It seems at one point the gemara speaks of physical exertion as the criterion for what is permissible or forbidden on Chol Hamoed, while later the criterion becomes amateur versus professional. How do we explain this apparent contradiction?
Pesach Rogoway, Israel
Dear Pesach,
I don't see any contradiction in the Gemara. These two things - Tircha - exertion - and Ma'aseh Uman - professional work, are two independent limiting factors that Chazal put on the Heter Melacha of Chol haMoed. In other words, there are certain Heterim for doing Melacha on Chol haMoed, for example Davar haOved or Tzorech haMoed, but Tircha and Ma'aseh Uman can limit these Heterim. For example, watering one's fields is permitted if they will not survive without it, but not if there is a big Tircha involved; one is allowed to sew something that is needed for the holiday but not if it will be done in a professional way.
In some cases Tircha will not be applicable, and in some cases Ma'aseh Uman will not be applicable. For example, writing is forbidden if it is a Ma'aseh Uman (i.e. a Sofer writing STA"M)(see Rambam, Yom Tov 7:13) but writing is not considered a Tircha even when writing professionally. Similarly, watering the fields could be a Tircha if one has to draw water from a well (see Rambam, Yom Tov 8:1), but regardless of where the water is coming from it is not a Ma'aseh Uman. So these concepts are applied in different situations.
Another significant difference between these two concepts is that Tircha can be applied even if no Melacha is involved. For example, Chazal forbid one from moving apartments during Chol haMoed because of Tircha even if one doesn't have to drive his stuff to the new place (see Shulchan Aruch OC 535:1).
Kol Tuv,
Yonasan Sigler
This is not a Peak Halachah