Shabbat 93a and Shabbat 93b, mostly on the question of shenayim she-asauha, when two people violate Shabbat in unison, and whether their joining in the act means it doesn’t count as a Biblical violation. Also on mesaye’a ein bo mamash, helping in the commission of a sin, where the other person or item could have done it, does not count for Biblical purposes. Closing with a Mishnah about where one item is subordinate to another in an act of carrying.
