The Gemara (Eiruvin 38) says that R' Eliezer holds of Hachana or else one would be allowed to lechatchila make an eiruv on the second day. On the other hand, when R' Chisda says that there is such a ...
Eiruvin 13b records two years-long disputes between Beit Hillel and Beit Shammai, and surely these are not the only long-running debates. How did that work in practice? Did they really have a single ...