someone in its own yard, and the Mishnah follows this opinion.
According to Shmuel and Ula, even if the ox fell into the pit b'Ones (beyond its control) the owner still should be liable for the damage it did. (In contrast, according to Rav's answer, the fall was not b'Ones because the animal deliberately approached the edge of the pit to eat the grass, and it should have been careful not to fall in.)
This ruling appears to contradict other rulings in Bava Kama, which imply that the owner is exempt when his animal falls b'Ones. The Mishnah (55b) states that if an animal fell into a garden and benefited from what it ate there, the owner must pay for the benefit that his animal derived. Rashi (DH Naflah) explains that the animal fell b'Ones from the owner's roof into the adjacent garden of a neighbor. Rashi (DH Mah she'Nehenis) explains that the owner pays for the benefit his animal derived but not for the damage that it did. This is because an owner does not have to pay for damage that his animal did b'Ones. (This is in contrast to damage done by a person b'Ones, for which one is liable; see 26b.)
Similarly, the Mishnah (21b) states that one's dog or goat jumped off the roof and broke someone else's utensils, the owner must pay for the damages in full. The Gemara there infers that he is liable only because the animal jumped. If the animal fell, the owner is exempt, because the damage was done b'Ones. It is clear from there that damaged caused by a falling animal is considered an Ones for which the owner is exempt. Why, then, is the owner liable in the case of the Mishnah here, where the ox fell into the pit b'Ones?
ANSWER: The PNEI YEHOSHUA answers that the owner is liable in the case of the Mishnah here because he brought his ox into his friend's yard without permission. This is considered a case of "Techilaso b'Peshi'ah v'Sofo b'Ones," where the damage that occurred b'Ones was a result of the owner's initial negligence, for which one is liable. Since the owner brought the ox into his friend's yard without permission, he is obligated to pay even though the damage occurred only b'Ones, when the animal fell. In the two other cases (21b and 55b), no negligence on the part of the owner lead to the Ones. (D. BLOOM)