The Eri B. Sitt Edition and Audio Series of the Talmud Bavli, Tractate Sukkah, has been dedicated by Celia and Isaac Jamal—may God preserve them and grant them life— for the success of their dear children. May they derive much joy from all of them; may they all grow up, marry at the proper time, and have healthy, happy children with blessing and success. May Celia and Isaac see descendants and the descendants of their descendants, until the coming of the righteous redeemer. Amen.
The tractate has also been dedicated for the elevation of the soul of Sara bat Adel, may God avenge her blood and grant her rest in the Garden of Eden. Amen. Again, this dedication is by Celia and Isaac Jamal. May they merit to perform many mitzvot. Amen.
Today's page has been generously sponsored by Mr. Harry Ajmi in honor of the premier caterer and our dear friend, Mr. Uri Nidan. We congratulate Uri on the birth of a baby girl. May he derive much joy from all his children and see them grow in the fear of God. Amen.
Page ten is being studied for the elevation of the soul of Abraham ben Esther. May the spirit of God preserve him and grant him rest in the Garden of Eden. Amen. Today's page has also been dedicated by Mr. Harry Ajmi and his family in honor of his dear friend, Mr. Uri Nidan. May God preserve them and grant them life. Amen.
We begin today's page on 9b, two lines from the bottom, with the words, “Sometimes.” Let us briefly review where we left off.
At the end of yesterday's page, we quoted the opinion of Rabbi Yirmiyah concerning one sukkah beneath another sukkah. To keep the image in mind, imagine two sukkot, one on the bottom and one above it. Rabbi Yirmiyah presented four cases: sometimes both sukkot are valid, sometimes both are invalid, and sometimes one is valid while the other is invalid—either the upper sukkah or the lower one.
The Gemara now explains each scenario. The first case is when both sukkot are valid. How is that possible? The lower sukkah has more sun than shade, while the upper sukkah has more shade than sun. In addition, the upper sukkah is within twenty cubits of the ground of the lower sukkah. Therefore, a person may sit in either sukkah. If he sits in the lower sukkah, he relies on the roofing of the upper sukkah, because the roofing above him has more sun than shade and therefore does not disqualify the lower sukkah. If he sits in the upper sukkah, that sukkah is also valid because it is within twenty cubits and has more shade than sun.
The second case is when both sukkot are invalid. The upper sukkah is above twenty cubits from its own floor. Therefore, one may not sit in the upper sukkah, even though its roofing has more shade than sun and would otherwise be perfect. Since the distance from its floor to the top of the sukkah is more than twenty cubits, it is invalid. The lower sukkah is also invalid because it has more shade than sun, and above it there is another sukkah that has more shade than sun. A person sitting in the lower sukkah is therefore sitting beneath two roofs, and that is not permitted.
The Gemara then says: “Sometimes the lower sukkah is valid and the upper sukkah is invalid.” What is the case? The lower sukkah has more shade than sun, while the upper sukkah has more sun than shade. Both sukkot, however, are within twenty cubits.
We have to understand what the Gemara gains by emphasizing that both are within twenty cubits. If the lower sukkah is valid, that is obvious. To make the upper sukkah invalid, it is sufficient that it have more sun than shade. What difference does it make whether the upper sukkah is within twenty cubits? Even if it were above twenty cubits, it would also be invalid.
To understand this, we must read Rashi. Rashi explains that the roofing of the upper sukkah has more sun than shade, and therefore is not considered valid roofing. Consequently, the lower sukkah is not regarded as a sukkah beneath another sukkah, because the upper structure is not a valid sukkah. Both are within twenty cubits so that the upper roofing is not invalid because of its height; it is invalid only because it has more sun than shade.
Rashi's explanation here represents a significant reversal of the position we discussed yesterday. Yesterday, in the case of a tree above a sukkah, Rashi understood that if the tree itself had more sun than shade and the valid roofing of the sukkah also had more sun than shade, together they could produce more shade than sun. The Gemara challenged this: how can valid roofing be created by combining it with material that is attached to the ground and is therefore invalid? The answer was that when the branches are intermingled with the valid roofing, the principle of nullification applies. Since the majority is valid and the invalid material is the minority, the result is valid.
