According to Reish Lakish, we understand why R. Shimon exempts (one who swore 'I will not eat Neveilos... ') R. Shimon obligates lashes for eating Mashehu of Isur, therefore the oath does not take effect;

(Beraisa - R. Shimon): One is lashed for eating Mashehu of Isur. The Shi'ur of a k'Zayis pertains only to bringing a Korban.

Question: According to R. Yochanan, why does R. Shimon exempt? (The oath should take effect, for it is Kolel permitted and forbidden food!)

Answer: R. Shimon disagrees with the principle of Kolel.

(Beraisa - R. Shimon): One who eats a Neveilah on Yom Kipur is not liable for eating on Yom Kipur. (Ritzba - the animal died before Yom Kipur. The Isur to eat on Yom Kipur does not take effect on it, even though it forbids all Heter. If an animal dies on Yom Kipur, the Isur of Ever Min ha'Chai goes away, and the Isurim of Yom Kipur and Neveilah both take effect. Others say that even in this case, since it was forbidden to eat before Yom Kipur due to Ever Min ha'Chai (Rashi) or because it was not slaughtered (Tosfos), the Isur of Yom Kipur does not take effect.)

According to Reish Lakish, we understand why he brings a Korban for this oath. The oath could take effect in the positive ('I will eat less than a k'Zayis of Neveilos'; Reish Lakish holds that the Torah permits this) and the negative.

Question: According to R. Yochanan, the oath takes effect in the negative (I will not eat Neveilos or slaughtered animals), but not in the positive (the oath of Sinai already forbids him to eat Neveilos)!

Version #1 - Answer: The oath takes effect in the positive regarding a rotting Neveilah (it is unproper to eat, so the Torah permits it);

We infer from Rava that when one specifies, eating unproper food is considered eating.

Question (Rava): If one swore 'I will not eat dirt', how much dirt must he eat to be liable?

Version #2 - Rashi - Answer #2 (to Question 3:c, 23b): (In both clauses, he said 'I will not eat.') In the Reisha he is exempt, like Rava taught:

(Rava): If one swore 'I will not eat' and he ate dirt, he is exempt.

In the Seifa he is liable, because Neveilos, Treifos... are considered proper to eat (just they are forbidden). (end of Version #2)

Support (Rav Mari - Mishnah): If one swore 'Konam, I may not benefit from my wife if I ate today' and he ate Neveilos... she is forbidden.

Rejection: That is no proof. There is different. Since he ate before swearing, when he swore he considered his act to be 'eating';

Here, when he swears before eating, we have no source that he considers this eating!

(Rava): (Normally, Ein Isur Chal Al Isur (a second Isur does not take effect on something already forbidden.) The opinion that Isur Chal Al Isur when it is Kolel (it also forbids things that were previously permitted) learns from an Isur Mosif (it forbids the forbidden object to more people or in more ways), which is Chal Al Isur;

The opinion that Ein Isur Kolel Chal Al Isur, even though Isur Mosif is Chal, distinguishes. Since Mosif puts new Isurim on the forbidden object, it takes effect also regarding the old Isur;

Regarding Kolel, the fact that new things become forbidden is no reason to put an additional Isur on what is already forbidden.

(Rava): According to the opinion that Isur Kolel Chal Al Isur, if one swore 'I will not eat figs', and later swore 'I will not eat figs or grapes', since the latter oath takes effect for grapes, it also takes effect for figs.

Objection: This is obvious!

Answer: One might have thought that Isur Kolel Chal Al Isur only for Torah Isurim, but not for an Isur (such as an oath) that one made by himself. Rava teaches that this is not so.

Question (Rava brei d'Rabah - Mishnah): One can be liable four Korbanos Chatas and an Asham for eating (slightly more than) a k'Zayis. The case is, a Tamei person ate Chelev that was Nosar from Kodshim, on Yom Kipur;

R. Meir says, if it was also Shabbos and he took the food from a Reshus ha'Yachid and swallowed it in a Reshus ha'Rabim, he is also liable for transferring domains!

Chachamim: That liability is not for eating.

Summation of question: According to Rava, Chachamim can find a fifth Chatas. The case is, he had sworn 'I will not eat figs or Chelev.' Since the oath applies to figs, it applies also to Chelev!

Answer #1: The Tana lists only Torah Isurim, but not what he forbade to himself.

Question: One Chatas is for eating Kodshim while Tamei. He made it Kodshim!

Answer: No, the case is, it was a Bechor (a male firstborn Tahor animal). The Torah made it Kodesh when it was born.

Answer #2: The Tana only lists Isurim that cannot be annulled (but one can annul an oath).

Question: One can annul making an animal Kodesh!

Answer: We already established the case to be a Bechor.

Answer #3: The Tana lists only liability that is Kavu'a (the same for rich and poor people). The Korban for transgressing Shevu'as Bituy is Oleh v'Yored.

Question: The Chatas for a Tamei person who ate Kodshim is an Oleh v'Yored!

Answer: The Mishnah discusses a Nasi. It is like R. Eliezer, who says that a Nasi brings a goat for Tum'ah of the Mikdash or Kodshim

Answer #4 (Rav Ashi): The Tana lists only liability that depends on eating a certain quantity;

One can be liable for an oath for eating Mashehu (if he specifies).

Question: One can be liable for eating Hekdesh, even less than a k'Zayis!

Answer: That also has a minimal quantity. It must be worth a Perutah.

Answer #5 (Rav Ashi of Avirya): The Tana lists only liability for transgressions of Kares (had he sinned b'Mezid). Transgressing an oath is only a Lav.

Question: The Asham is for benefit from Kodshim, which is only a Lav!

Answer: The Tana lists liability for Chata'os only for transgressions of Kares.