Shabbat 102: Small Acts of Throwing, Carrying and Building on Shabbat

Shabbat 101 is about boats being tied together; smaller boats might be tied between the larger boats.  How are they connected and how can one throw over this private domain without being liable? 

Today's daf begins with a principle taught in a new Mishna: All who are liable to bring sin-offerings are only liable if the beginning of their actions and the conclusions of their actions are unwitting.  If the beginning was accidental and the end was intentional because one became aware of the violation, or if the beginning of the action was intentional but the conclusion is accidental, the the individuals are exempt until both the beginning and the conclusion are unwitting.

The Gemara considers the details of this principal.  These include whether it applies only to actions of carrying but not throwing, as Rava proposes.  The examples used in the Mishna itself are those of throwing (with a dog catching the throw before it lands more than four cubits away).  How can one not know that they are throwing?  The rabbis argue about whether or not there can be "awareness for half a measure".  Other questions around liability for carrying food to one's mouth is also discussed.

We move to Perek XII and a new Mishna.  Building on Shabbat is a primary category of prohibited labour.  How much must be built to be liable to bring a sin offering?  The Rabbis say that one who build in any amount, who chisels, strikes with a hammer or an adze, or drills a hole of any size on Shabbat are liable.  The principle is that anyone who performs a prohibited labour and that labour endures on Shabbat is liable.  Rabban Shimon ben Gamliel says that even one who strikes an anvil with a sledgehammer during his labour has performed a constructive act and thus is liable.  One who improves the labour being performed is the same as one who is doing the primary labour.

The Gemara describes possible acts that might count as building.  Digging holes to hide coins?  Making legs for a small stove to place a small pot on it?  What about sealing a hole in one's house?  Shmuel uses the example of setting a building stone on Shabbat.  But is that actually building?  There are three levels of building: the first row with secured by dirt, the second with mortar, and the third and top row with mere placement.  Similarly, the rabbis argue about making a hole in a chicken coup for ventilation.  But what if the action that might be called "building" is unusual?  We are promised that tomorrow's daf will solve this problem.