Rashi went out of his way to understand the case in that manner. His explanation implied that if the lower sukkah already had more shade than sun, whatever was above it would not affect it. Even if the tree above had more sun than shade, the lower sukkah would remain valid, because the lower sukkah was already valid on its own and was not relying on a combination of materials.
Here, however, Rashi reverses that position. In our case, the lower sukkah has more shade than sun and is otherwise excellent, while the upper sukkah has more sun than shade and is therefore invalid. Rashi nevertheless emphasizes that the upper sukkah is within twenty cubits. If the upper sukkah were above twenty cubits, its roofing would be invalid roofing, and it would combine with the valid roofing of the lower sukkah in a way that would invalidate it.
How can that happen? Why must we take the upper roofing into account at all? One might say that the upper roofing should simply be ignored. The lower sukkah is valid on its own; let us regard the upper roofing as nonexistent.
The early commentators explain the dynamics as follows. We regard the lower sukkah as having a section of invalid roofing hovering above it. To use an analogy, it is as though the invalid roofing burns a hole through the valid roofing beneath it. The invalid roofing fills that area and eats away at whatever is underneath it. Thus, although the lower sukkah originally had more shade than sun, the invalid roofing above it can destroy the valid roofing beneath it. If enough of the lower roofing is thereby removed, the lower sukkah becomes invalid.
The Ba'al HaMa'or points out that this applies only when the invalid roofing above removes enough of the lower roofing to cause the lower sukkah itself to have more sun than shade. If the invalid roofing is positioned in such a way that, even after accounting for the area it displaces, the lower sukkah still has more shade than sun, then the lower sukkah remains valid. The case must therefore be one in which the upper roofing removes enough of the lower roofing to invalidate it.
We therefore see that Rashi has reversed the position we understood yesterday. Yesterday, we thought that once the lower sukkah had more shade than sun, nothing above it mattered. A tree above it could be ignored, because the lower sukkah was already valid without it. Here Rashi says that even if the lower sukkah is valid, one must still deal with what is above it. If the upper roofing is invalid, it can affect the lower sukkah. That is why the Gemara specifies that, in this case, the upper sukkah is within twenty cubits. It is invalid because it has more sun than shade, not because it is invalid roofing due to excessive height.
The Gemara then presents the final case: sometimes the upper sukkah is valid and the lower sukkah is invalid. Both sukkot have more shade than sun, and the upper sukkah is within twenty cubits. That explains why the upper sukkah is valid. The lower sukkah is invalid because a person sitting there is beneath one sukkah and then beneath a second sukkah. We learned yesterday that one may not have a sukkah beneath another sukkah, because the Torah requires a person to sit in one sukkah. Therefore, the lower sukkah is invalid.
The Gemara asks: Is this not obvious? All the cases Rabbi Yirmiyah presented seem logical. It is useful that he stated them, but when the Sages teach a halachah, there is generally an element of novelty—something we would not have known without their statement. What novelty is there in these cases?
The Gemara answers that without Rabbi Yirmiyah, I might have thought that one of the cases would be invalid: the case in which the lower sukkah has more shade than sun and the upper sukkah has more sun than shade, with the upper sukkah within twenty cubits. I might have said that even this case should be invalid. Why? If we permit a person to sit in the lower sukkah when the upper sukkah is within twenty cubits, someone may mistakenly sit in the lower sukkah when the upper sukkah is above twenty cubits.
When a person looks up and sees that the upper roofing has more sun than shade, he may think it is insignificant and pay no attention to it. But if that roofing is above twenty cubits, it is not merely insignificant; it is invalid roofing. It can then combine with the valid roofing of the lower sukkah and create a problem. I might therefore have thought that the Sages would establish a decree and invalidate the lower sukkah in every such case, whether the upper sukkah was within twenty cubits or above twenty cubits.
Rabbi Yirmiyah teaches that we do not make that decree. When the upper sukkah is within twenty cubits, the lower sukkah is valid. Only when the upper roofing is above twenty cubits does it become invalid roofing that can combine with the valid roofing below it.
