King's Vow - Ouhongan

...The original vows of the Buddhas and Bodhisattvas are established with the intention of saving all living beings, but there are two types: the original vow to purify each Buddha's land and save all living beings, and the original vow to attain Buddhahood in the impure land and save all living beings. For example, Amida's 48 vows are the former, and Shakyamuni's 500 great vows are the latter. Of the original vows of the Buddhas and Bodhisattvas, Amida's 48 vows have been well known since ancient times along with the development of Pure Land Buddhism, and the 18th vow, which says, "If all living beings sincerely believe and wish to be born in my Pure Land, and cannot save those who recite the Nembutsu just ten times, they will not become Buddhas," has been called the vow to be reborn in the Pure Land since ancient times, and is known as the royal vow because it is the most important original vow. In Pure Land Buddhism, the people whom Amida seeks to save through his original vow, namely evil people and ordinary people, are called the "real vessels of the original vow" or "true vessels of the original vow."

*Some of the terminology explanations that refer to "Royal Vows" are listed below.

Source | Heibonsha World Encyclopedia 2nd Edition | Information

…仏･菩薩の本願は生きとし生けるものの救済を本意として立てられているが，おのおのの仏国土（ぶつこくど）を浄（きよ）めて衆生を救済しようとする浄仏国土（じようぶつこくど）の本願と，現実のこの穢土（えど）で成仏して衆生を済度しようとする穢土成仏の本願とがあり，たとえば弥陀の四十八願は前者，釈迦の五百大願は後者にあたる。諸仏諸菩薩の本願のうち，弥陀の四十八願は浄土教の発展とともに古くからよく知られ，とくに〈一切の生あるものが，至心に信楽（しんぎよう）して私(弥陀のこと)の浄土に生まれようと欲し，わずか十声の念仏でも唱えた人を救済できないならば，仏とはならない〉という第十八願は古来念仏往生の願ともいわれ，最も重要な本願なので王（おう）本願と称されている。浄土教では，弥陀が本願を立てて救済しようとしている対象，すなわち悪人や凡夫を本願の実機（じつき），本願の正機などという。…

※「王本願」について言及している用語解説の一部を掲載しています。

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