We are continuing in siman 2. The Chayei Adam writes that if a bird flies into a house through an open window, it is assur to shut the window. It is assur even though the act of tzad will only be assur miderabanan, meaning, the bird will still have enough room to fly around such that it cannot be caught in one chase.
The Chayei Adam continues, and writes that it would seem to him that if it is cold outside, or if there is a fear of robbers or wild animals, it would be muttar to shut the window, since the person’s goal is not to trap the animal, but to protect themselves. However, the Chayei Adam is only willing to rely on this heter in cases of tzad miderabanan. Although it is a psik reisha, it is still muttar, as we discussed.
It is not clear from the Chayei Adam whether he holds psik reisha is always muttar on an issur derabanan, or whether he only permits it in the melacha of tzad. The question about whether psik reisha is muttar or assur on an issur derabanan is a machlokes between the Shulchan Aruch and Rema, and the Mishnah Berurah (beginning of siman 314) brings that multiple achronim pasken like the Rema that it is assur. That being said, it is uncomfortable to assume that the Chayei Adam would hold that in general, psik reisha on an issur derabanan is muttar. It is more likely that the Chayei Adam holds that in general, psik reisha on an issur derabanan is assur, with the exception of tzad, where he holds it is muttar.
The Chayei Adam’s reasoning to permit psik reisha in a case of tzad could be based on the Rashba we learned in the previous shiur. While the Rashba applies his reasoning to permit psik reisha even on an issur deoraysa, the Chayei Adam applies it to a derabanan level, in conjunction with the fact that there is tzaar (discomfort) in leaving the window open.
The Chayei Adam continues, and writes that if the bird flies into a house which is small enough that closing the window would be considered an issur deoraysa, it is assur to close the window, even if it is a davar she’eino miskavein.
Summary
There is a question whether it is muttar to perform tzad as a davar she’eino miskavein (ie, for another purpose, but inevitably tzad occurs). The Chayei Adam paskens it will only be muttar in cases of tzad miderabanan, but assur in cases of tzad mideoraysa.
