In a case where someone says 'Ish P'lonii Yirshani' when he has a daughter, or 'Biti Tirshani' when he has a son, our Mishnah rules 'Lo Amar K'lum' on the basis of the principle - 'Kol ha'Masneh al Mah she'Kasuv ba'Torah, Tena'o Bateil'.

According to Rebbi Yochanan ben Berokah, if he says it with regard to a potential heir, his words take effect.

We can extrapolate from the words of the Tana Kama that - if he would bequeath his property to 'Ben bein ha'Banim', his words would take effect.

The problem with this is that it seems to tally with the opinion of Rebbi Yochanan ben Berokah in the Seifa (so what are they arguing about)?

In an attempt to answer the Kashya, we establish Rebbi Yochanan ben Berokah - by a brother where there is a daughter (but no son) and a daughter, where there is a son.

We refute this suggestion however, on the basis of a Beraisa. Rebbi Yishmael, Rebbi Yochanan ben Berokah's son there defines the Machlokes between his father and the Chachamim - by Ben bein ha'Banim and Bas bein ha'Banos ...

... but in the case of Acher be'Makom Bas' and 'Bas be'Makom Ben' - his father will concede.

Based on the wording of Rebbi Yishmael B'no shel Rebbi Yochanan ben Berokah's statement - we extrapolate that, according to the Tana Kama, they do indeed argue over Acher be'Makom Bas' and 'Bas be'Makom Ben'.

Alternatively, the entire Mishnah goes according to Rebbi Yishmael ... , and we merely need to add a few words which establishes the Machlokes by Acher be'Makom Bas' and 'Bas be'Makom Ben.

We could explain that in the previous Mishnah, the Tana presents the case of Ben bein ha'Banim, and in this Mishnah, that of Bas be'Makom ha'Ben ... , in keeping with the principle 'Zu ve'Ein Tzarich Lomar Zu'. Alternatively (and preferably) we can explain that - in the previous Mishnah, the Tana taught us the extent of the Tana Kama (that even Ben bein ha'Banim does not acquire), and in this Mishnah, that of Rebbi Yochanan ben Berokah (that even Bas be'Makom Ben does).

According to the current explanation, in a case where someone bequeaths his property to his uncle, there where he has a daughter and a brother - Rebbi Yochanan will concede to the Chachamim that his words are invalid (since they are only valid there where he bequeaths to the one who directly follows the next of kin.

Rav Yehudah Amar Shmuel rules like Rebbi Yochanan ben Berokah - Rava agrees.

This ruling is confined to Ben bein ha'Banim, and does not extend to Bas be'Makom Ben (as is evident from our final version of the Mishnah a little earlier) as well as from Shmuel himself, who ought otherwise to have given an indication to that effect, and from Abaye earlier, who explicitly equates the Din of Rebbi Yochanan ben Berokah with 'Ben bein ha'Banim'.

It makes no difference whether he bequeaths to one of his sons - half his property ...

... or all of it ...

... orally or in writing; either way, his words are valid.

We reconcile this ruling with Shmuel, who will rule later, that if someone writes all his property to his wife or to one of his sons, he merely appoints them an Apotropos - by establishing the latter where the father (or husband) gave the property as a Matanah (since the position of Apotropos is also a gift), whereas Shmuel is speaking here where he bequeathed it as a Yerushah, which cannot b construed as an appointment as an Apotropos.

Rava learns from the Pasuk "ve'Hayah be'Yom Hanchilo es Banav" that - a father may bequeath his poperty to any one of his sons (of the next of kin, whoever they may be), like Rebbi Yochanan ben Berokah.

Abaye queries this however, because he learns it from the Pasuk "Lo Yuchal Le'vaker" - which implies that a father cannot deprive the B'chor of his Cheilek B'chorah, but a Pashut of his Chelek Pashut, he can.

Rava answers by quoting a Beraisa, where Aba Chanan Mishum Rebbi Eliezer learns from "Lo Yuchal Le'vaker" that - a father cannot deprive the B'chor of his Cheilek B'chorah.

We might have thought otherwise - because we would have learned from a Pashut (in which connection we Darshen "va'Hayah be'Yom Hanchilo es Banav", as we just explained) from a 'Kal va'Chomer (if a father can deprive a Pashut of his Cheilek Pashut, 'Kal va'Chomer' a B'chor of his Cheilek Bechorah) ...

The 'Kal va'Chomer' of B'chor from Pashut is - based on the advantage of a Pashut over the B'chor, inasmuch as a Pashut inherits from his father even what is Ra'uy, whereas a B'chor does not (as we have learned above).

