1) SELLING A SLAVE FOR THE RIGHT TO RECEIVE THE "KENAS"
QUESTION: The Gemara asks what the Halachah is in a case of an owner of an Eved who sells his rights to receive the "Kenas," so that if an ox ever gores the Eved, the Kenas due to be paid to the owner will go instead to the buyer of the rights to receive the Kenas. For all other purposes, however, the original owner is still the full owner of the Eved. Is the owner allowed to sell his Eved only with regard to receiving the Kenas?
The Gemara says that this question applies according to both Rebbi Meir and the Rabanan. Although Rebbi Meir generally rules that a person may buy or sell an item that has not yet come into existence (and thus, in this case, the owner should be able to sell the rights to the future Kenas), perhaps this case is different. In a normal case of a "Davar she'Lo Ba l'Olam," the item is certainly going to come into the world (such as fruits that will grow on a tree). In this case, however, it is possible that there will never be any Kenas because perhaps the Eved will not be gored by an ox, and even if he is gored by an ox perhaps the owner of the ox will admit to the crime and thus exempt himself from the Kenas ("Modeh b'Kenas Patur"). Accordingly, Rebbi Meir's opinion in such a case remains in doubt.
The question also applies according to the view of the Rabanan who rule that a person cannot buy or sell an item that has not yet come into existence. Perhaps the Kenas of an Eved is different because all of the factors involved in causing the Kenas presently exist (that is, the Eved and the ox). Hence, the Kinyan is considered as though it is being made on an item that is in existence.
The Gemara's explanation for why its question applies to the view of the Rabanan is difficult to understand. Most of the cases which the Gemara classifies as cases of "Davar she'Lo Ba l'Olam" also fit this description of the Kenas of an Eved. For example, when one buys "Peros Dekel," the fruits of a tree which have not yet grown on the tree, both the land and the tree are in the world; when one sells a field which he has not yet purchased ("Sadeh Zu l'k'she'Ekachenah"), the land, buyer, and owner are all in the world, but since the item being bought is not yet in the possession of the one who wants to sell it, the sale is considered to be taking place on a "Davar she'Lo Ba l'Olam."
ANSWER: The RASHBA explains that the case of the Gemara is a case of "Dekel l'Perosav." The Gemara states that if the transaction does not involve the sale of the fruits themselves for when they grow, but rather it involves the tree with regard to its fruit, it is considered a sale of a "Davar she'Ba l'Olam" since the tree is in the world and the owner is selling a certain "part" of the tree (its ability to create output). This is what the Gemara means: the sale was made on the actual body of the Eved with regard to his ability to produce a Kenas. (See also TOSFOS DH Eved.)
(The Rashba points out the difficulty in this explanation in light of the wording of the Gemara, but upholds this explanation because of the above questions.)
Based on the explanation of the Rashba, the difference between buying an Eved with regard to his Kenas and buying a tree with regard to its fruit may be understood. In the classic case of buying a tree for its fruit, the fruit grows directly out of the tree. Indeed, one easily can visualize a certain part of the tree from which the fruit will grow, and it is that part which is now being sold. In contrast, in the case of the Kenas of an Eved, the Kenas does not grow out of any part of the Eved. The Eved is just the cause for the obligation to pay the Kenas; there is no part of the Eved from which the Kenas comes out. The KETZOS HA'CHOSHEN (29:4) proves from the Gemara here that when one buys a tree for its fruit, the fruit does not need to be a direct outgrowth of the body of the item that exists now, but it can be any direct consequence that the body causes to come about. Such an "outgrowth" is considered a dimension of the body that exists now and is therefore considered a "Davar she'Ba l'Olam."