Rashi explains that one might have thought that the lower sukkah should be invalid whenever the upper sukkah is above twenty cubits, because a person would not necessarily recognize the problem. Seeing that the upper sukkah has more sun than shade, he might say, “It is nothing,” and fail to realize that, because it is above twenty cubits, its roofing is now invalid and can combine with the valid roofing of the lower sukkah. Rabbi Yirmiyah's novelty is that we do not make this decree.
Thus, of the four cases, three are obvious. The novel case is that when the lower sukkah has more shade than sun and the upper sukkah has more sun than shade, one may sit in the lower sukkah if the upper sukkah is within twenty cubits. One might have thought that the entire case should be prohibited because of the possibility that people would make a mistake when the upper sukkah is above twenty cubits. Rabbi Yirmiyah teaches that we do not make such a decree.
The Gemara now asks a fundamental question: how much space must there be between two sukkot for the lower sukkah to be invalid because the person is sitting beneath two sukkot? Suppose the upper sukkah is suspended only half a millimeter above the lower sukkah. Is that already considered a separate sukkah, or must there be a significant space between them?
Rav Huna says that a handbreadth is sufficient. Once there is a handbreadth or more between the two sukkot, the upper structure is considered a separate domain, and the person is sitting beneath a sukkah beneath a sukkah. Anything less than a handbreadth is not significant.
From where does Rav Huna derive the measure of a handbreadth? The Gemara finds this measure in the laws of ritual impurity. The Mishnah teaches that a structure one handbreadth by one handbreadth, with a height of one handbreadth, conveys impurity and interposes before impurity. Let us illustrate the case.
Imagine a roof or ledge. There is a space of one handbreadth between the top of the ledge and the floor below it. Beneath the ledge is a portion of a corpse measuring an olive's bulk. Beside the corpse, under the same roof, there is a utensil. The utensil becomes impure even though it does not touch the corpse, because when there is a roof over the corpse, the impurity spreads throughout the area under that roof.
If, however, the utensil is placed above the roof, it remains pure. A space of one handbreadth has the status of an enclosure or tent for the laws of impurity. The impurity spreads throughout the area beneath the roof, but the roof blocks it from rising above. Thus, the one-handbreadth structure conveys impurity to what is underneath and interposes before impurity with respect to what is above.
When the space is less than a handbreadth, the law is different. The corpse is considered to be in a compressed space, and the impurity shoots directly upward through the roof. In that case, a utensil placed above the roof becomes impure, because the impurity breaks through. A space of less than a handbreadth does not constitute a significant enclosure.
Rav Huna applies this principle to sukkah. A handbreadth is already a significant measure for creating an enclosure in the laws of impurity. Therefore, if there is at least a handbreadth between the lower sukkah and the upper sukkah, the upper roofing is considered a separate structure. The person is sitting in the lower sukkah while another sukkah, in the form of a separate enclosure, is above him. Anything less than a handbreadth does not create that separation.
The next opinion is that of Rav Chisda, who says that four handbreadths are required. One handbreadth is not sufficient. There must be a space of four handbreadths between the lower sukkah and the upper sukkah for it to be considered a significant sukkah beneath another sukkah.
From where does Rav Chisda derive four handbreadths? The Gemara says that we do not find a significant area in halachah that is less than four handbreadths. This measure appears in Tractate Shabbat, where we learned about the various domains. For an area to constitute a distinct domain, it must be four by four handbreadths. That shows that four handbreadths is considered a significant area.
This derivation is somewhat difficult, because those measures concern length and width, whereas here we are looking for a measure of height. Tosafot address this issue and point to a case in Tractate Eruvin. Two courtyards are adjacent to one another and separated by a windowsill. The Gemara says that if the windowsill is four handbreadths high, the two courtyards are considered separate; if it is less than four handbreadths, the courtyards are considered joined. We therefore find that four handbreadths is significant in height as well.
