Abaye and Rava each found support for their respective positions in a braita - Abaye from the first sentence and Rava from the second. How does each Sage address the proof cited by the other?

The second case in the braita permits a Jew to rely on a Cuti and consume birds strung together, provided the Cuti eats the head of one of the birds on the string. The Gemara raises difficulties with this case: perhaps the Cuti is merely tricking the Jew, or perhaps Cutim do not hold that one must slaughter birds at all, as the requirement is not explicitly written in the Torah.

The Sages resolve the latter difficulty by explaining that Cutim accepted the laws of shechita upon themselves; therefore, they can be trusted even regarding details not explicitly stated in the Torah, including all the ways in which a slaughter can be disqualified. This, however, is a Tannaitic debate: whether or not Cutim can be relied upon regarding laws not mentioned in the Torah that they are known to have accepted. A separate braita is brought to demonstrate this dispute.

Rava holds that one may rely on the slaughter of a person who does not observe the laws of kashrut, specifically one who eats nevelot, provided the knife was checked beforehand. Rava's ruling is based on the principle that a person would rather perform an act in a permissible way than a forbidden way, so long as it does not require significantly more effort. This is proven from a braita regarding the chametz of those who are generally untrusted; one can eat their food after Pesach, relying on the fact that they must have traded their food with gentiles to avoid the prohibition of chametz that remained over the holiday.

A Tosefta is brought to further support Rava's position, but it is subsequently rejected. The Gemara explains that the Tosefta refers to a person who worships idols, rather than one who merely consumed non-slaughtered meat. This reading is supported by a statement of Rav Anan in the name of Shmuel that one can trust the meat of a person who worships idols. The source for this is the biblical figure Yehoshafat, who ate from Achav's meat in an incident that appears in Chronicles II, Chapter 18. The Gemara raises several difficulties about deriving this law from that incident, but all difficulties are eventually resolved.