We can understand the Sages, but Rabbi Meir's position seems inconsistent: if all roofs are one area, then what does the difference in height of ten hand-breadths matter? - Rabbi Meir is concerned that if people get used to stepping up and down the roofs, they may come to use a mound ten hand-breadths high, situated in a street, for their needs - and there it would clearly be not allowed.

Rabbi Shimon gives a new rule which changes our understanding of the laws of eruv so far: all roofs - and even all courtyards - combine together into one area, and one can carry there - talking about objects which started Shabbat in a courtyard but not in a house. Thus, if an object was in a house at the beginning of Shabbat, the laws and limitations of eruv apply to it. But if it was in a courtyard, then one can take it to another courtyard even without an eruv.

Art: Blue Roofs Rouen by Paul Gauguin (1848-1903)

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