The third opinion is that of Shmuel, who says that there must be ten handbreadths. His principle is that just as the minimum size of a valid sukkah is ten handbreadths, so too the minimum measure required to invalidate the lower sukkah is ten handbreadths. If there are ten handbreadths from the lower sukkah to the upper sukkah, the upper structure has the status of a sukkah, and the lower one is a sukkah beneath another sukkah.
The Ritba raises an obvious question against Shmuel. Shmuel says that the upper structure must be ten handbreadths high because ten handbreadths is the minimum height of a valid sukkah. But a sukkah above twenty cubits is invalid. What do we say in that case? We nevertheless refer to it as a sukkah, even though it is invalid because it is too high.
The explanation is that the reason a sukkah above twenty cubits is invalid is that it is considered a permanent structure. It is still a sukkah; it is simply a permanent sukkah, and that permanence is what disqualifies it. Therefore, even a sukkah above twenty cubits has the status of a sukkah for this purpose. Certainly, if it is placed above a temporary sukkah, it creates a sukkah beneath a sukkah.
By contrast, a structure less than ten handbreadths high is not considered a sukkah at all. That is why Shmuel requires a separation of at least ten handbreadths between the lower and upper sukkot.
We therefore have three opinions concerning the separation between the lower and upper roofing needed to create a sukkah beneath a sukkah: Rav Huna requires one handbreadth, Rav Chisda requires four handbreadths, and Shmuel requires ten handbreadths.
The Gemara then cites a Mishnah. Rabbi Yehuda says that if no one dwells in the upper sukkah, the lower sukkah is valid. Rabbi Yehuda appears to hold that the lower sukkah is valid only when there are no residents in the upper sukkah.
What does it mean that there are no residents? It cannot mean that no actual people live there. Why should it matter whether people are physically dwelling in the upper sukkah? What new rule would that create for the lower sukkah?
The Gemara explains that “there are no residents” means that the upper sukkah is not fit for residence. We must now determine why it would not be fit for residence. One possibility is that it is less than ten handbreadths high. Rabbi Yehuda would then be saying that if the upper sukkah is less than ten handbreadths high and therefore unfit for dwelling, the lower sukkah is valid.
On this reading, Rabbi Yehuda is arguing with the Sages. Rabbi Yehuda holds that when the upper sukkah is less than ten handbreadths high, the lower sukkah is valid. The Sages would apparently hold that even when the upper structure is fit for dwelling—meaning that it is ten handbreadths high—the lower sukkah is valid.
But this creates a difficulty. Shmuel just taught that the upper sukkah must be ten handbreadths high for the lower sukkah to be invalid. How can the Sages say that even when the upper sukkah is less than ten handbreadths high, the lower sukkah is invalid? That would contradict Shmuel's position.
When Rav Dimi came from the Land of Israel to Babylonia, he said that in the West they explained the matter differently: a subordinate statement cannot properly be understood unless it can accept both the favorable and unfavorable consequences of the position being attributed to it.
Rav Dimi explains that “not fit for dwelling” does not refer to the height of the upper sukkah. The upper sukkah really does need to be at least ten handbreadths high for the lower sukkah to be invalid. The phrase refers instead to the strength of the floor of the upper sukkah.
The upper sukkah may be ten handbreadths high, but its floor may be too weak to support a person sleeping there with a bed, pillows, blankets, and all the other articles necessary for residence. Rabbi Yehuda teaches that if the upper sukkah cannot support those things, the lower sukkah is valid. The issue is not the height; everyone agrees that the upper structure must be ten handbreadths high for it to invalidate the lower sukkah.
The novelty of Rabbi Yehuda's position is that the upper sukkah must be sufficiently sturdy to support a bed and the other articles of residence. If it cannot support them solidly, the lower sukkah remains valid. The Sages disagree and hold that even if the upper floor can support a bed only precariously or with difficulty, it is still considered fit for dwelling, and the lower sukkah is invalid.
The Gemara then asks what follows from this disagreement. If the Sages hold that an upper sukkah is considered fit for residence even when it can barely support a bed, they should also hold that a structure less than ten handbreadths high can invalidate the lower sukkah, because such a structure is likewise not fit for residence. That would contradict Shmuel, who requires ten handbreadths.
