The Talmud records a dispute between R. Shimon and R. Yehudah concerning a melakhah that takes place as an unintended consequence of one’s actions. R. Shimon allows one to undertake an endeavor that will result in a melakhah on Shabbat, as long as that is not one’s intention. R. Yehudah, however, would prohibit such activity; rishonim disagreed as to whether his opinion indicated a biblical prohibition (see Shittah Mekubetzet, Ketubot 5b) or a rabbinical one (see Rashi, Shabbat 121b, Tosafot, Shabbat 41b and Yoma 34b).

Tosafot (Shabbat 110b) cite the Sh’iltot as ruling that R. Shimon’s lenient view is accepted only in regards to Shabbat, which requires a standard of “melekhet machshevet”. The Ri, however, disagrees, and applies this ruling to all areas of the Torah.

R. Chaim (Brisker) Soloveitchik (Chiddushei Rabbeinu Chaim HaLevi, Shabbat 10:17) distinguishes between the notion of “unintentional” as it would apply to the whole Torah, and as it would apply to Shabbat, as a function of melekhet machshevet. The general standard would be a desire and intent (ratzon and kavannah) to bring about the result. Melekhet machshevet, on the other hand, requires just awareness and knowledge (machshavah and da’at).

R. Asher Weiss, however, in a lengthy essay on the topic of melekhet machshevet (Minchat Asher, Shabbat, 55, and al HaTorah, Parashat VaYakhel) develops the thesis that melekhet machshevet is a general concept demanding a standard of “umanut” (craftsmanship) and thus generates many exclusions that are differentiated from each other. Accordingly, he takes issue with R. Chaim’s position, maintaining there is no reason that melekhet machshevet cannot simultaneously demand ratzon and kavannah as well as machshavah and da’at.