Background In Jewish Law
The Four Domains
Torah Law forbids "carrying" or transfering something from a "private domain" - reshut hayachid, to a "public domain" - reshut harabim, and vice versa on Shabbat, or from carrying something a distance of four amot (plural of amah) within a reshut harabim. One can carry within a private domain (hence we can carry things within our home) or from one private domain to an adjoining private domain. As with all other malachahs, carrying is forbidden on Shabbat because it was a necessary part of building the Tabernacle during Biblical times (see Shabbat 49b). When assembling and disassembling the Tabernacle, the Levites would carry the planks that made up its walls on and off wagons - the covered wagons being a reshut haychid and the desert being a reshut harabim, and from here we derive the prohibition of "hotza'ah" - carrying (see also Shabbat 96b).
A reshut hayachid is defined as an area that is enclosed by walls (mechitzahs) that are at least ten tefachim (plural of tefach) high and encompass an area that is at least four tefachim by four tefachim1. Alternatively, a pit that is ten tefachim deep or an elevated area that is ten tefachim high would also be considered a reshut hayachid. According to Torah law, if the mechitzahs only enclose an area on three sides the area is still classified as a reshut hayachid2, although each of the three sides must be at least half made up of solid walls (omed merubeh al haparutz)3. However, the Rabbis enacted that until the area is entirely enclosed it is classified as a karmelit and one would be unable to carry into it from a reshut hayachid on Shabbat.
The definition of a reshut harabim generally follows Rambam and the Shulchan Aruch that it an open area that is at least sixteen amot wide that is accessible to the public, although Rashi (on Ervuin 6a) adds that it need also be a space in which 600,000 people travel a day - "shishim ribo"4. R Moshe Feinstein estimated that for a city, for shishim ribo to be walking the streets it would have to be multiplied five-fold, and any town or city with a populace of at least three million people living in an area measuring 12 mil by 12 mil (a mil being 2000 amot) would constitute a reshut harabim. According to most authorities, the only circumstances under which one could carry within a rehus harabim would be if the un-walled sections were filled in by delatot - doors (Mishnah Brurah: 364:2).
As a preventative measure, the rabbis in the Gemara defined two more domains in addition to the two Torah-mandated domains between which carrying was restricted (Shabbat 6a): a "karmelit" which has characteristics of both a reshut hayachid and a reshut harabim and a "makom patur" which resembles neither.
A "karmelit" is an area of at least four tefachim by four tefachim which is not enclosed in a manner that would render it a reshut hayachid. Most areas within Elstree and Borehamwood (and indeed within most eruvim) are in fact a karmelit, so to avoid confusion, the Rabbis forbade carrying between a reshut hayachid or a reshut harabim and a karmelit and vice versa5. The rabbis stipulated that a karmelit could be converted into a reshut hayachid (and hence allowed carrying within it) if any un-walled areas of the perimeter were filled with tzurat hapetachim (plural of tzurat hapetach), and it is for this reason that we use them today to make an eruv. However, for this to be effective, the area covered by the eruv must not have a reshut harabim within it since a reshut harabim cannot be converted into a reshut hayachid merely through a tzurat hapetach6.
The other category the Rabbis added is an area that is smaller than a reshut hayachid that could not be classified as a karmelit and that was called a "makom patur" - an exempt area. Carrying from or to a makom patur is allowed on Shabbat.
1 Shulchan Aruch: Aruch Chaim 345:2 2 Shulchan Aruch: Aruch Chaim 363:1 3 Shulchan Aruch: Aruch Chaim 362:9-10 4 Shulchan Aruch: Aruch Chaim 345:7 5 Shabbat 6a, see Rashi and Shulchan Aruch: Aruch Chaim 346:1; Biur Halachah: Aruch Chaim 345:7 6 Shulchan Oruch: Aruch Chaim 364:2
In times of old, cities such as Jerusalem or Jericho were encircled by walls. Apart from defending the city from invasion, such walls defined the boundaries of the city both geographical and halachically, and they established the city as a reshut hayachid. This allowed the inhabitants to carry within it on Shabbat.
The rabbis acknowledged that the walls encircling a reshut were not always intact and would need openings through which people could pass. They categorised four types of openings:
- a petach - a normal entranceway that was narrower than ten tefachim wide,
- a pirtzah - a breach that is wider than ten tefachim,
- a tzurat hapetach - a door frame made up of two vertical posts with a horizontal strip on top, and
- a lovud - a complete gap in the walls narrower than three tefachim wide which does not invalidate the eruv.
Whereas a pirtzah invalidates an eruv perimeter, a lovud does not. This means that any gaps in the fences used to demarcate the eruv perimeter must be less than three tefachim wide. Similarly, a tzurat hapetach must be no more than three tefachim away from the walls making up the rest of the perimeter.
Eruvei Chatzeirot and Shitufei Mevuot
In smaller towns and villages, houses were arranged within a walled courtyard (chatzer) that had an opening into an alleyway (movui) that serviced other courtyards. This alleyway led out into the street. To be considered a movui halachically, it had to be oblong with the entrance into the street being narrower than the depth and it had to service at least two courtyards each of which contained at least two houses. If it didn't fulfil these criteria it was classified as another courtyard. Although the courtyard and the alley were clearly a reshut hayachid, the rabbis enacted that alleyways must have some kind of landmark at their opening to the street to indicate the boundary between the reshut hayachid and the reshut harabim. This landmark could either be a vertical pole stuck to the wall of the entranceway - a lechi, or a horizontal plank going across the top of the entranceway - korah.
King Solomon decreed that one could not carry from a reshut hayachid owned by one person to that owned by another or within a reshut hayachid that bordered more than one person's dwelling (Shabbat 14b, Eruvin 21b). This meant that although technically a courtyard was a reshut hayachid, because it was owned and used communally by all of the households that it serviced within it, one could not carry from a house into that courtyard (see Eruvin 21b - compare with Rambam Hilchos Eruvin 1:4-5). However this only applied whilst people lived in the other house(s), so if the residents of only one household in a courtyard were at home for Shabbat, they could carry between their house and the courtyard (see Shulchan Aruch: Aruch Chaim 370:5). Hence the presence of others restricts their ability to carry.
To remedy this, King Solomon also enacted the laws of eruvei chatzeirot and shitufei mevuot. Eruvei chatzeirot - merging of courtyards, was a way of showing that a courtyard and the houses within it were owned by a single consortium. Since the houses and the courtyard were no longer owned by different people (or groups of people) one could carry between them. This was done by householders contributing food items - typically an item that kept well such as matzah, to a communal area within the courtyard or alleyway. A shitufei mevuot worked in much the same way, but whereas an eruv chatzeirot had to use bread (or matzah), a shitufei mevuot could use any food.