The Mishna is instructing how to determine if various physical defects make an animal permanently impure and ineligible to be sacrificed while still being permitted for non-sacred consumption. At one point Rabbi Akiva suggests a method of checking a particular defect, in which a lamb seems to have only one testicle. The Gemara then brings a story of a case in which his method was used, yet after slaughtering the lamb it turned out the second testicle was there all along, only not visible. Rabbi Akiva permitted the animal to be eaten, while Rabbi Yochanan ben Nuri forbade the animal to be eaten (as a fistrborn it should have been given to a cohen). This led to a sharp excahnge between the two rabbis:
Rabbi Akiva to Rabbi Yochanan ben Nuri: how long are you going to waste the money of [the people of] Israel?
Rabbi Yochanan ben Nuri to Rabbi Akiva: how long are you going to feed forbidden carcasses to Israel?
the original Hebrew is more pithy:
עד מתי אתה מכלה ממונם של ישראל?
עד מתי אתה מאכיל את ישראל נבילות?
Both scholars start from the same set of facts: the lamb seemed to have a defect, Akiva's proposed method of checking was used and proved the defect was permanent, and the animal was slaughtered based on that tested proposition. Then, they both agree, an external fact, unknowable at the moment of slaughter, was revealed. They differ on the ultimate outcome. Is doing your best enough? Is there an objective commandment which supercedes informed intentions? Do social considerations trump (unknowable) facts? Is there a legal truth which overrides all social measures and intentions?
This deliberation is exactly as fresh today as it was two thousand years ago when Akiva and Yochanan had their altercation; each side brings a set of values which precedes their interpretation of the law and informs it. It's the reason there can be no permanent, immutable and universal legal system: every legal system has to reflect the values of the society which legislated it and applies it and adapts it as the underlying values change.
If you've never visited this blog before, well, now it's too late; I've stopped blogging as described here.