QUESTION: The Gemara asks why Rebbi Yosi is lenient in a case of a doubt that involves Eruv Techumin (which is d'Rabanan), while he is stringent in a case of a doubt that involves Tum'ah d'Rabanan. The Gemara answers that Eruv Techumin is an enactment of the Rabanan that is not based on any law mid'Oraisa, while the enactments of Tum'ah d'Rabanan are based on the laws of Tum'ah mid'Oraisa.

The Rishonim point out that only the Techum of 2000 Amos is mid'Rabanan. The prohibition to walk more than 12 Mil (12 X 2000 Amos) on Shabbos, however, is forbidden mid'Oraisa (as is derived from the size of the encampment of the Jewish people in the wilderness; see RIF, end of first chapter of Eruvin, and RAMBAM, Hilchos Shabbos 27:1, based on the Yerushalmi). Since there is a concept of a Techum d'Oraisa, the enactment of Eruv Techumin has a source in the Torah. Why, then, does the Gemara say that it has no source in the Torah? (RASHBA, RITVA)

(a) The RASHBA and MAHARAL (Gur Aryeh, end of the first chapter of Eruvin) answer that even though there is a Techum d'Oraisa, the enactment of Eruv Techumin has no source in the Torah. The Torah does not permit one to walk beyond the 12 Mil, nor does the enactment of Eruv Techumin enable people to walk beyond the Techum d'Oraisa.

(b) RAV GEDALYAH RABINOWITZ zt"l (of Manchester) in GIDULEI HEKDESH points out that the answer of the Rashba and Maharal seems to be subject to dispute. The RAMBAN (Eruvin 17b) writes that if the laws of Techumin are mid'Oraisa, then Eruv Techumin must also be d'Oraisa (either as a Halachah l'Moshe mi'Sinai or through logic ("Sevara")). The Ramban adds that according to the opinion that the Techum of 12 Mil is mid'Oraisa, there is also a Halachah l'Moshe mi'Sinai (or Sevara) that if one makes an Eruv for such a Techum, it permits him to walk another 12 Mil. Therefore, the concept of Eruv Techumin does exist mid'Oraisa.

Perhaps for this reason, the RA'AVAD (cited by the Rashba and Ritva) explains that the Gemara does not mean that there is no Techum mid'Oraisa. Rather, the Gemara means that the reason the Rabanan prohibited one to walk 2000 Amos is entirely unrelated to the Torah law of the 12-Mil Techum (because if their enactment was related to the Isur d'Oraisa of Techumin, then why did they choose to prohibit such a small fraction of the Torah's Techum?). In fact, the Rabanan inferred from the laws of the cities of the Levites (Eruvin 51a) that the boundaries of a city extend 2000 Amos beyond its walls. Therefore, they enacted that one may walk up to 2000 Amos from his place of Shevisah on Shabbos and Yom Tov.

(c) The RITVA writes that the Gemara means only that Rebbi Yosi maintains that there is no law of Techumin d'Oraisa at all. Other Tana'im, however, maintain that mid'Oraisa there is a Techum of 12 Mil.

QUESTION: The Gemara quotes the ruling of Ayo, who says that one may make an Eruv Techumin with a stipulation only with regard to one side of town or the other. He may stipulate that whichever side of town is visited by the Chacham is the side on which the Eruv should take effect. He may not say that if two Chachamim come (one on each side of town), then he reserves the right to choose, on Shabbos, the side on which his Eruv will take effect.

The Gemara points out that, in both cases, the person utilizes Bereirah. Why, then, is the stipulation in the second case not valid while the stipulation in the first case is valid? The Gemara answers that in the first case, the Chacham has already arrived in one of the towns, and therefore the location of the Eruv will not be determined by a future event. Rather, it is determined by the present location of the Chacham (which will only be known when word of his arrival reaches this town).

Why does the Gemara not suggest a very simple difference between the two cases of Ayo? Perhaps even when one stipulates, "If the Chacham comes from 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 where a divorcing husband says to his wife, "If you perform this act, this Get will be valid, and if you do not perform this act, the Get will not be valid." In contrast, when the person says, "If two Chachamim come, I will choose tomorrow where I want my Eruv to take effect retroactively," there is no condition. The issue in that case is one of Bereirah, and thus the Eruv is not valid. Why does the Gemara consider the first case to be a case of Bereirah and not a normal case of a Tenai?

(a) RASHI in Gitin (25b, 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 remains unfulfilled, then the event is nullified 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. The fulfillment of the condition (that the Chacham comes from one side) is not in the hands of the person who made the statement. Rather, it depends on the Chacham, who has nothing to do with the Eruv. Since the Eruv depends on an act that is not in the person's hands to fulfill, it is considered a case of Bereirah.

(b) The RAMBAN in Gitin (25b) argues with Rashi. He explains that a case of a Tenai is 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.

One may still 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 only in 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.