Daf Yomi - Sukkah 33 - Letters on the Side of a Book on Shabbos

The Mishna ruled that if there are more berries than leaves on the hadas, it is invalid. One can remove the berries before the festival but one is forbidden to remove the berries on the festival. The reason for this ruling is because removing the berries is deemed to be repairing the hadas, and one is prohibited from repairing a utensil on the festival. Rabbi Eliezer maintains that it would be permitted to remove the berries on the festival. The Gemara qualifies this ruling to be referring to a case where he plucked the berries with the intention of eating them. Rabbi Eliezer permits this because he rules in accordance with the opinion of his father Rabbi Shimon who maintains that one is permitted to perform a permitted act although he may unintentionally perform a forbidden act in the process. An example of this is when one drags a chair across the dirt on Shabbos where he may make a furrow in the ground. His intention is to move the chair and not to cerate the furrow, so even though he is aware that he may cerate a furrow, Rabbi Shimon maintains that this is permitted. The Gemara questions this because even Rabbi Shimon agrees that if the prohibition will inevitably occur, it is forbidden to perform the permitted act. The Gemara answers that we are referring to a case where the person has another hadas and when he plucks the berries from this hadas, he does not care whether the hadas is valid. Thus, we do not deem the plucking of the berries to be a repair and he has not committed a prohibited act at all.Tosfos explains that the answer of the Gemara is predicated on the principle of melacha sheaina tzricha legufa, an act that was not performed for a defined purpose. Normally we say that it is rabbinically prohibited to perform an act where one does not desire the forbidden outcome. However, when there is a mitzvah involved, one is permitted to perform the act outright. [Tosfos seems to maintain that the person plucking the berries has intention for the mitzvah.] Teshuvos Imrei Yosher rules based on the words of Tosfos that one would be permitted to study on Shabbos from a sefer that has letters and words on the side of the pages. This would be permitted even though when he turns the pages he is in effect forming or erasing words. The reason for this ruling is because when one is preoccupied with a mitzvah, the Chachamim were not concerned with the prohibited act that will result if the result is unintended and undesired. The Mishna Berura rules that one can even read from a book with letters on the side even if he is not engaged in Torah study. The reason for this ruling is because one is not deemed to be writing or erasing as the pages of the book are meant to be turned. This would be analogous to opening and closing a door which would not be deemed building or destruction because a door is meant to be opened and closed.