The Reliability of One Eid in Situations of Be-Yado
Unlike monetary situations, issur-based halakhic uncertainties may be determined or decided on the basis of one witness, an eid echad. The testimony of one witness regarding the status of meat or any other halakhic question is accepted. However, the gemara limits this capacity to situations of halakhic vacuums (see, for example, Gittin 2b). If there is NO prior knowledge, or chazaka one witness is believed. (Of course, if he SUPPORTS our prior knowledge by confirming a status or chazaka, he is also believed.) However, one witness is not believed to contradict a previously held status or a chazaka. For example, one witness would not be believed to testify that tevel produce had been remedied through the designation of the requisite teruma and ma'aser. Since his testimony alters a previously held chazaka that the crops are tevel, his solitary statement is insufficient.
However, the gemara introduces one scenario in which a lone eid CAN reverse previously held assumptions based on chazaka. If the state to which he testifies is "be-yado," -within his ability to personally induce- he is BELIEVED to claim that the state exists, even if he admits he did not personally generate it. For example, if he testifies that tevel produce under his guardianship has been resolved through teruma designation, he is believed. Even though he is altering the previous status of tevel, since he possesses the ABILITY to actually resolve tevel through personal intervention, he is believed in his claim that the tevel has been otherwise resolved. The principle of "be-yado" is invoked throughout Shas, but most directly in the gemara in Gittin (54b, 2b) and Yevamot (88a).
Presumably, the be-yado solution is based on AUGEMENTING the strength of the eid echad's statement. Typically, his statement is believed in a vacuum – "eid echad ne'eman be-issurin" – but when opposing a prior condition of chazaka, his unsupported statement is not RELIABLE enough to overcome our working assumption of chazaka. However, if the eid possess the ability to personally induce the state to which he testifies, his statement is overwhelmingly reliable. According to this perspective, "be-yado" is cast as a form of migu. Since he possesses the ability to induce the state, he has little reason to lie; if he truly wanted to create a resolved tevel state, he could easily have separated the teruma himself. The knowledge that he is not a liar provides the legal confidence to accept his statement even when opposed by chazaka.
To be sure, and as many note (see, for example, the Rosh, Gittin 54b), this may not be a classic "migu," since the eid often testifies about an event that, if performed by the eid, may have entailed financial liability. For example, an eid is believed to testify that teruma has become tamei if he possesses the ability to personally confer this impurity. However, had he conferred the impurity himself, he would have been liable to pay. Hence, he possesses incentive to lie and claim that OTHERS have caused the impurity; he isn’t automatically believed based on his NOT claiming that he personally impurified the produce. If be-yado were a type of migu, the eid should not be trusted in this case.
However, even though classic migu may not be operative, be-yado may be a derivative or parallel to migu that would apply even in this case. Be-yado may operate in a manner similar to migu in conferring augmented reliability to the eid.
The Maharik (15th century French/Italian author of responsa) introduced an entirely different view, arguing that the ability to create a change in the status of an item does not arm the eid with greater reliability. In fact, an eid CANNOT have his reliability reinforced, since an eid is an all or nothing proposition; either he is entirely believed inherently or he fails as an eid (see shiur #04migu.htm). Hence, if his testimony fails to overturn a chazaka, his testimony “strengthened by be-yado” would not be MORE successful in overturning a chazaka. Instead, the Maharik argues, the state of be-yado WEAKENS the opposing chazaka. A chazaka is based upon assuming “stasis:” if the halakhic state existed, we must assume it continues to exist until proven otherwise. If an individual has the ability to unilaterally alter the state, the chazaka is either non-existent or significantly weakened into an inferior chazaka against which a lone eid is believed.
This question regarding how be-yado works may have inspired a fundamental machloket about the DURATION of the be-yado concept. The gemara in Gittin (54b) cites Abaye, who limits be-yado to a scenario in which the person STILL enjoys the be-yado capacity when he testifies. If the ability has already concluded, even though he ONCE POSSESSED that ability, the lone eid is no longer believed to overturn a chazaka. Rava disagrees, arguing that if a lone eid ONCE possessed capacity to induce a status, he is always believed to testify toward that status.
Perhaps Abaye's limitation of the rule is rooted in viewing the be-yado concept as based upon “strengthened reliability.” If the person CURRENTLY has the ability to install a status, he has little incentive to lie about that status, and he is therefore believed. If he ONCE possessed that ability but no longer does, he MAY possess incentive to testify falsely, and he is therefore no longer believed. Rava may have countered that be-yado does not confer augmented reliability to the eid, but rather weakens or disables the chazaka. If the item in question was "vulnerable" to change and could easily have been altered, its reigning status is not “sealed” and the chazaka does not bar the testimony of the eid. Thus, Abaye and Rava may have been debating whether be-yado ADDS to the reliability of the eid or merely weakens the chazaka. The expression of this debate impacts the duration of the be-yado ability.
