1) "BEREIRAH" CONTINGENT UPON WHAT SOMEONE ELSE DOES
OPINIONS: The Gemara suggests that even according to the opinion that maintains "Yesh Bereirah" (see Background), there is a difference between a case of Bereirah in which when one effects a change of status conditional on what someone else does ("Toleh b'Da'as Acherim"), and a case of Bereirah in which one effects a change of status conditional on what he does himself ("Toleh b'Da'as Atzmo"). What is the logic to distinguish between the two cases?
(a) RASHI (DH Amar Abaye) explains that when a person makes the change of status conditional on what he does himself, the fact that he makes such a condition demonstrates that he has not really made up his mind what he will do and that he intends to decide at a later point. At the moment he stipulates the condition, he has left his options open ("Pose'ach Al Shtei Se'ifim"). Therefore, when he later chooses to act one way or the other, his act cannot be said to reveal that he originally intended to make the change in status take effect in this manner (since originally he was clearly undecided). In contrast, when he makes it conditional on what another person will do, when the other person acts in one way or the other, his action determines what the person's original intention was.
Rashi's explanation here is consistent with the way he explains Bereirah in general. Rashi explains in many places (see Rashi here, 24b, DH l'Eizo; Chulin 14a, DH Osrin; Gitin 73b, DH u'Meshani) that "Ein Bereirah" means that the change which the person wants to effect does occur, but the way in which it transpires remains unclear. For example, when a person has two fruits of Tevel and says, "If it rains tomorrow, the one on the left will be Terumah for the one on the right, but if it does not rain tomorrow, the one on the right will be Terumah for the one on the left," according to Rashi one of the two fruits certainly becomes Terumah, but which one it is remains in doubt. According to the way most Rishonim understand "Ein Bereirah," neither fruit becomes Terumah because "Ein Bereirah" dictates that a present status cannot take effect based on a future event. According to Rashi, however, one of the fruits is Terumah, but exactly which fruit is Terumah remains in doubt. The change of status takes effect, but the details which depended on the future event remain in doubt even after the future event occurs. In this case, a Kohen is permitted to eat both pomegranates because one of them is Terumah and the other is Chulin, and neither one is Tevel.
Rashi understands that when one makes a Kinyan dependent on a future event, the Kinyan does not depend on what actually happens in the future (since the Kinyan must take place now). Rather, it depends on what is destined -- at this point in time -- to happen in the future. Even if it actually does rain tomorrow (in the example above), those who rule "Ein Bereirah" maintain that the Kinyan does not take effect because it was impossible to know on the previous day, when the condition was stipulated, that it was destined to rain the next day. (TOSFOS Eruvin 37b, DH Ela, cites a similar ruling in the name of MAHARI. See CHIDUSHEI REBBI AKIVA EIGER in Ma'arachah #4 to Eruvin 38a, DH v'Nir'eh d'Vein. See also Insights to Eruvin 37:1, Yevamos 67:1, Gitin 73:2, Zevachim 3:1, and Chulin 14:3.)
The opinion that rules "Yesh Bereirah" maintains that an act which occurs in the future can determine -- at the time the condition was stipulated -- what was destined to happen in the future. However, the Gemara here suggests that if a person makes the present change of status contingent upon his own future actions, what he eventually decides to do cannot determine what his original intention was since he demonstrated at the time of the condition that his intention was still undetermined.
The TOSFOS HA'ROSH (here and in Eruvin 36b) asks a strong question on Rashi's explanation. The Gemara cites as an example of "Toleh b'Da'as Atzmo" the case of a person who buys a barrel of wine from Kusim. The buyer has no containers available with which to separate Terumah and Ma'aser from the wine, and yet he needs to drink from the wine right away. Rebbi Meir rules that he may declare that the wine which he will separate later when he finds containers should be Terumah now. He does not separate the Terumah and Ma'aser now because he does not want the Terumah and Ma'aser to become mixed with the rest of the wine in the barrel which he wants to drink, and not because he wants to "leave his options open." Why, then, should this case of Bereirah be less effective than Bereirah which is contingent upon someone else's future actions ("Toleh b'Da'as Acherim")? The RASHASH, TIFERES YAKOV, and others suggest tenuous answers to this question.
