Gemara

(R. Chanina of Sura): R. Akiva exempts an animal from Bechorah if it has milk, for most animals do not have milk before giving birth;

R. Yehoshua is concerned for the minority of animals that have milk before giving birth.

Chulin 2a (Mishnah): All (may) slaughter, and it is Kosher...

Question: 'All slaughter' connotes l'Chatchilah. 'And the Shechitah is Kosher' connotes that b'Di'eved!

3b - Version #1 - Answer (Ravina): 'All slaughter', i.e. anyone who knows the laws of Shechitah, even if he is not established (not to weary during the Shechitah);

We must know that he knows the laws. If not, he may not slaughter.

If we do not know whether he knows, and he slaughtered, we test him. The meat is permitted only if he knows the laws.

Version #2 - Answer (Ravina): 'All slaughter', i.e. anyone who is established (to have skilled hands...), even if we are unsure whether he knows the laws.

Four other Amora'im answered unlike Ravina. In Version #1, he permits one to slaughter only if we know that he knows the laws. The others rely on the majority, i.e. most who slaughter know the laws. In Version #2, Ravina permits one to slaughter only if he is established. The others rely on the majority, who do not weary.

Chulin 11b - Objection (Rav Kahana or Rav Simi): Every proof (brought to show that we follow the majority) is a case in which there is no alternative. Perhaps when there is an alternative, we do not follow the majority!

Support: If you would not distinguish, according to R. Meir, who is concerned for the minority, one may not eat meat (lest the animal had a hole where it was slaughtered)!

12a (Rav Nachman): If Reuven saw Shimon slaughter from the beginning until the end, he may eat from the Shechitah. If not, he may not.

Suggestion: Reuven is unsure whether Shimon knows the laws.

Objection: We should say that most who slaughter know the laws (and permit even if Reuven did not see the Shechitah)!

Question (Rav Dimi bar Yosef): If Reuven asked a messenger to slaughter for him and later found the animal slaughtered, what is the law?

Answer (Rav Nachman): He may assume that it was slaughtered properly.

Kidushin 80a (Mishnah - R. Meir): If a child was found near a dough holding a small piece of dough in his hand, the big dough is Tahor;

Chachamim say, it is Tamei, for a child normally plays. (He was Metamei the dough.)

R. Meir joins the minority of children (who do not play) to Chezkas Taharah of the dough; this weakens the majority;

Chachamim ignore the minority. The majority overrides the Chazakah.

Rishonim

Rif (Chulin 3b): A Beraisa is Machshir a chicken found slaughtered in the market, because most who slaughter are experts. The Halachah follows this. Some Rabanan hold like Version #1 (of Ravina), that if we are unsure whether Ploni knows the laws, he may not slaughter. If he slaughtered, we check him. They say that the Halachah follows Ravina, for he is Basra. I disagree, for we hold that most who slaughter are experts. The Gemara concludes like Version #2 of Ravina.

Ran (DH v'Heicha): The Rif and Bahag hold that we rely on the majority only when he went away and we cannot check him. This is because a common minority do not know the laws. This is like Trefos of the lungs. Whenever they are here, we check them. If they are not here, we rely on the majority. Similarly, we do not rely on the Chazakah that houses were checked for Chametz (on Erev Pesach) if we can ask (Pesachim 4a). We said that the other Amora'im did not say like Ravina in Version #1 because they hold that most who slaughter are experts, and not like Version #2, because we are not concerned for weariness. It did not say regarding Version #1 that we are not concerned for amateurs, i.e. and even if he is here we need not check him. This shows that 'most who slaughter are experts' helps only when he is not here, but if he is here, we must check him. This is the Halachah. The Ba'al ha'Ma'or holds that even if he is here, one need not check him. This is wrong.

Rambam (Hilchos Shechitah 4:6): If we do not know whether Ploni knows the laws, and he slaughtered by himself, if we find that he knows the laws, the Shechitah is Kosher.

Rosh (1:5): Ravina (in Version #1) does not hold that most who slaughter are experts. If we are unsure whether Ploni knows the laws, he may not slaughter. If he slaughtered, we check him. If he is not here or they forgot to check, one may not eat from his Shechitah. If one ate, he ate Isur. Therefore, one may not let him slaughter l'Chatchilah, just like a Yisrael Mumar according to Rav Ashi. The Ge'onim explain that the other Amora'im did not explain like Ravina, for they hold that most who slaughter are experts. We let him slaughter l'Chatchilah, on condition to check him afterwards. If he will not be here, or we will forget to check him, the Shechitah is Kosher, for we rely on the majority. However, if he is here, we do not rely on the majority. One may not eat until checking him. There are also other matters in which we rely on the majority only b'Di'eved, e.g. checking the knife after Shechitah and lungs taken by wolves. This is difficult. Why didn't we establish the Mishnah like Ravina, and it discusses experts? I.e. all slaughter l'Chatchilah, even if they are not experts, on condition that we check them later. If he slaughtered and he is not here, the Shechitah is Kosher! It seems that we could not say so, for one may not eat until checking, and 'anyone may slaughter' connotes that it is permitted immediately. The Rif says so.