We have now refuted Abaye's Kashya on Rava - because we see from the Beraisa that "Lo Yuchal Le'vaker" is needed for itself, to preclude a B'chor from the 'Kal va'Chomer', in which case, we cannot Darshen anything else from it.

Now that the Torah has written "Lo Yuchal Le'vaker" the Beraisa asks, why does it need to add "ve'Hayah be'Yom Hanchilo es Banav"? - why can we not simply extrapolate that if a father is not permitted to deprive a B'chor of his Cheilek Bechorah, that he is permitted to deprive him or any of his other sons of their Cheilek Pashut?

The Tana answers that - if not for "ve'Hayah be'Yom Hanchilo es Banav", we would rather have learned a 'Kal va'Chomer' from B'chor (who does not inherit Ra'uy) on to Pashut (who does), as we just explained, than preclude it from an inference.

Rebbi Zerika ... Amar Rebbi ruled like Rebbi Yochanan ben Berokah. When Rebbi Aba commented on this 'Horeh Itmar', he meant that - Rebbi did not just rule like Rebbi Yochanan ben Berokah theoretically, but that he actually issued a ruling accordingly in a case that was brought to him.

The basis of their Machlokes is - which of the two is stronger, 'Halachah' (because by Horeh, one can never be sure that one understands the circumstances of the Rebbe's ruling), or 'Horeh' (because based on the principle 'Ma'aseh Rav', one never knows for sure that a theoretical ruling is not confined to one's learning, but that if a practical case occurred, the Rebbe might rule differently).

The Beraisa says 'Ein Lemeidin Halachah Lo mi'Pi Limud ve'Lo mi'Pi Ma'aseh', incorporating the two alternatives that we just discussed. One can only rely - on a ruling where the Rebbe specifically states that his ruling is 'le'Ma'aseh' (to act upon).

The Beraisa actually states two cases 'Ad she'Yomru Lo Halachah le'Ma'aseh; Sha'al ve'Amru Lo Halachah le'Ma'aseh, Yeilech ve'Ya'aseh Ma'aseh'. The difference between them is that - whereas in the former case, the Rebbe needs to specifically authorize the Talmid to act on his ruling, in the latter case this is not necessary, because it is obvious.

In a Mishnah or Beraisa (which we have basically been discussing until now) - 'Halachah' is not the last word, and therefore requires the Gemara's backing before it can be accepted; whereas 'Halachah' in the Gemara is final.

The reason for this distinction is - due to the fact that firstly a ruling in the former is often subject to further Machlokes, whereas the rulings of Rav Ashi in the Gemara are meant to be the last word for all times.

When Rebbi Asi asked Rebbi Yochanan whether they could learn from his theoretical rulings, he replied that - they should not do so until he told them that it was Halachah le'Ma'aseh.

This would fall away after his death - because the reason for his instructions (that he might change his mind) was no longer applicable then.

When the Tana adds 'u'Vilevad she'Lo Yedameh', he means - that one should not not extrapolate from a given Halachah.

This cannot be a general statement that applies to all areas of Halachah - because that is the way Torah is learned (applying the Halachah from one case to another, via the attribute of 'Binah').

Rav Ashi therefore ascribes it to the area of - T'reifos, where only those T'reifos listed by Chazal are forbidden ...

... because, as the Beraisa explains, there are limbs (such as the junction of nerves) which render the animal T'reifah, if they are severed at a certain point, but Kosher if they are cut to the bone a little higher up (even though more of the limb has been cut off).

Rava instructed Rav Papa and Rav Huna b'rei de'Rav Yehoshua, in the event that they found an error in a ruling of his ...

... during his lifetime - not to tear it up but to bring it to him, and he would either resolve their problem or concede that they were right.

... after his death - neither to tear it up (in case he was right), nor to abide by it (because a Dayan can only go by what he sees ['Ein le'Dayan Ela Mah she'Einav Ro'os']).

He was referring to a ruling that he had written and handed to a litigant, who asked for a written proof of the ruling. Otherwise, the Gemara was not transcribed (until Ravina and Rav Ashi transcribed it).

When Rebbi changed his ruling from the night to the morning, he exclaimed that maybe he had erred. It was not obvious that he had - because in matters that depend on Shikul ha'Da'as (human judgment), there are sometimes two sides to the coin, either of which may be the correct one.

We learn from the Pasuk in Divrei ha'Yamim "ve'Imachem bi'Devar ha'Mishpat" the principle - 'Ein le'Dayan Ela Mah she'Einav Ro'os'.