(RABEINU KRESKAS phrases the difference between "Toleh b'Da'as Atzmo" and "Toleh b'Da'as Acherim" somewhat differently from Rashi. His words imply that even if nothing in the person's statement shows that he is "leaving his options open," nevertheless Bereirah should not apply in a case of "Toleh b'Da'as Atzmo." His reasoning is that we assume that something was predetermined to happen in a particular way only when it happens by itself, independent of the actions of man. If an event which occurs in the future evolves through the actions of man, since man has free choice the outcome of his actions are never "predetermined." In effect, the Gemara is distinguishing between a future event which does not depend upon human intervention and one which does depend upon human intervention. Although this explanation answers the Tosfos ha'Rosh's question from the case of Bereirah with regard to separating Terumah (since the person's future act of separating Terumah certainly involves human intervention), it does not seem to explain why Kidushin performed "Al Menas she'Yirtzeh Aba" is in the category of "Toleh b'Da'as Acherim," since that case obviously involves human intervention. This question may be the reason why Rashi phrases the difference between "Toleh b'Da'as Atzmo" and "Toleh b'Da'as Acherim" the way he does. The Tosfos ha'Rosh's question on Rashi's explanation, however. remains to be answered.)
Perhaps Rashi means that since, normally, when one is "Toleh b'Da'as Atzmo" it means that the person is still undecided, therefore the Rabanan instituted that we say "Ein Bereirah" (l'Chumra) in any case of "Toleh b'Da'as Atzmo," even in a case such as that of a person who purchases a barrel of wine and does not have containers with which to separate Terumah and Ma'aser, where the person does not show that he is undecided about what he wants to separate as Terumah and Ma'aser. (This conforms to the implication of the wording at the end of the Beraisa which discusses separating Terumah -- cited at the top of 26a -- "do you not admit to us that there should be a Gezeirah to invalidate the Terumah in this case...." This wording implies that those who argue with Rebbi Meir and rule that the Terumah is not valid maintain that Bereirah does not apply mid'Rabanan.)
(b) Most Rishonim explain that "Ein Bereirah" means that one cannot effect a Kinyan, or a change of status, now based on the outcome of an event in the future. A Kinyan must take effect completely at the time that the Ma'aseh Kinyan is performed. If one attempts to make a change of status dependent upon a future event, it will not take effect at all (see RAN, Nedarim 45b). This is in contrast to the view of Rashi (as mentioned above) who maintains that the change does take effect but it is unknown in which way it takes effect. According to the view that maintains "Yesh Bereirah," a person can effect a change of status now which depends upon a future event, and that future event will determine retroactively whether or not the change of status took place.
According to these Rishonim, there seems to be no logical reason to distinguish between "Toleh b'Da'as Atzmo" and "Toleh b'Da'as Acherim" in the way that Rashi suggests, since these Rishonim maintain that when a person makes his present action dependent upon a future event, he makes it dependent upon what actually will occur in the future, and not upon what is destined -- at the present moment -- to occur in the future.
The difference between "Toleh b'Da'as Atzmo" and "Toleh b'Da'as Acherim" would seem to be that Bereirah operates only when it is necessary, such as when a person makes a change of status dependent upon a different person's future act. However, when a person makes a change of status dependent upon his own future act, Bereirah does not work, since it is in his power to decide now what he will do later, and it is in his power to make the change take effect now and not be contingent upon a future act. (This understanding, however. does not seem to resolve the question which the Tosfos ha'Rosh poses on Rashi's explanation.)
A possible difference between the approach of Rashi and the approach of the other Rishonim with regard to "Toleh b'Da'as Atzmo" may exist in a case in which a person stipulates that a change of status is contingent upon what a person who is present decides to do at a later time. According to Rashi, this is comparable to "Toleh b'Da'as Atzmo," since the person upon whom the change of status is contingent obviously is undecided and wants to decide at a future time what to do. According to the other Rishonim, since the one who is making the condition cannot decide what the other person will do, it should be considered a case of "Toleh b'Da'as Acherim."

