The rabbis continue to debate the issue of someone who lives in someone else’s property without his knowledge – does he need to pay him rent or not? The gemara bring an argument between Rav and Shmuel and debates exactly what their argument is about and whether or not they are arguing about soemthing the tannaim already debated. A dog or goat who jump off the roof and break vessels is considered typical damage and the owner pays full damage. However if he fell off, the owner would be exempt. This seems to imply that if one started an act with negligence and ended with unexpected damage, one is exempt. The gemara tries to explain how the mishna could fit in with the opinion that holds that if one begins with negligence, one is responsible even if at the end it was not from the negligence.