This is from our Insights to the Daf

www.dafyomi.co.il/shabbos/insites/sh-dt-042.htm

>>Shabbos 42

1) COMPARING "DAVAR SHE'EINO MISKAVEN" TO "MELACHAH SHE'EINAH TZERICHAH L'GUFAH"

QUESTION: The Gemara asks that since Shmuel permits a Davar she'Eino Miskaven, like Rebbi Shimon, he should also permit a Melachah she'Einah Tzerichah l'Gufah. The Gemara answers that the two concepts are not related.

Why does the Gemara initially assume that the two concepts are related when they have entirely different laws? First, a Davar she'Eino Miskaven is permitted on Shabbos, while a Melachah she'Einah Tzerichah l'Gufah is prohibited mid'Rabanan even according to Rebbi Shimon. Second, the concept of Davar she'Eino Miskaven applies to all prohibitions in the Torah, while the concept of Melachah she'Einah Tzerichah l'Gufah is a concept unique to Shabbos, which is derived from the verse of "Meleches Machsheves" (Shemos 35:33). We see that they are two completely independent Halachos. Why does the Gemara compare them?

ANSWERS:

(a) TOSFOS (DH Afilu) explains that whenever a person does an action that unintentionally results in a Melachah being performed (that is, he does a Davar she'Eino Miskaven), by definition the Melachah that results is not Tzerichah l'Gufah (because the person had no need to perform the Melachah). Hence, the Gemara's initial assumption was that the reason why, on Shabbos, Rebbi Shimon permits a Davar she'Eino Miskaven is because even if a Melachah is done unintentionally, it remains no more than a Melachah she'Einah Tzerichah l'Gufah, which he prohibits mid'Rabanan. Similarly, the Gemara assumed that Rebbi Yehudah prohibits a Davar she'Eino Miskaven because of the possibility that it will result in a Melachah that the Torah prohibits, since he considers a Melachah she'Einah Tzerichah l'Gufah to be a Torah transgression.

(b) The TOSFOS HA'ROSH and TOSFOS in Zevachim (92a) explain that the Gemara initially assumed that if a Melachah she'Einah Tzerichah l'Gufah is forbidden, it is because one's intention does not make a difference (that is, even though he did not intend to perform the Melachah for its normal purpose , he is still Chayav). If one's intention does not make a difference, then it stands to reason that not only does not having intention to perform the Melachah for its purpose not make a difference (and he is still Chayav), but not having any intention at all to do the Melachah also does not make a difference.<<

This is from our Background on the Daf-

www.dafyomi.co.il/shabbos/backgrnd/sh-in-042.htm

>>MELACHAH SHE'EINAH TZERICHAH L'GUFAH

When a person performs a Melachah (creative act) on Shabbos intentionally, but does not require the usual result of the action, Rebbi Yehudah rules that he is Chayav and Rebbi Shimon rules that he is Patur. For example, if a person digs a hole not because he needs the hole but rather because he needs the sand, this is a Melachah she'Einah Tzerichah l'Gufah. (See Insights to Shabbos 12:1.)<<