We have seen that, in the ancient layout of cities, courtyards and alleys could be made into Private Domains by means of the Eruiv, but that Public Domains probably could not, unless first made into semi-Public Domains (Karmelit) by means of barriers at each end. What about our modern cities?
It would appear, at first glance, that most of our city streets cannot have an Eruv. The definition of a Public Domain derives from the thoroughfare between the encampments in the wilderness. The only stipulations that we find in the Talmud are that they extend from one end of the city (or encampment) to the other, unobstructed, and that they be sixteen cubits (about twenty four feet or about seven and a half meters) wide. That would make just about any city street into a Public Domain! A minority view of a Ninth Century rabbi was picked up and accepted two centuries later by Rashi, This view says that in the wilderness, the population was six hundred thousand. Therefore, any street would have to have that number of people walking on it daily to qualify as a Public Domain; otherwise it remains a Karmelit. Some cities do indeed have that number or people. In my native New York City, there are many; thus, theoretically, rendering an eruv impossible. Other parts of the city would be able to make an Eruv. Smaller cities would not be likely to have such a situation at all. There were, and are, many who disagree with Rashi. There is no hint of the six hundred thousand people idea in the Talmudic sources of Eruv. If we will add that, why not other features of the wilderness situation? Perhaps we need the Sanctuary in the Middle? Perhaps we need Moses and Aaron? These rabbis rejected totally the ability to make an eruv in a modern city, Most Ashkenazi rabbis did accept Rashi's view, mostly because of the stature of Rashi. In fact, one would be hard pressed to find a yeshiva student who would not immediately blurt out, if asked the definition of a Public Domain, the number six hundred thousand. Most Sepharadim rejected this view. However, this had little effect in the past, as most Mediterranean cities maintained the ancient structure of courtyards well into modern times. In the Shulchan Aruch, Rabbi Yosef Karo mentions the idea of six hundred thousand as "some say". while the Ashkenazic view, Rabbi Moshe Isserles, quotes it as being the accepted position.
Another issue is the question of the enclosure. Any area where an eruv is to be made must be enclosed. Although some require an actual wall or fence, an enclosure consisting of a wire or string, held up on poles, was considered acceptable by most. But many felt that although this would be acceptable in a place requiring an Eruv only by rabbinical law, this would not hold true for a Biblical Public Domain. Many rabbis do not consider city Eruvin "kosher" for this reason especially.
A very novel approach was taken by the twentieth century rabbi, Rabbi A. Y. Kerelitz, known as Chazon Ish. He opined that the way our streets are set up, with houses and other buildings lining our thoroughfares, is in and of itself walls. Although they have large gaps, rendering them invalid by Rabbinic Law, they would be good by Biblical law, rendering then Karmelit, which could then be easily made into Private Domains by the usual Eruv procedures. This view has been widely accepted. Therefore, the vast majority of rabbis, both Ashkenazi and Sepharadi, do accept the possibility of making an Eruv in modern cities. (There are notable exceptions to this in both communities).
But is Eruv making desirable? What do we gain and what do we lose? That will be my next post.