What is the reason for the many disputes over establishing an eiruv?

In times when people lived in small villages and small towns, erecting an eiruv was much simpler than it is now. Setting up an eiruv in large cities with millions of people is far more complicated.

As mentioned in previous shiurim, the eiruv we set up nowadays, which is comprised of many tzuras hapetach, is only effective around an area that is not a biblical public domain (reshus harabim d’oraisso). Such an area must have its entrances closed with doors or gates, which is not practical.

 

What defines a reshus harabim d’oraisso?

There are two opinions in the matter. One opinion holds that an area that has streets 16 amos wide (approximately 29ft, or 9m) is a reshus harabim, while others hold that this area must also contain 600,000 people. [1] According to the stringent opinion, most of our towns and cities have streets that are 16 amos wide and thus are a reshus harabim.

However, even that is not so simple, because there are opinions who maintain that if streets curve and turn, the buildings or fences on either side form mechitzos (walls) which negate the presence of a reshus harabim. [2]

Another problem is how to define the presence of 600,000 people. What if they do not live in the given area and only pass through? What if they pass through a certain section of the town, does that render the entire town a reshus harabim?

Due to these complexities, it is not a simple matter to define whether certain areas can be surrounded with a tzuras hapesach only.

What are the other problems?

There are the acute complications in setting up a tzuras hapesach. Even if it is taken for granted that a given area is not a reshus harabim d’oraisso, the various opinions defining the halachos of a tzuras hapesach are numerous.

Due to these complications, we have conflicting opinions whether one can or should make an eiruv in large cities.

Obviously our intention is not to take sides in any matter; we are merely presenting a minute proportion of the complications involved with setting up an eiruv. One must always ask one’s rav whether it is permitted to carry within an eiruv.

Is there a limit how far one may walk on Shabbos?

Chazal said that one may not walk more than 2000 amos (approx. 1km, 0.62 miles) outside the perimeter of a town. This has nothing to do with an eiruv. This too is complicated as to how and from where to measure this distance.

Basically, a town is squared and the 2000 amos are measured from the square. [3] A large square is formed in which one may walk the entire square. This means that from the town to the corners of the square one may even walk more than 2000 amos. One may also walk more than 2000 amos within the square, provided that one does not walk outside the square or t’chum.

Is there a way to lengthen the permitted distance?

If one wishes to walk further than 2000 amos, one may do so provided that one placed an eiruv t’chumin at a certain point outside the town. This will entitle the person to walk 2000 amos in any direction from the eiruv t’chumin.

Very briefly there are two methods. One must be at a point close to the end of the original 2000 amos for the entire bein hashmashos (twilight). After nightfall one may return home and one’s starting point is now the place he was at before. As a result, one loses the 2000 amos on the opposite side of the town because the starting point is not the town, rather the point on the other side.

The other method is to place food equivalent to 18 dates, at that particular place. That point is now the starting point and the same halachos apply.

Obviously one cannot learn from these few lines and when the need arises one must thoroughly learn the halachos.

If a person in a desert does not know when it is Shabbos, how must the person conduct himself?

The main problem is that since the person does not know when it is Shabbos no melacha may be performed lest Shabbos be violated. As such, the person must deplete any provisions and subsequently melacha may be performed in order to survive, such as hunting etc. but only for that day. Additional melacha may not be performed on one day for the morrow lest that day is Shabbos.

From the time it is realized that one does not know what day it is, seven days must be counted and on the seventh kiddush is recited and havdala, in order not to forget the idea of Shabbos. On that day melachos may be performed as well in order to survive.

The person may walk as much as necessary – even more than 2000 amos – because it is vital to try and find civilization in order to survive.

Several halachos have been omitted from this shiur and one may learn them in simon 344.