In the dinim whereby R' Mordechai answers R' Ashi that one is not liable where a cat was overpowered by mice or ate too many, we say that the Shoel is exempt because the cat is not expected to succomb. I generally think of mesah machmas melachah as more similar to where the cat ate a regular amount of mice or lets say tripped and died while chasing mice. If here the cat died because of something that is completely unexpected, why does that not take it out of the context that it happened to have occured while the cat was involved in chasing mice and move it into a geder of ones for which a shoel would be chayav?
michael rubin, brooklyn, ny
Your case would certainly be classified as Meisah Machmas Melachah. However, the Gemara's case should also be included. This is because any case where the borrowed article became damaged through being used for the purpose it was borrowed for is classified as Meisah Machmas Melachah. The fact that it was unexpected that this Melachah would cause this damage does not detract from the Petur. The fact remains that the Sho'el used the cat in the regular manner and it died in the course of its regular work. Had the cat not done this work, it would not have died, so the Sho'el can say to the owner of the cat; "Lav l'Ukmeih b'Chiltah Sh'ilteih"- "I did not borrow it to put it in a bed".