The Melacha of Hotza'ah: Carrying Between Domains on Shabbos
Hotza'ah includes transferring an object from one halachic domain to another and carrying it within a reshus harabim. It is one of the thirty-nine melachos of Shabbos.
The four halachic domains
The halachos of Shabbos distinguish a reshus hayachid, reshus harabim, karmelis, and makom petur. Their definitions determine whether moving an object is forbidden min haTorah, forbidden mid'Rabbanan, or permitted.
Everyday ownership does not decide the halachic status. A privately owned passage can have the status of a public domain, while an enclosed area used by many people can be a reshus hayachid.
The classification of the place determines which acts are forbidden min haTorah and which are forbidden mid'Rabbanan. It also determines what kind of enclosure would be required before carrying could be permitted.
Transferring between domains
Taking an object from a building into the street, or bringing it from the street inside, can be hotza'ah even when the distance is very short. The act includes uprooting the object in one domain, carrying it, and placing it in the other.
A threshold, vestibule, set of steps, fenced yard, sidewalk, and street may have different halachic statuses. Setting an object down along the way, passing it to another person, or dividing the route does not create an ordinary permission and can introduce additional prohibitions.
Carrying four amos
Carrying an object four amos within a reshus harabim is a separate form of hotza'ah. A person can therefore violate the melacha without crossing from a building into the street.
Four amos is a halachic measure, not a rough count of four ordinary steps. Repeatedly stopping or putting an object down is not a practical way to carry it through the neighborhood.
What a valid eruv changes
A valid halachic enclosure can make the enclosed area a reshus hayachid for carrying, subject to the communal arrangements required by Chazal. It does not remove the melacha itself, and an enclosure that is invalid or broken cannot be relied upon.
The physical boundary, the status of the streets, eruv chatzeiros or shitufei mevo'os, sechiras reshus where required, and continuing inspection are related parts of one halachic arrangement. A wire alone is not the eruv.