This Daf is packed with examples of some of the most important principles of Melocho on Shabbos, mainly based on the idea that in order to be biblically forbidden and punishable, an act has to be considered מלאכת מחשבת (a significant, important, or calculated act of work.)

Among them, are the idea that a melacha done in a significantly unusual way (שנוי) is exempt from punishment, as is the rule of two people performing a melacha that could be done by one person ( more on that tomorrow , Hashem willing .)

We have discussed before the concept of מתעסק, where someone who does not have full intention to perform the forbidden act might be exempt .

This, unlike many of the exemptions of מלאכת מחשבת, is derived ( כריתות יט.) from a specific מעוט ( exclusion) in the verse that obligates one to bring a קרבן חטאת for performing a serious transgression unknowingly – “וחטא בה פרט למתעסק” . ( interestingly enough, so is שנים שעשו, right here on the daf)

Yet , despite having its own source, the Gemara in numerous places also states that המסעסק בשבת פטור מלאכת מחשבת אסרה תורה המתעסק בחלבים ועריות חיב שכן נהנה – one who performs a melacha on shabbos without intention is exempt, as the Torah only forbade calculated melacha, but if one eats forbidden fats or sleeps with someone forbidden to him unintentionally, he is liable , as he has derived pleasure from it .

This seems to imply that מתעסק is yet another exemption of מלאכת מחשבת , and not an independent exemption based on its own source .

One can ask further that if the only reason מסעסק is liable by forbidden fats and עריות is because of the pleasure he gets ( a subject for analysis in its own right), then it should apply in ALL areas of halacha where pleasure is not a factor, not only on shabbos , so what is the relevance to מלאכת מחשבת , which is only an exemption on shabbos? ( see Rashi there who asks the question and takes a different approach to what I suggest below, which is more constant perhaps with other Rishonim here , for reasons outside the scope of this post, but that need to be fully studied to get an understanding of this concept.)

It stands to reason that there probably two different kinds of מתעסק or intentional melacha , one category that is exempt in all areas of halacha other than where הנאה ( pleasure) is involved , and one that is only exempt on shabbos .

For example , the classical case of מתעסק where one intends to pick up something detached from the ground and landed up picking up something connected to the ground ( see earlier post on perek 7) , is similar to intending to eating permitted fat and landing up eating forbidden fat, which would be exempt if not for the fact that he derived benefit.

It follows that there is no need for the concept of מלאכת מחשבת to exempt this, as it is covered under the blanket exemption learnt from its own source, which applies in theory to all areas of halacha.

But there is another kind of מתעסק , which we see in the main sugya in כריתות, as well as on our daf today !

This involves a case where one intends to do something that is forbidden, but lands up performing the same forbidden action on a different חפצא ( object ) than intended , or in a different manner (צורה) than intended .

One example subject to debate in the sugya in כריתות is when one intends to light or extinguish a certain candle and lands up lighting or extinguishing a different one .

In other areas of halocho, if one would intend to , for example, bow down to one idol. , and landed up bowing down to another , it is very possible that one would still be liable, seeing as one intended to do the same forbidden action, and there is no exclusion from וחטא בה .

However, on shabbos, the exemption of מלאכת מחשבת is so strong, that it requires a complete fulfillment of נתקים מחשבתו, (his intentions were fully fulfilled .)

Any deviation from this could be a reason for exemption, due to this broader form of מתעסק.

A far -reaching application on this rule is found in a Mishna on our daf!

If one intends to carry something in front of him, and lands up carrying it behind him, even though there is no lack of intent ( מתעסק) in the מעשה ( action), or even in the חפצא ( object of the action), but merely in the צורה ( manner or form of the action), one is exempt!

Rashi explains that this is a form of לא נתקיימה מחשבתו ( his intentions were not fully fulfilled ) which in turn is a form of מתעסק!

[ These posts are intended to raise issues and stimulate further research and discussion on contemporary topics related to the daf . They are not intended as psak halacha ]