Schach Pasul Part 3

We posted previously on the issue of 4 tefachim of pasul schach rendering an entire succah pasul. I would now like to examine the gemaras on this issue in order to finish explaining the Rambam that we discussed in that post.

There is a halacha that 3 tefachim of airspace in a sukkah's roof pasuls the entire succah. We can pose the following question on this halacha:

How does this law work? One possibility is that the airspace divides the succah in half causing the one succah to now be two separate succahs, each without the requisite 3 walls. Thus, the entire succah is pasul. The other possibility is that the airspace is a psul in the schach. The schach generally all merges together to be one cheftza of schach kosher. If a significant amount of space of three tefachim of airspace exists, we can no longer say that we have one cheftza of schach kosher.

The nafka minah is whether or not the airspace of 3 tefachim has to cut the entire succah in half, or do we say that even a "window" of airspace 3 x 3 tefachim can invalidate the succah. The Rambam clearly says that even windows of airspace invalidate the succah (see hilchos succah 5:9), implying that the airspace is really invalidating the schach, and not dividing the succah in half.

Now, let us pose the same question by schach pasul. I believe that this issue is a machlokes Rav and Shmuel in the gemara.

The first proof to this is that the gemara in succah on 17b when discussing Rav's shitah refers to it as a psul of "haflaga" distancing. This certainly sounds like Rav's opinion is that the succah is divided in half by the pasul schach.

How did the gemara know that this was the sevara of Rav? The gemara earlier suggestes the use of dofen akuma in a situation where there is schach pasul at the side of the succah. This suggestion is made within Rav, and it is my contention that it is only Rav. Shmuel will not agree.

I would like to offer that according to the Rambam, dofen akumah can only fix a psul within the dfanos. Thus, since Rav holds that schach pasul daled divides the succah in half, dofen akumah can then come along and move the dfanos back in place and unite the succah as one. If, however, the schach pasul was invalidating the schach, dofen akumah could not work at all. Dofen akuma is a din in the dfanos.

This approach in Dofen akumah would answer the famous question as to why dofen akumah doesn't work on avir. The Rambam holds that avir invalidates the schach itself, and dofen akumah has no power over that psul.

Thus, the gemara understood, that since Rav is employing dofen akuma in regards to schach pasul, it is clear that Rav is learning the psul as a psul of haflaga.

Shmuel, on the other hand, says schach pasul invalidates the schach itself. For that reason, the gemara says that according to Shmuel even one board of wood 4 tefachim should invalidate the succah (whereas according to Rav this isn't so).

As we explained previously, a board of wood 4 tefachim wide is not a cheftza of schach pasul. Rather, the Rabbis merely did not allow someone to sleep under such schach. The mishna said that such a board of wood does not invalidate the entire succah, and the gemara says this mishna is problematic. The gemara says this only in Shmuel, and I contend that it is davka in Shmuel. Why? Shmuel holds that schach pasul invalidates the schach itself because the schach cannot merge together to be one cheftza of schach kosher.

One can argue in Shmuel that this applies whether the 4 tefachim has a challos shem of schach pasul or not. Why? Because the idea behind Shmuel's psul is that since one cannot use the entire area of the schach to sleep under, so we can't consider it to all be one cheftza. In other words, the psul in Shmuel can certainly be based in the hishtamshus of the schach. If an area of 4 x 4 tefachim of the schach cannot be used the schach is no good.

In Rav, however, we can argue that this is not so. In Rav the 4 tefachim splits the succah in half. In order to do this, the schach as a cheftza must have a challos shem of pasul schach. If not, that schach will merge with all the other schach and connect the various walls of the succah. In Rav's din of merely connecting the walls it is sufficient to have all the schach have one challos shem. In Shmuel, where there is an added halacha that the schach itself is pasul, even a lack of hishtamshus in the schach can pasul it as a "roof".

Therefore, the Rambam, who holds like Rav (as is clear from the fact that he employs dofen akumah by the psul of 4 tefachim) has no problem learning the mishna k'pshuto, that one cannot sleep under a board of wood 4 tefachim, even though it does not actually passul the succah.