If it would teach the case of מציאה only - אי תנא מציאה
Summary:
The משנה teaches that there is a חיוב שבועה even in a case where he (mistakenly) thinks that he is saying the truth. There is certainly a חיוב שבועה when he is definitely a liar. One who is חשיד אממונא is not חשיד אשבועתא.
And let us see; whose money is he holding - ולחזי זוזי ממאן נקט
Summary:
According to רש"י, the question of וליחזי זוזי ממאן נקט means that the מוכר should be asked and believed, even though the item is not in his possession. The גמרא responded that since they both gave money, therefore the מוכר will not be believed and as a result we do not know from whom the מוכר accepted the money willingly. תוספות maintains that the question was that the מוכר should be considered an עד המסייע and therefore exempting one from a שבועה altogether and obligating the other in a שבועה דאורייתא. The גמרא answered the מוכר does not remember. The ר"י explains that we should ask the litigants, and the גמרא answered that the litigants are sure that they both paid but disagree as to whose money the מוכר accepted willingly.
Shall we say that our משנה is not according to Ben Nannos!? - לימא מתניתין דלא כבן ננס
Summary:
Initially the גמרא assumed that even if there is possibility of שבועת שוא, then בן ננס will oppose it. The גמרא concluded that בן ננס is against a ודאי שבועת שוא only, but not a ספק שבועת שוא.
There, both are not grasping it - התם דלא תפסי תרוייהו
Summary:
The רבנן maintain that we rule המע"ה even when there is no actual תפיס, but there is a חזקת מרא קמא, or alternately where אין החלוקה יכולה להיות אמת (and there is a מ"ק).
Where there is a 'Droroh D'mohmoinoh' - היכא דאיכא דררא דממונא
Summary:
A דררא דממונא means that there is a doubt by בי"ד as to the resolution of the matter, without the claims of the litigants. A דררא דממונא should be sufficient cause to warrant a חלוקה (according to סומכוס) without a שבועה.
And if there; where there is a דררא דממונא; and we can assume it entirely belongs to one - ומה התם דאיכא דררא דממונא . ואיכא למימר כולה דמר
Summary:
בן ננס maintains that we do not cause a ודאי שבועת שוא even if the outcome will be an unjustified פסק (as in the case of חנוני על פנקסו and the cases of סומכוס).
And if there; where there is a 'Droroh D'mohmoinoh' - ומה התם דאיכא דררא דממונא
Summary:
Concerning חלוקה the logic of דררא דממונא compels us to have חלוקה despite that אין החלוקה יכולה להיות אמת; however concerning שבועה in a case where אין החלוקה יכולה להיות אמת, there definitely needs to be a שבועה, for דררא דממונא does not contradict it.