Is flipping a light switch on the Sabbath like lighting a fire?
Ancient Jewish law says nothing about electricity, so rabbis had to reason by analogy. Many Orthodox authorities compare closing a circuit to kindling fire, since it can make a spark, and forbid it on the Sabbath. Conservative authorities liken it instead to opening a water tap, which is allowed, and permit it.
That split shows how halakha, the body of Jewish religious law, actually works. The word comes from a Hebrew root meaning to walk, so a closer translation than law is something like the way to go. It covers far more than ritual, reaching into business dealings, food, family life and daily conduct, and it stands beside aggadah, the storytelling and philosophical side of rabbinic writing, with the two borrowing from each other.
Its foundation is the tally of 613 commandments the Talmud finds in the Torah: 248 instructions to do something and 365 prohibitions. Many depend on the Temple in Jerusalem, so by one count only 369 can be kept today. Some rules have obvious social purposes. Others, called chukim, come with no stated reason, such as the ban on wearing cloth that mixes wool and linen. Layered on top are rabbinic decrees meant to fence off violations, new regulations, local customs and centuries of written questions and answers known as responsa.
What halakha lacks is a supreme court. The Sanhedrin once issued binding rulings for all Jews, but it stopped functioning fully in 40 CE, and no body since has been accepted as able to set universal precedent. Instead, a decisor called a posek answers a question for the person asking and their community. If the reasoning is persuasive and the posek respected, other rabbis gradually adopt it, a kind of informal peer review. That is why communities long separated from each other, including Ashkenazi, Sephardi, Yemenite and Ethiopian Jews, differ on smaller points.
Two pressures pull against each other. One principle discourages overturning an earlier accepted ruling without older precedent; another gives weight to the judgement of the authority facing a new situation now. A further rule, known in Aramaic as dina d'malchuta dina, the law of the kingdom is law, has long told Jews living under other governments to follow local civil and commercial law, so long as it does not contradict Jewish law.
Source: Halakha