The answer is that the issue of ten handbreadths is separate. Everyone agrees that the upper structure must be ten handbreadths high to have the status of a sukkah. The disagreement between Rabbi Yehuda and the Sages concerns only whether the floor must be strong enough to support the articles of residence solidly. Rabbi Yehuda requires a sturdy floor; the Sages are more lenient and consider it sufficient if the floor can support those articles, even imperfectly. Shmuel's requirement of ten handbreadths remains valid.
The Gemara now begins a new Mishnah. It discusses a person sitting in a sukkah who spread a sheet over the roofing to protect himself from the sun. Alternatively, he placed a sheet beneath the roofing to catch leaves and other debris falling through. A third case is when he spread a sheet over a structure called a canopy bed.
A canopy bed has a flat bed with four posts rising from its corners. Crossbars connect the posts, and a sheet is draped over the top, creating a roof. The Mishnah says that in these cases the sukkah is invalid. However, one may sit beneath a structure called a bed with two posts. In that case, one post is near the head of the bed and one near the feet, with a crossbar above them. The sheet drapes down like a tent rather than forming a flat roof.
The Mishnah distinguishes between the four-post canopy bed and the two-post structure. We will analyze the reason for the distinction.
When the sheet is placed beneath the roofing to catch leaves and debris, it is invalid. If, however, the sheet is placed there for decorative purposes, the sukkah remains valid. What is the difference? In both cases the person is sitting beneath a sheet rather than directly beneath the roofing.
Rashi explains that when the purpose is to protect the person from falling debris, the sheet functions as a roof. The very purpose of a roof is to provide protection. Since the sheet is being used for protection, it is regarded as invalid roofing, and the person is sitting beneath invalid roofing. When the sheet is placed only for decoration, it is not functioning as a roof, and the sukkah remains valid.
Thus, the intention with which the sheet was placed makes a difference. Two sukkot may look exactly the same: in both, a sheet is beneath the roofing. One is valid and the other is invalid, depending on whether the sheet was placed for decoration or for protection. The same applies to placing a decorative net or other ornamental material, provided that it is genuinely being used for decoration.
This discussion assumes that the original roofing itself has more shade than sun and is therefore valid. Tosafot understand the case differently. According to Tosafot, the roofing initially has more sun than shade, and the sheet beneath it combines with the roofing to produce more shade than sun. The problem is that valid roofing is being created through a combination of valid and invalid materials.
Tosafot cite the responsa of the Geonim and explain that the sheet is invalid only when, without it, the sukkah has more sun than shade, and adding the sheet creates the required majority of shade. If the roofing already has more shade than sun on its own, the sheet does not invalidate it. The valid roofing remains valid, and the sheet does not affect it.
This returns us to the issue of the tree above the sukkah. Tosafot clearly state that once one has valid roofing with more shade than sun, nothing placed above or beneath it can invalidate it. Rashi, however, as we explained earlier, holds that invalid roofing next to valid roofing can eat away at it and affect the sukkah. Accordingly, the same disagreement between Rashi and Tosafot appears here.
According to Rashi, the case is one in which the sukkah's roofing is already perfect, and the question is whether the sheet was placed beneath it for decorative purposes or for protection. If it was placed for protection, the person is sitting beneath invalid roofing. According to Tosafot, the problem exists only when the sheet combines with roofing that is initially insufficient, creating a valid sukkah through the combination of valid and invalid materials.
The Gemara asks whether this ruling is not obvious. If the sheet was placed for decorative purposes, of course the sukkah should be valid. The Mishnah already says that the sheet is invalid when it is placed to catch debris, implying that when it is placed for decoration it is valid.
The Gemara answers that one might have thought that even a decorative sheet is prohibited. Perhaps the Mishnah mentions the ordinary case—catching debris—because that is the usual reason a person puts a sheet beneath the roofing, but perhaps both purposes should be prohibited. Rav Chisda teaches that the Mishnah mentions catching debris because that is the only case that is invalid. When the purpose is decorative, the sheet is valid.
