The Laws of Lo Plug
When Chazal institute takonos (enactments) or gezeiros (Rabbinic decrees), they use the principle of lo plug (“we make no distinction”), grouping all possible situations under a single model, without considering case-by-case psak (ruling). This form of “unified” halachah bolsters the acceptance of the gezeirah by all individuals. “If we permit certain unique circumstances,” they reason, “people will extend that to other situations …” until the whole fabric of the particular gezeirah unravels.
The takanah of Chazaras Hashatz (the repetition of the chazzan—prayer leader—of the Amidah prayer) follows this principle. It was established across the board at a juncture when it was assumed that a good number of those attending the minyan (prayer quorum) were illiterate and incapable of davening on their own. They could thus be yotzei (fulfill their obligation) davening by responding to the chazzan’s repetition of the Amidah. Whether a particular minyan is/was completely literate, and whether statistically speaking literacy is on the upswing in a particular generation is irrelevant—we continue this practice due to lo plug.
The subject of lo plug engenders much controversial discussion among poskim, and has many parameters. One general rule of lo plug determines issur or heter (restriction or permissibility) based on the majority of cases relating to a particular topic. So in some instances, according to the principle of lo plug, a unified heter is issued, despite particular cases that would normally be prohibited.
There are halachic decisions in certain cases that do not follow the model of lo plug, owing to factors which are clearly distinct (which would therefore deter people from muddling them), or the particular language of the decree is considered specific enough to clearly define what is included and what is not.
Examples of gezeiros that do not follow the principle of lo plug are: putting raw meat on the fire to cook before Shabbos to the exclusion of all other raw food, and using liquids that were left uncovered overnight in locales where snakes are not prevalent (see Halachah #168 and Halachah #568 for details).