Gemara

(Mishnah): A commoner brings a Se'irah or Kisvah for any Mitzvah punishable by Kares (b'Mezid) and a Chatas (b'Shogeg).

8a (Mishnah): Beis Din is liable only for (permitting) Chayavei Kerisus for which a Chatas is brought (for Shogeg). The same applies for idolatry.

Question: What is the source of this (for Mitzvos other than idolatry)?

Answer #1 (Beraisa - Rebbi): We learn a Gezerah Shavah "Aleha-Aleha" from Achos Ishto (one's wife's sister), which has Kares and Chatas. We learn about individuals from Beis Din. We learn about Beis Din regarding idolatry from "me'Einei-me'Einei" from other Mitzvos. We learn individuals from Beis Din.

Question: Chachamim use "Aleha" to teach about relatives and their co-wives who fall to Yibum. How do they learn all these laws?

Answer #2: They learn like R. Yehoshua ben Levi.

(R. Yehoshua ben Levi): "Torah Achas... for one who sins bi'Shgagah, and for Mezid" equates the entire Torah to idolatry. Just like idolatry has Kares and Chatas, there is a Chatas for Shogeg of other Mitzvos only if there is Kares for Mezid. "Nefesh" teaches about commoners.

Rebbi learned from "Aleha-Aleha." He expounds R. Yehoshua ben Levi's verse to equate a majority that served idolatry b'Shogeg to a minority.

Shabbos 68b (Rav and Shmuel): Even a baby captured by Nochrim is like one who knew about Shabbos and forgot. He brings a Korban for Shabbos;

(R. Yochanan and Reish Lakish): One who knew and forgot is liable. A baby captured by Nochrim or one who converted among Nochrim is exempt.

Question (Beraisa): Anyone who forgot Shabbos entirely and did many Melachos is liable only one Korban, e.g. a baby was captured by Nochrim or a convert converted among Nochrim. He is also liable one Korban for blood...

Munvaz: He is exempt. Regarding Shevu'as ha'Edus, Mezid is called Chotei, just like Shogeg. Just like Mezid knew, also Shogeg.

R. Akiva: If so, you should say that just like Mezid knew at the time he sinned, also Shogeg who knows at the time he sins (is liable)!

Answer: R. Yochanan and Reish Lakish hold like Munvaz.

Munvaz holds that "Torah Achas... bi'Shgagah... b'Yad Ramah" equates Shogeg to Mezid. Just like Mezid knew, also Shogeg. Chachamim expound the verses like R. Yehoshua ben Levi (above).

Munvaz obligates Shogeg even though he knew. His Shegagah was that he did not know that one must bring a Korban for it.

(R. Yochanan): Chachamim hold that Shigegas Korban is not called Shogeg. He must be Shogeg about Kares, even if he knew that there is a Lav;

(Reish Lakish): He must be Shogeg about Kares and the Lav.

Rishonim

Rambam (Hilchos Shegagos 2:6): One is liable if he sinned b'Shogeg and afterwards found out, even if he never knew from the beginning that this is a sin, e.g. a baby captured by Nochrim and raised among them who is unaware of Yisrael and their laws. When he learns that he is a Yisrael and is commanded about the Mitzvos, he brings a Chatas for each Aveirah, e.g. Shabbos, blood...

Kesef Mishneh: The Rambam rules like Rav and Shmuel, for the Gemara challenged R. Yochanan and Reish Lakish from a Beraisa, and answered that they hold like Munvaz. The Rambam holds that really, they hold like Chachamim; the Gemara just meant that someone else holds like them. Also, we can say that they held like Munvaz before hearing the Beraisa. After they heard it, they retracted to hold like Chachamim. We said that they hold like Munvaz lest they be refuted. Even though R. Yochanan and Reish Lakish argued about how to explain Chachamim (69a), which implies that they knew the Beraisa, we can say that this was after they heard the Beraisa. Since they argued about how to explain Chachamim, this is somewhat of a proof that the Halachah follows Chachamim.

Tosfos (Shabbos 69a DH Mah): Chachamim of Munvaz are R. Akiva. We said that he uses the verse to equate the entire Torah to Megadef, i.e. (idolatry). R. Akiva holds that Megadef is blasphemy! We must say that the Gemara answered according to Chachamim who argue with R. Akiva about Megadef, but R. Akiva himself holds that the verse equates the entire Torah to blasphemy. Munvaz learns R. Yehoshua ben Levi's law like Rebbi does.

