1:
Our present mishnah offers several scenarios, but all of them are very simple and present no problems, neither to explain nor to understand.

2:
In the first scenario Sara and David are walking side-by-side in the public domain; Sara is carrying a pitcher and David is shouldering a plank of wood. If Sara's pitcher gets broken by David's plank that is Sara's bad luck. She cannot sue David because both of them have exactly the same right to cross the public domain and neither was in a situation different from the other. David is not liable for the damage done to Sara's pitcher: Sara should have been more careful.

3:
In the second scenario Sara and David are crossing the public domain, but instead of walking side-by-side this time David and his plank are ahead of Sara and her pitcher. Once again, if Sara's pitcher gets broken by David's plank that is Sara's bad luck and she cannot sue David for damages: she should have been aware of the danger to her pitcher and taken the necessary precautions to keep her distance.

4:
The third scenario is the same as the second, but with a difference. David is carrying his plank and behind him - hopefully at a reasonably safe distance - is Sara with her pitcher. Suddenly David stops dead in his tracks. Sara does not have sufficient warning to prevent the inevitable collision and her pitcher is broken by David's plank. Sara can sue David for damages.

5:
Now comes a variation on the third scenario. David does stop suddenly but he also calls out loud and clear "Stop!" This warning is sufficient to avoid a successful case of damages.

6:
The fourth scenario simply reverses the order: Sara with her pitcher is walking in front of David with his plank. If the pitcher is broken by the plank Sara can sue David because David should have taken the necessary precautions to prevent the accident.

7:
Now comes a variation on the fourth scenario. Sara, walking ahead, suddenly stops without warning. David, of course, collides with Sara and the pitcher is broken. Sara has no redress because she was the cause of the accident. However, if she had called out a warning that she had to stop David will be the one responsible for the collision and Sara can sue him.

8:
In order to make sure that we understand that these scenarios are just examples of possible events the last clause of our mishnah simply makes some replacements. Instead of David and Sara we can imagine Sam and Rachel: Sam is carrying a heavy load of flax whereas Rachel is carrying a lantern with a burning candle inside. If the flax is burned by the candle all the possibilities previously detailed by our mishnah will apply.

Tamar Dar writes:

My thoughts are troubled by this question: a person is walking through the public domain carrying a load that unintentionally pollutes the road. As a result of this pollution a pedestrian is injured because he did not notice the hazard. Does the polluter have to pay damages for the damage caused? All this happened in the public domain where everybody has the same right of passage.

I respond:

I am not sure why Tamar refers to pollution in this case because the essence of her question would apply to any kind of hazard. Whether or not the load was placed in the public thoroughfare intentionally or not is irrelevant. We have noted on several occasions that people have the right to use the public domain for their purposes. This is why we established right at the beginning of this chapter that people must look where they are going when they cross the public domain. Tamar has, in fact, in her last sentence answered her own question: it is the person who stumbles over the load left in the road who is at fault; he or she should have looked where they were going.

In BK 018 we had occasion to mention compost and manure. Judith May writes:

I've just raked up masses of oak leaves and deposited them on my backyard compost pile, which, I hasten to add, is in my private domain, so I have a word to say about compost. To make compost efficiently, one must occasionally aerate the material by turning the pile. This is true whether one is composting plant matter, as I do, or manure. It is not a good idea to put fresh, uncomposted manure directly on one's garden, though I don't know if they knew that in ancient times. Isn't it at least possible that the person who turned the manure in this mishnah was tending the pile, which would increase the degree to which he owns the manure?

I respond:

In theory Judith could be right, but I really don't think so. In our scenario the man wanted to take possession of the dung. In order to indicate his possession he must handle it it some way - called in Hebrew meshikhah. The easiest way would be to shovel it into his wheelbarrow, but he does not have his wheelbarrow handy. So the turns over the dung to symbolize his taking possession - and he possibly asks a passer-by to witness what his meshikhah. He can now rush off to get his wheelbarrow and shovel.

I admit, of course, that the man could have been aware of the benefits of aeration, but the whole tenor of the passage suggests to me that what was in his mind was meshikhah pure and simple.