Play it safe or play it rational (Chulin 48b)

So here's a question: you find a needle in the lung of an animal. Is it the animal (and lung) kosher or not?

The issue at hand is whether the needle punctured the lung. If it did, the lung is considered traif and thus the animal is not kosher. If it didn't the animal is fine.

What's interesting about this question is that Rabbis Yochanan, Elazar and Chanina permit the animal for eating, while Shimon Ben Lakish, Mani bar Patish, and Shimon be Elyakim say it is traif. That's a pretty big (and even) split.

At the heart of the disagreement is how the needle got into the animal in the first place. There are really only two options. The animal could have swallowed it or aspirated it.

If the animal swallowed it, the needle would have had to have left it's digestive track, puncturing it's intestines (another way an animal become traif) then entered into the lungs by puncturing it from the outside. If the animal aspirated it, the needle would simply have gone down the wrong tube (if there is a right one for a needle!) and the presumption is that it would not have made any holes.

At the root of this debate is whether we privilege rational explanations or halachic certainty. Rationally, it makes much more sense that the needle was aspirated than that it left a cows intestines and found it's way into a lung. That's why Yochanan and his group render the animal kosher. However, Shimon ben Lakish and his group privilege something entirely different. As far-fetched at their scenario may be there is a chance it could have happened. Since the only thing you can be sure about in this situation is that you are not eating non-kosher meat if you prohibit the animal they deem the organ traif and play it safe.

Jewish law is a dance between what is rational and what is safe. Sometimes these two ideals line up. Sometimes, as it does in today's daf, they do not and you must decide which of these two values to privilege.