I want to defend a basic thesis here. I want to take back what I had written on my other blog about the opinion of the Rambam concerning work done not for its own sake on Shabat.
The original idea was that Rav and Shmuel both say piercing a boil is allowed. Rav says it is allowed because it is the opinion of R. Shimon who holds a work done not for its own sake (מלאכה שאינה צריכה לגופה) is not liable. Since Shmuel says it is allowed and also holds מלאכה שאינה צריכה לגופה is liable; therefore he defines work done not for its own sake (מלאכה שאינה צריכה לגופה) differently. And since the Rambam decides like Shmuel it follows that he goes with Shmuel's definition.
This sounds good but it is not true. Shmuel simply defines those different types of work differently. He puts them into the category of work not intended.
For example: piercing a boil. Rav clearly holds it is a work done not for its own sake (מלאכה שאינה צריכה לגופה). But we see the Rambam explains this as not actually doing work at all. [דבר שאינו מתכווין] He says the only case where there would be work is if it is done in a professional way like doctors. So the Rambam considers this permission to be a case where he is not doing the work at all.דבר שאינו מתכווין[Same with catching a snake--the only work is when it is for a need as the Mishna says openly.]
So what does come out from all this is that the reason piercing a boil is allowed is because it is a work that is not intended דבר שאינו מתכווין and even though Rabbi Yehuda would say in such a case it is liable but the Rambam and Shmuel hold by a work that is not intended דבר שאינו מתכווין that we go by Rabbi Shimon.
This same reasoning applies in Tactate Kritot in the case of stirring coals on Shabat in which case the first Tana says he is liable only once and R. Elazar Ben Tzadok holds he is liable twice. The Talmud says this argument depends on the argument between R Yehuda and R Shimon and that it is a case of work not intended. Tosphot does not see how this can make sense. If it is not pesik reisha [work must occur but his act]
Then even R. Yehuda says it is not liable. If it is pesik reisha [פסיק רישא] then even R Shimon agree it is liable.
Reb Chaim Soloveitchik says, "No." He says it is pesik resiha [פסיק רישא][work that must result automatically] that is not agreeable to him. [[ פסיק רישא דלא ניחא ליה]]In that case R Shimon says it is not liable, and R. Yehuda would say it is. And since the Rambam holds by a work not intended like Shmuel who goes like R. Shimon therefore the Rambam decides like the first Tana!!
What makes my original idea wrong is that no one sees a difference between Rav and Shmuel about the definition of a work done not for its own sake (מלאכה שאינה צריכה לגופה). Also the fact is the Rambam defines it clearly and it is just trying to grasp too much to think that he thinks Rav disagrees with his definition. Like the Talmud says; "Try to grab too much you have not grabbed anything." It is simpler to say Rav and Shmuel are disagreeing about individual cases concerning the question into which category do they fit.
After all the above it does make one wonder why this type of rigorous analysis is not applied to the More Nevuchim of the Rambam?
Elsewhere I explained the actual answer of Reb Chaim--how he expands the category of דבר שאינו מתכווין a act that is not intended.--He has to do that, because otherwise catching the snake seems a lot like a work done not for its own sake (מלאכה שאינה צריכה לגופה. To to this I borrowed an idea from Tosphot.