25b----------------------------------------25b

2) THE DIFFERENCE BETWEEN "BEREIRAH" AND A "TENAI"
QUESTION: The Gemara teaches that when one makes a Kinyan or change of status dependent upon a future event, it is called "Bereirah" and, according to some Tana'im, the Kinyan does not take effect because "Ein Bereirah." The Gemara in Eruvin (36b) gives an example of a case of Bereirah: a person makes an Eruv Techumin with a stipulation that if a certain Chacham comes to one side of the town, his Eruv Techumin should take effect on that side, and if the Chacham comes to the other side, his Eruv should take effect on that side.
Why does the Gemara consider this a case of Bereirah? Perhaps when one stipulates, "If the Chacham comes to the east, my Eruv is to the east," the Eruv is valid because it involves no more than a normal case of a "Tenai" (a "yes" or "no" condition). It is comparable to a case in which a man says to his wife, "If you do this act, this Get will be valid, and if you do not do this act, the Get will not be valid."
The same question applies to the Gemara's case of a man who betroths a woman conditionally and makes the Kidushin dependent on the woman's father consenting to the marriage. This case also seems to be no more than an ordinary condition in the Kidushin. Why is it a case of Bereirah?
ANSWERS:
(a) RASHI (DH ul'Chi Mayis) writes that a condition, a Tenai, works only because the ability to fulfill the condition is in the hands of one of the parties involved, and it was the person's intention that the condition be fulfilled at the time that he stipulated the Tenai. (That is, because he plans to fulfill it and he wants the transaction to be consummated, the event that is contingent upon the completion of the Tenai takes effect immediately, even before the Tenai is executed. If the Tenai ends up un-fulfilled, then the event is uprooted retroactively. It is not possible to cause an event to take effect retroactively.)
This is not how the condition works in the case of Eruv Techumin (in Eruvin) or in the case of one who betroths a woman on condition that her father consents. The fulfillment of the condition (that the Chacham comes to one side, or that the father consents) is not in the hands of the person who makes the statement. Since the Eruv, or the Kidushin, depends on an act that is not in the person's hands to fulfill, it is considered a case of Bereirah.
(b) The RAMBAN here disagrees with Rashi. He explains that a case of a Tenai exists when there are only two possibilities: either the event will occur or it will not occur. In contrast, when an event can occur in one of several ways it is not a case of Tenai. Rather, it is a question of Bereirah. The case of the Eruv that is dependent on the Chacham's arrival can occur in one of two ways (he could arrive in the east or in the west). Therefore, it involves Bereirah.
(b) The RAMBAN here disagrees with Rashi and explains that a Tenai is when there are two possibilities -- either the event will occur or it will not occur. On the other hand, when trying to make something happen which can occur in one of several ways, it is not a case of Tenai but a question of Bereirah. The case of the Eruv dependent on the Chacham coming to one of two sides is such a case. The event -- the Eruv taking effect -- will happen in one of two places, and it is the arrival of the Chacham which will determine where the Eruv will take effect. The Ramban writes that the case of Kidushin is an exception; although there is only one Kinyan involved (the Kidushin of the woman), since it is dependent not on an action but on a person's decision (the father's consent), it is considered a case of Bereirah. (See also RABEINU KRESKAS)
One still may ask, however, why is the case of the Chacham a case of Bereirah? Perhaps the person's stipulation involves two completely separate conditions. The first condition is that if the Chacham comes to the east, then the Eruv will be to the east, and if he does not come to the east, then the Eruv will not be to the east. The second condition is that if the Chacham comes to the west, then the Eruv will be to the west, and if he does not come to the west, then the Eruv will not be to the west. (See REBBI AKIVA EIGER, Ma'arachah #4 to Eruvin 38a. TOSFOS (end of Yoma 56a) in fact asks this question on the explanation of the Ramban.)
Apparently, the Ramban maintains that the establishment of the two Eruvei Techumin cannot be viewed as two independent events. Rather, one event takes place (an Eruv is made), and there are two possibilities as to how it will take place (to the east or to the west). The reason for this is that one cannot make two Eruvim to be Koneh Shevisah in two places (since a person lives in only one place at a time). Therefore, when the person adds that if the Chacham comes to the other side then his Eruv will be to that side, it is viewed as an addendum to his first condition. (See also Insights to Eruvin 36:2 and Yoma 56:1.)