Under established Jewish legal codes, it's forbidden to do anything to hasten death. But other teachings say its permissible to remove an "impediment" standing in the way of the natural end of life, such as a feeding tube or respirator.
Rabbis remain deeply divided over what constitutes an unreasonable obstacle to death.
Many rabbis follow a 1986 decision by Israel's chief rabbinate -- the government's highest religious authority -- that defines death as irreversible inactivity of major parts of the brain stem, which controls breathing, swallowing and other basic bodily functions.
The opinion is based on various Jewish texts including the Mishnah, an early source of rabbinical tradition, which establishes decapitation as an irrefutable sign of death. In the modern sense, the rabbis interpret a nonfunctioning brain stem as the same thing.
But others see the core of life in the heartbeat, which can occur even with a severely damaged brain stem and can continue if artificial respiration is provided.
Some rabbis cite ancient texts that say death occurs only when there is both no respiration and no "movement" in the body. They consider a heartbeat a life-signifying movement even if maintained through life-support and may counsel followers not to remove life support.
Unfortunately, one weakness to using a text as a primary source is that it can be interpretted in various ways... *sigh* "Can't win them all, can't win some of them, can't even break even." (Wikipedia and other sources)