The Gemara then seeks a proof. We learned that a person may decorate the sukkah with embroidered sheets, ornamental sheets with raised designs, and picturesque fabrics. One may also hang from the sukkah nuts, almonds, peaches, pomegranates, bunches of grapes, crowns of grain, cups of wine, cups of oil, fine flour, and other decorative items.
The novelty of that teaching is that one may not benefit from these items during the festival. If a cup of wine was hung from the sukkah as a decoration, one may not simply remove it and drink it during the festival. When the items were placed there, they were designated for the sukkah, and they may not be used until the festival is over. If the person made a condition before hanging them that he would be permitted to use them whenever he wished, that condition permits their use.
What do we see from this? Non-roofing materials may be hung from the sukkah for decorative purposes. That appears to prove that placing a sheet for decoration is also permitted.
The Gemara rejects the proof. Perhaps the decorations mentioned in that teaching were placed on the sides of the sukkah, not beneath the roofing. The teaching may permit decorating the walls, while a sheet placed beneath the roofing could still be invalid.
The Gemara brings another teaching concerning sukkah decorations. When a person places decorations in the sukkah, they do not reduce the height of the sukkah. Suppose the sukkah is higher than twenty cubits, but decorations hang beneath the roofing, so that the distance from the bottom of the decorations to the floor is less than twenty cubits. We do not measure from the decorations; we measure from the actual roofing. The decorations do not make the sukkah valid.
The same is true in the other direction. If a sukkah is ten handbreadths high and decorations hang beneath the roofing, so that the distance from the decorations to the floor is less than ten handbreadths, the decorations do not invalidate the sukkah on that account. In measuring the height, we do not factor in the decorations.
Rav Ashi adds that this is true only with respect to height. Decorations hanging from the sides can reduce the usable area of the sukkah. The minimum area of a sukkah is seven by seven handbreadths. If decorations take up enough space along the sides that a person can no longer live comfortably within the remaining area, they can invalidate the sukkah by reducing its length or width.
The rule is therefore that decorations do not affect the height of the sukkah, whether the issue is the maximum height of twenty cubits or the minimum height of ten handbreadths. They can, however, affect the length and width if they reduce the usable area below the minimum.
The Gemara tells a story about Min Yamin, the servant of Rav Ashi. Min Yamin's cloak became soaked in water. He went to dry it by spreading it over the sukkah. Rav Ashi told him to remove it, because people might see the rabbi's garment spread over the sukkah and conclude that ordinary cloth could be used as roofing.
Min Yamin responded that no one would make that mistake. They would see that the garment was soaking wet and understand that it had been placed there temporarily to dry. Rav Ashi nevertheless said that while the garment was wet, he was not concerned; people would understand its purpose. Once it dried, however, it had to be removed, because people might then think that the garment had been placed there as roofing.
The Gemara then discusses decorations that hang down from the roofing. If the decorations are separated from the roofing by four handbreadths, there is a disagreement. Rav Nachman says that the sukkah remains valid. Rav Chisda says that once the decorations hang down four handbreadths, they constitute a separate domain, and a person sitting beneath them is sitting beneath the decorations rather than beneath the roofing.
According to Rav Chisda, four handbreadths create a separation. When the decorations are close to the roofing, everyone agrees that they are subordinate to the roofing. A sukkah may be completely decorated with grapes, to the extent that the actual roofing cannot be seen, and the sukkah is still valid, because the decorations are accessories to the roofing. But once they hang down four handbreadths, Rav Chisda considers them an independent structure. Rav Nachman maintains that they remain subordinate to the roofing regardless of how far they hang.
The Gemara tells another story. Rav Chisda and Rava visited the Exilarch during the festival. The Exilarch placed them in a sukkah whose decorations hung down less than four handbreadths. Rav Chisda's own opinion was that such a sukkah was invalid. Nevertheless, the rabbis remained silent.
It might appear that they had retracted their position, but they explained that they were on a mission to perform a mitzvah. The Gemara later teaches that people traveling to perform a mitzvah—such as visiting one's rabbi or rescuing captives—are exempt from the mitzvah of sukkah while engaged in that mission. They were therefore not required to spend time building or finding another sukkah, and their silence did not indicate that they had changed their opinion.