Aruch l'Ner (Yevamos 9a DH bi'Gemara): If Munvaz learns like Rebbi, we can say that also Rebbi expounds "Torah Achas" like Munvaz (to teach about one who never knew about Shabbos)! The Gemara gave a better answer, for the Beraisa (about a majority who served idolatry) must be like Rebbi, for it is not like R. Akiva, Munvaz or Chachamim. However, in Shabbos, what forced the Gemara to say that R. Akiva expounds the verse to equate the entire Torah to idolatry? This is difficult. Tosfos was forced to give a weak answer for this. Why didn't we say that he expounds like Rebbi, to teach about a majority who served idolatry? This supports an old text of Rashi (Krisos 7a DH Asya), and the Kesef Mishneh says that the Rambam (Hilchos Korban Pesach 2:2) agrees, that R. Akiva holds that Megadef is idolatry, and Chachamim hold that it is blasphemy. This is why it is better to say that R. Akiva holds like Chachamim (that we learn from idolatry) than like Rebbi. This also explains why the Rambam rules like Rav (and Shmuel) against R. Yochanan (and Reish Lakish). The Beraisa about a majority that served idolatry must be like Rebbi, so Rebbi must argue with Munvaz, who used the verse to teach about one who never knew. The Halachah follows Rebbi against his colleague, so the Rambam rules like Rav, who holds like Rebbi, and brought (1:5) Rebbi's Drashah about a majority who served idolatry. R. Yochanan holds like Munvaz, so he must learn that Chatas is for Aveiros of Kares from "Aleha-Aleha", and about co-wives of relatives from "v'Lakchah" and "v'Yibmah" (like Rebbi, Yevamos 8a). This is another reason why the Rambam rules like Rebbi. Even though the Rambam does not rule like R. Yochanan regarding a captured baby, R. Yochanan could expound "Torah Achas" like Rebbi, and he surely does not hold like Chachamim. Therefore, the Rambam rules like Rebbi.

Keren Orah (Horayos 8a DH Nafka): Tosfos (Yevamos 9a DH Mah) asked that since we learn from idolatry, we should say that Chatas is only for Aveiros punishable by stoning! The Yerushalmi asked this, and answered that they learn other Mitzvos from idolatry from a Gezerah Shavah "me'Einei-me'Einei." The Bavli rejects this, for some Isurim of idolatry are forbidden only by a Lav, e.g. hugging and kissing. Therefore, it needed to say that Chachamim learn from Torah Achas. However, stii this is not needed for other Mitzvos! Regarding an individual who serves idolatry, "veha'Nefesh... b'Yad Ramah" teaches that Chatas is only for Aveiros of Kares. We learn the Tzibur from an individual, and to other Mitzvos for the Tzibur from a Gezeirah Shavah "me'Einei-me'Einei", and from the Tzibur to an individual.

Tosfos (ibid.): WHy do we need the Hekesh of Shogeg to Mezid? Even without it, we can learn from "veha'Nefesh... b'Yad Ramah" that Chatas is only for Aveiros punishable by Kares! Rather, we learn from idolatry only what is written in the Parshah.

Keren Orah (DH v'Ra'isi): What was Tosfos' question? If not for "veha'Nefesh... b'Yad Ramah", we would not know that a Korban for idolatry itself is only for matters of Kares! Some Isurim of idolatry are mere Lavim. Perhaps Tosfos asks that since there is a Hekesh, surely it is to teach that Chatas is only for matters of Kares. If it were for all Lavim, the Hekesh would not teach anything! However, if so Tosfos did not need to answer that the Hekesh is only for what is in the Parshah, and say (DH Kegon) that due to this Rebbi and Chachamim argue about whether one must be Shogeg about the Lav and the Kares. (Rebbi says that he must, for he learns from Achos Ishto, and a Lav is written in that Parshah. Chachamim say that he need not, for they learn from idolatry.) This is difficult. If so, both should require "Aleha-Aleha" to require Shegagah about the Lav, and Torah Achas to require Shegagah about the Kares! Rather, both Rebbi and Chachamim only learn (from Achos Ishto and idolatry, respectively) the severity of the Isur (Kares) for which Chatas is brought.

Keren Orah (DH v'Hinei b'Divrei): Where does the Rambam learn that Chatas is only for matters of Kares? He learns from Aleha-Aleha, and not from Torah Achas, for he uses Torah Achas for a majority who served idolatry. Also, he rules (Hilchos Avodah Zarah 2:7) that Megadef is blasphemy, for which there is no Korban. Rather, he learns from Aleha-Aleha, and therefore, he needed to learn (Hilchos Yibum 10:14) the Isur of Tzaros from elsewhere ("Asher Lo Yivneh").

Hafla'ah (Chidushav b'sof ha'Sefer, Shabbos 68b (p. 84b in Sefer) DH Ach): If the Rambam learns from Aleha-Aleha, he should require Shegagah also about the Lav! I answer that the Sugya said that Chachamim expound like R. Yehoshua ben Levi according to Reish Lakish. R. Yochanan obligates a Korban even for one who knew about the Lav. He holds that Chachamim agree that the Hekesh teaches about one who never knew; they argue about Shegagah Korban. Really, they learn from Aleha-Aleha. This would connote that he must be Shogeg about the Lav, therefore, we need the Hekesh of Shogeg to Mezid to obligate even if he knew about the Lav.