Interestingly, Rava introduces a different limitation to the be-yado concept. If the eid did not supply the testimony when first asked but subsequently offered his testimony, he is not believed, even though he possesses the be-yado capacity to alter the item. Apparently, his initial silence raises suspicion, thereby disqualifying his subsequent statements. If be-yado – the capacity to have personally affected the testified status – confers augmented reliability upon the eid, the suspicions aroused by initial silence should not affect his ability to testify. Just as the be-yado ability confers strengthened reliability to overturn a chazaka, it should assuage suspicions raised by his initial silence. Perhaps Rava consistently viewed the be-yado principle in the same manner as the Maharik – it weakens the chazaka and allows one eid to testify as if there were no chazaka. However, if the conduct of the eid has aroused suspicion, his position is suspect and his testimony unacceptable. Be-yado does not provide an overarching augmented reliability that allays fears of false testimony. Furthermore by viewing be-yado as a chazaka diminisher, Rava stretched the application even in instances in which the ability has expired.
An additional question that may be influenced by the nature of be-yado is the scope of be-yado. Would it enable an eid echad to testify regarding areas that typically require two eidim? As stated above, the allowance for one eid was stated primarily in areas of issur. Areas concerning erva, such as marriage and divorce, require two eidim – "ein davar she-bi-erva pachot mi-shnayim." Would one lone eid be believed to testify about an erva situation if it were a be-yado situation?
The gemara in Gittin (2b) raises this as a possibility, but subsequently rejects it. However, the gemara in Kiddushin (64a) implies that it might work. The gemara cites a machloket regarding a dying person who testifies that he has children, thereby exempting his wife from yibum by his living brothers. Abaye claims that at least according to Rebbi, the dying person is believed; since he has the ABILITY, or be-yado, to exempt her from yibum by currently delivering a get, he is believed to exempt her from yibum even though he is testifying about an erva condition. This is consistent with Abaye's aforementioned view in Gittin (54) that be-yado confers augmented reliability. The augmentation would only last as long as the option still remains, but it MAY augment the eid sufficiently so that he can impact erva situations. Presumably, if be-yado merely weakens the chazaka but does not augment the status of the eid, it would not enable one eid to testify about erva situations, but it would be operative even after the be-yado ability terminated.
An interesting comment of Tosafot in Kiddushin establishes an association that may reflect the Maharik's view of be-yado. The gemara (54a) claims that a father is believed to testify that his child has reached the age of mitzvot. One way of understanding this gemara is to attribute this ability to the special status enjoyed by a father to testify about his child. Explained in this manner, the gemara yields little information about the nature of general eid echad and the allowance of be-yado. Tosafot, however, wonder why the lone eid is believed even against a chazaka. Evidently, they understood this instance as a CLASSIC situation of eid echad and were therefore troubled by the capacity to overturn chazaka even though the father does not have the be-yado ability to advance his child's age. Tosafot claim that since a child NATURALLY AGES, it is CONSIDERED a case of be-yado in which one eid –in this case the father- is believed even against a chazaka. Even though the father cannot personally affect the aging process, the very fact that the process is dynamic and irreversible renders this situation comparable to be-yado, in which a lone eid (and presumably everyone, not just a father) would be believed.
If the ability of be-yado confers augmented reliability, this association is not logical. The father has no ability to personally advance his child's age and therefore should enjoy no augmented reliability. If the Maharik is correct, however, and the ability to change a status weakens the assumed stasis of chazaka, Tosfaot's extrapolation is logical. If ABILITY to affect change ruins stasis, certainly NATURALLY OCCURRING CHANGE should weaken the chazaka. Once the chazaka is weakened, a state similar to be-yado has emerged and a lone eid is believed.
A final issue which may reflect the nature of be-yado concerns the SOURCE of the be-yado phenomenon. Rashi in Gittin (2b) implies that the be-yado idea does not require a source, but is instead a logical principle. Since the Torah believes people about day-to-day activities (such as food preparation), evidently, this reliability extends to situations of be-yado and grants reliability even to overturn a chazaka. Tosafot cite the example of a nidda who is believed to testify that she immersed in a mikve because she has the ability to CURRENTLY immerse in a mikve. This reliability serves as the paradigm for all situations in which an eid is believed to overturn a chazaka because of the be-yado condition.
Perhaps this debate about the need for a source for be-yado reflects the different manners of understanding this principle. If be-yado augments the eid's reliability to overturn chazaka, it is effectively extending his status beyond NATURAL scales. This extension would likely require an explicit source. Of course, the structural similarity to migu must then be analyzed, and we may question why the source for migu is insufficient.
Alternatively, the be-yado dynamic (as stipulated by the Maharik) merely weakens the chazaka, thereby rendering the context as one in which no prior status exists, and the eid is believed just as he is “naturally” in a situation in which there is a vacuum. This “neutralizing” ability of be-yado would not require a pasuk and could be intuited naturally, as Rashi's comments suggest.