Tosfos (20b DH Chalav): R. Tam rules that milk by itself does not exempt, for R. Shimon ben Gamliel (24a) exempts only if we see that it has mercy on a calf and nurses it. This shows that we are concerned for a minority when it is supported by a Chazakah (e.g. it did not yet give birth). Even though we do not rule like R. Meir, who joins a minority to a Chazakah even to be lenient (and Metaher - Kidushin 80a), we are stringent. Chulin 11b connotes that only R. Meir is stringent for a minority. However, when a Chazakah supports it, we are concerned. Why don't we join the minority of amateurs who slaughter to the Chezkas Isur of the meat? I answer that the majority who are experts is overwhelming. We find (Gitin 2b) that even R. Meir is not concerned for a miniscule minority, e.g. judges' scribes who do not know that a Get must be Lishmah.

Tosfos (Kidushin 80a DH Semoch): Elsewhere, R. Meir joins a minority with a Chazakah to make an even Safek. Here he joins them to be like a majority (and he is Metaher), because the majority of children who play is flimsy. Chachamim are Metamei only because they consider the child as if he has Da'as (intellect) to ask him. If it were a strong majority, in any case they would be Metamei! Elsewhere, Chachamim ignore the minority and say that the majority is stronger than a Chazakah.

Poskim

Shulchan Aruch (YD 1:1): Anyone may slaughter l'Chatchilah, even if we do not know whether he wearies during Shechitah, or whether he knows the laws. L'Chatchilah one may give to him to slaughter, and one may eat from his Shechitah, for most who slaughter are experts and established (not to weary). This is when he is not here. Then, we rely on the Chazakah and eat from his Shechitah. If he is here, we must check whether he is expert, but one need not ask whether he wearied.

Beis Yosef (DH v'Chasav ha'Rif): The Rif says that we hold that most who slaughter are experts. The Poskim agree. Rashi holds like the Ba'al ha'Ma'or, that therefore we need not check the Shochet. Perhaps Ba'al ha'Itur agrees. The Mordechai and Hagahos Ashri say so. The other Amora'im did not say like Ravina due to the Seifa, for they hold that we need not check him. The Ge'onim (like the Rif and Poskim) hold oppositely, that the Amora'im argue primarily about the Reisha (they let him slaughter l'Chatchilah). However, they argue also about the Seifa. If he cannot be checked, Ravina forbids and they permit, for they hold that we need not check him. The Rashba, Rif, Rosh and Rambam agree with the Ge'onim. The Halachah follows them.

Taz (3): The Or Zaru'a and Ba'al ha'Itur hold that we rely on most who slaughter are experts only b'Di'eved. The Beis Yosef says that they explain that the other Amora'im did not say like Ravina due to the Seifa. This is difficult. If so, they could have established the Mishnah differently! I.e. anyone may slaughter l'Chatchilah if they are experts, and b'Di'eved it is Kosher if we do not know whether the Shochet was an expert, and we need not check him! It seems that the Mishnah connotes that b'Di'eved something else is needed to permit, either checking or another matter. It says 'all may slaughter, and their Shechitah is Kosher.' How can it say about one person l'Chatchilah and b'Di'eved? Rather, l'Chatchilah we must know that he has a certain attribute, and if it was not known, we can find out later.

Shach (4): If a professional butcher ruined the Shechitah, he must bring a proof that he is an expert. (If not, he must pay - CM 306:7.). In such a case we do not say that most who slaughter are experts.

Question (R. Akiva Eiger): If so, if a butcher ruined a Shechitah, it should be forbidden to let him slaughter (some texts - for if he slaughters unsupervised, it is forbidden). We do not find such a law. This requires investigation.

Shach (5): The Bach brings from Ra'avan that even Ravina requires checking him only if he is here. If so, we hold that if he is not here, we may eat from his Shechitah, and we need not pursue him. I disagree. The Gemara said that Ravina obligates checking him. If we cannot, the meat is forbidden if others did not see him slaughter! I can answer that 'he is not here' refers to when we can pursue and catch him, but he is not here now. The Tana of our Mishnah teaches that one need not pursue him. This is difficult. It seems that the other Poskim disagree. According to the Rema, this does not make a difference.

Sifsei Da'as: The Rema says that we demand a Shochet to be certified. Still, Ra'avan's law is relevant, i.e. must we pursue one who slaughtered without certification? Tevu'os Shor says that we forbid his Shechitah, for he transgressed a Cherem of the Tzibur. If so, Ra'avan's law is not relevant.

Gra (3 Likut): The Shulchan Aruch is unlike the Ro'oh, who says that really, everyone (not just the majority) who slaughters is an expert. He was bothered by the question of the Rif and Rosh. They asked from Rav Huna, who says that a living animal (has Chezkas Isur until we know how it was slaughtered). They answered that since most who slaughter are experts, it is as if we know. The Ro'oh rejected this, for in Yevamos we say that the minority joins to the Chazakah. This is wrong. Only R. Meir says so; see Kidushin 80a and Tosfos there. A proof is from Chulin 11b, which said that perhaps we follow the majority only when there is no alternative. R. Meir must say so, for otherwise one may not eat meat (but there was no question why Chachamim permit meat).

Rema: Some say that we rely on the Chazakah only b'Di'eved, but not l'Chatchilah when one can verify it.

Gra (5): This opinion forbids letting one slaughter l'Chatchilah (unless we know that he is expert), but if he slaughtered, one need not check him even if he is here. The Gemara (12) connotes like this, unlike the Sugya above (3b). This opinion would have ruled like Ravina, for he is Basra, if not for 12a.