Rabbi Yehuda said in the name of Shmuel that it is permitted to sleep beneath a canopy bed in a sukkah, provided that the canopy is less than ten handbreadths high. Although it has a roof and appears to create a separate structure, anything less than ten handbreadths is not considered a separate domain.
The Gemara challenges this from another teaching: a person who sleeps beneath a canopy bed in a sukkah has not fulfilled his obligation. The Gemara answers that the teaching is referring to a canopy that is ten handbreadths high or more. At that height, it constitutes a separate domain, and the person is sleeping beneath the canopy rather than beneath the sukkah's roofing. If it is less than ten handbreadths, he fulfills his obligation.
The Gemara asks about someone who sleeps beneath a regular bed in a sukkah. The answer is that the bed is more than ten handbreadths high. If the space beneath it were less than ten handbreadths, it would not constitute a separate domain, and sleeping there would be comparable to sleeping beneath a canopy of less than ten handbreadths.
The Gemara returns to our Mishnah, which says that if a person spreads a sheet over a four-post canopy bed, the sukkah is invalid, while a sheet spread over a two-post structure is permitted. A teaching explains that a two-post bed has two posts, one near the head and one near the feet, while a four-post canopy bed has four posts. If a sheet is spread over the four-post canopy, it is invalid; if it is spread over the two-post structure, it is valid.
The Gemara initially understands the distinction to depend on height: a two-post structure is valid when it is less than ten handbreadths high and invalid when it is ten handbreadths or higher. But the teaching appears to imply that even a four-post canopy less than ten handbreadths high is invalid. How can that be, if we have just said that less than ten handbreadths does not create a separate domain?
The Gemara answers that the four-post canopy bed is different because it is a permanent, sturdy structure. Its permanence gives it the status of an independent enclosure even when it is less than ten handbreadths high.
We therefore have three different structures: a canopy bed, a two-post bed, and a four-post canopy bed. The canopy bed is not a permanent structure. It is a temporary arrangement, and when it is less than ten handbreadths high, it does not create a separate domain. When it is ten handbreadths or higher, it is invalid because it does create a separate domain.
The two-post structure has no actual roof, but it has a certain degree of permanence. It is invalid when it is ten handbreadths or higher, but valid when it is less than ten handbreadths.
The four-post canopy is the most permanent structure. Because it has a roof and is considered sturdy and established, it is invalid even when it is less than ten handbreadths high. The general principle is that the more permanent the structure, the more stringent the ruling.
Rishonim explain that the temporary canopy is not considered a fixed structure and is therefore permitted when it is less than ten handbreadths high. The two-post structure lacks a roof, so it requires the additional problem of being ten handbreadths high to become invalid. The four-post canopy has both features that create a problem: it has a roof and is a permanent structure. Therefore, even when it is less than ten handbreadths high, it is invalid.
The Gemara had quoted Rabbi Yehuda in the name of Shmuel as saying that it is permissible to sleep beneath a canopy in a sukkah. That ruling concerns a canopy less than ten handbreadths high. When it is ten handbreadths or higher, it is a separate domain, and the person is not sleeping beneath the sukkah's roofing. When it is less than ten handbreadths, it is not considered a separate domain and is permitted.
In the case of the four-post canopy, however, the issue is not merely height. Since the structure is permanent and sturdy, it is considered an enclosure even below ten handbreadths. That is why the dynamics of the four-post canopy differ from those of a sukkah above another sukkah. In the case of a sukkah beneath a sukkah, we need the upper structure to have the status of a sukkah, and a sukkah must be ten handbreadths high. In the case of the canopy, we are not trying to make it a sukkah; we are trying to determine whether it constitutes an independent enclosure. A permanent structure can have that status even when it is less than ten handbreadths high.
This concludes the discussion. When we refer to the illustrations in our study of Tractate Sukkah, we are using several books, including HaMa'or HaMevo'ar, the illustrated book on Tractate Sukkah, and a newer work called HaHod VeHaHadar. We will refer to both of those books in the audio series, as well as to Perush Hai on Tractate Sukkah.