2) THE DISPUTE BETWEEN REBBI AVAHU AND REBBI YOCHANAN
OPINIONS: Rebbi Avahu said in the presence of Rebbi Yochanan that one who performs any Melachah in the form of a destructive act (Mekalkel) on Shabbos is exempt, except for an act of Chovel (he wounds a living thing) or Mav'ir (he lights a fire). When Rebbi Yochanan heard this, he said, "Go say that outside the study hall," meaning that there is no place for such a statement inside the study hall. Rebbi Yochanan then said that one is liable only for performing the Melachos of Chovel and Mav'ir when he accomplishes something constructive with the act. For example, one is liable for Chovel when he needs the blood of the animal to feed to his dog, and one is liable for Mav'ir when he wants the ashes of the object he burns. If one merely wounds a creature or lights a fire on Shabbos for no constructive purpose, he is exempt because it is an act of Mekalkel (which is forbidden only mid'Rabanan).

What is the basis of the dispute between Rebbi Avahu and Rebbi Yochanan?

(a) TOSFOS (DH Chovel) quotes RABEINU SHMUEL who explains that Rebbi Avahu follows the view of Rebbi Shimon, who states that "Mekalkel b'Chaburah," one who performs a destructive act of Chovel, is Chayav. Rebbi Yochanan follows the view of Rebbi Yehudah, who states that one is exempt for "Mekalkel b'Chaburah." Only when one does an act of Chovel or Mav'ir which is constructive is he Chayav.

Tosfos has difficulty with this explanation. Why should Rebbi Yochanan reject Rebbi Avahu's teaching ("Go say that outside the study hall") merely because Rebbi Avahu was espousing the view of Rebbi Shimon?

(b) Tosfos explains instead that both Rebbi Avahu and Rebbi Yochanan agree with Rebbi Shimon. They argue merely with regard to Rebbi Shimon's intent when he says that one is liable for Chovel and Mav'ir in any event. Rebbi Avahu takes his statement at face value and understands that Chovel or Mav'ir done in a destructive way is the nature of these Melachos according to Rebbi Shimon. Rebbi Yochanan understands that even Rebbi Shimon maintains that one must have some type of positive purpose in the Melachah in order to be liable for the Melachah. These two Melachos differ from all other Melachos, where Rebbi Yochanan agrees that such a minimal positive purpose is not considered constructive enough to make the person Chayav. For example, it is clearly not considered a constructive act when one makes his friend bleed in order that his dog should have some blood to eat, or when one burns his friend's field in order to have some ashes. Nevertheless, Rebbi Yochanan understands that Chovel is different according to Rebbi Shimon in that even a small constructive purpose renders one Chayav for desecrating Shabbos.

Tosfos asks that Rebbi Avahu's opinion is difficult to understand. How can he suggest that Rebbi Shimon needs no constructive purpose for Chovel and Mav'ir? When done with no constructive purpose, the act is a "Melachah she'Einah Tzerichah l'Gufah" for which one is exempt. (According to Tosfos, a "Melachah she'Einah Tzerichah l'Gufah" is a Melachah that is not done for a purpose similar to the purpose for which the Melachah was done in the Mishkan.) It is apparent from many statements through the Gemara that Rebbi Shimon agrees that every Melachah must be done for some constructive purpose in order for one to be Chayav! Tosfos answers that all of those statements follow Rebbi Yochanan's opinion. Alternatively, Tosfos answers that if one performs an act of Chovel to a living thing from which one is forbidden to derive benefit in order to give to his dog, or he burns it in order to use the fire for cooking, he ruins them totally but for a constructive purpose. (Mordechai Zvi Dicker)