TB Sanhedrin 5a brings that one expert can be a judge in monetary cases and that he is equivalent to a normal court of 3.  The Talmud then questions whether the expert also needs to be authorized by the rabbinical establishment for his decisions to be considered final. (The gemara assumes that de facto anyone can deliver a judgement, but if he was not allowed to, de jure, then if he errs, the decision can be cancelled.)  It is proven that his decisions are final even where he has not be granted authority, assuming he is an expert, from the case where a expert who erred was told to personally pay the defendant back his money.  Since the decision was not simply cancelled and the plaintiff not made to return the money, we learn that an expert’s decisions are in fact final, even where he has no official authority.  Were he to have authority, he would also not be required to personally pay the defendant.

Tosfot  (ד”ה מומחה) compare our sugia to a passage on page 23a which starts off by rebuffing Rabbi Meir, and telling him that a litigant cannot reject a judge that is an expert, implying that Rabbi Meir believes you can reject such an expert judge. The Gemara then corrects the statement to be merely telling Rabbi Meir that you cannot reject a judge who was given the status of expert without being an expert.  Rabbi Meir then only differs in holding that such a non-expert expert can be rejected, but all agree that a true expert cannot be rejected.   Tosfot point out that the sugia there (23a) does not mean to imply you must have experts on every court.  This seems obvious to me.  Then Tosfot say that in fact, even average people, once they are composing a court of 3, will, for the purposes of that court, be considered experts, even without being extremely learned. We might object to Tosfot, if every court is considered to be composed of experts, as Tosfot say, then how can the gemara on 23a state that expert judges cannot be rejected? They are all always experts!  Rather, when they are still being appointed to the court, they are not yet experts and so can be rejected, but not after they are sitting. Tosfot are bolstering the court and denying the possibility of invalidating judges once they have been composed into a sitting court, Aside from reconciling the sugia on 23a, we can say that tosfot have broaden the definition of expert so that all courts will have the same validity and cannot be invalidated after the fact.

Tosfot (ד”ה דן אפילו יחידי) demonstrate that the discussion of what or who makes a court is really a question of making a court that can force people to appear before it (and presumably, force them to comply with its decisions). For if the litigants all consent to be judged by a man, even an average man, then his decision is binding on them (assuming the judge pronounces a correct judgement). Tosfot therefore conclude that a single expert or a court of 3 average people can force litigants to court. Interestingly, the court of 3 average people is compare to a single expert, not the reverse, thereby implying that a single expert as judge is the primary law (an interesting inversion). Shmuel’s case of a court of 2 (non experts) that are called “presumptuous” can likewise force litigants.  And the case of זבל”א on 23a is where 2 judges exist and the third one is voluntarily chosen by (in one opinion) the litigants. If the litigant can choose judges, doesn’t that mean the litigant must be there voluntarily? Couldn’t he choose not to be there just the same? To this Tosfot answer that he can choose only who will judge him, but he cannot choose to no come to any court.

Pirke Avot advises not to judge alone because you might err.  So how could Rav Nachman and Rav Hiya say they judge alone?  Tosfot (כגון אנא) answer, they are only saying they are capable of judging, but don’t actually judge alone.  Alternatively, they do judge alone, but because they are constantly involved in judgments, they won’t err.  This gives us a new category, a well practiced expert.

Rashi holds that an expert דלא נקיט רשותא who errs must pay if the litigants asked him to judge them “according to the Torah law” if they didn’t accept upon themselves possible errors in judgment. Tosfot (ואי לא) argue from the gemara דן את הדין on 6a that this law would apply even to one who is not an expert (even according to rashi there). Tosfot say that the teaching here is that since this is a case of an expert judge, even where the litigants did not agree to the judge at all, if he errs, the judge must pay the defendant and his judgement cannot be reversed.  Were the judge also to have נקיט רשותא it would have saved him from having to pay. Rashi was only able to explain the necessity for the judge to repay by the litigants’ request for the judge to apply correct Torah law which the judge failed to do. If they had not accepted the judge at all, where an error has occurred, the judgment would be nullified. Tosfot instead have granted even a non-authorized expert the ability to force the litigants to court and therefore they do not need this to be a case of acceptance (based on Tosfot ד”ה דן אפילו יחידי ). What prevents Rashi from accepting tosfot’s explanation? Does Rashi hold that an expert can force, but only if he produces the correct judgment?  Otherwise an expert’s forcing does not count? It is a strange mix for rashi to agree to the forcing (assuming he does) yet invalidate the din when the judge erred. But we find a precedent for this kind of rule in the law that a man can execute his own judgment if he knows he is right (עביד איניש דינא לנפשיה) BT BK 27b

יש לאדם לעשות דין לעצמו אם יש בידו כח, הואיל וכדת וכהלכה הוא עושה – אינו חייב לטרוח ולבוא לבית דין, אף על פי שלא היה שם הפסד בנכסיו אילו נתאחר ובא לבית דין, לפיכך אם קבל עליו בעל דינו והביאו לבית דין ודרשו ומצאו שעשה כהלכה ודין אמת דן לעצמו – אין סותרין את דינו

(משנה תורה, הלכות סנהדרין, פרק ב’, י”ב)

Tosfot ask if Bavel rabbinic authorization is valid in Israel, but not the reverse, implying Bavel is more authoritative, doesn’t that contradict Pesachim 51a that Bavel is said to be subsidiary to Israel regarding customs?  See also 24a here. Tosfot answer that although the Rabbis of Israel are more learned and they are to be followed in some matters, regarding money matters, Bavel has more authority, because Bavel’s authority derives from the sons of David, not the daughters.  Other Rishonim say the authority is from the the secular powers that grant more power in Bavel.  The gemara in Pesachim is convoluted, for it allows Bavel to have a different custom from Israel because Bavel is subsidiary to Israel.  But if that is the case, then Bavel should change to be in accord with Israel.  Why doesn’t it. Apparently they are independent of each other.

Tosfot (נקיטנא) explain that there are two systems of authority: regular authorization from the leaders of Bavel or E. Israel and personal smicha from a rabbi who himself has received smicha. Tosfot then propose that possibly where there is a chief rabbi of a city, only he is allowed to give smicha.