The gemara seems to say that a migo is only acceptable if we are able to interpret his words in a way that lead to a petur. But aren't migos a factor of what you could have said, not what you could have meant? Thank you for your help.
Reuven Pinsky, Waltham, MA
Tosfos explains that this is not a standard Migo. The standard Migo is proof of the truth of his words since had he wanted to lie he would have said a different, more effective claim.
This explanation does not fit the Migo of "Meizid Hayisi." This is because, first, it is a Migo against Edim; we cannot accept his position that he did not eat while Edim say otherwise. Second, he would not have claimed he was Meizid for he does not want to be seen as a Rasha. Therefore, Tosfos explains that we translate his words to mean Meizid, something that he would not have claimed but has the same desired result which is no obligation to bring a Korban.