Nirvāṇa is the ultimate goal of Buddhist practice, although there has been disagreement among Buddhists concerning its nature and the means of attaining it. The word derives from a Sanskrit verbal root meaning "to blow" and a prefix meaning "out." The underlying meaning of the word is traditionally explained as expressing one of two metaphors. The first is that the term means the act of blowing out or extinguishing, as of a flame. The second is that it means the act of being cooled down, as by a breeze. The two metaphors have in common the notion of fire or heat as a source of pain that is alleviated by a breeze. So the principal characteristic of nirvāṇa is relief from pain and the prevention of future pain through the eradication of its root causes. It is, in...