Ascetic heresy - Kugyōgedō

...Even today, asceticism is seen as a way to be reborn in heaven, and there are many ascetics who end their lives in this way. In Buddhism, it is said that before attaining enlightenment, Shakyamuni visited ascetic sages to receive their teachings and practiced asceticism with them, and the Buddhist scriptures that explain the true life describe various hardships in a previous life, but Shakyamuni taught that one should abandon asceticism and walk the middle path, avoiding both pain and pleasure, and asceticism is called the heretical path of asceticism or the heretical path of devotion, and is counted among the heretical paths. Of course, there are records of high Buddhist monks performing ascetic acts and even destroying themselves in the process, and ascetic practices such as fasting, eating wood, and mountain seclusion performed by Shingon Buddhist monks, ascetic practices such as zazen in Zen Buddhism, and water ablutions in Shugendo are all ascetic practices in the broad sense, but since their original meaning was to purify the body and develop spirituality, they are not ascetic practices in the strict sense.

*Some of the terminology explanations that refer to "Ascetic Heresy" are listed below.

Source | Heibonsha World Encyclopedia 2nd Edition | Information

…現在でも苦行禁欲をもって天に生まれる方法となし，それによって生命を絶つ苦行者も少なくないという。仏教では釈迦が成道前に苦行の仙人のもとに行ってその教えを受け，彼らとともに苦行をしたことが仏伝にみえており，また本生（ほんじよう）を説いた経文（きようもん）には前生において種々の難行をしたことが描かれているが，釈迦は苦行をすて，苦楽の二辺をさけて中道を歩むべきことを説いており，仏教では苦行を苦行外道とか，宿作外道とか呼んで外道の中に数えている。もちろん仏教の高僧たちには苦行的な行為をなし，またこのために身をほろぼした記録があるし，真言宗の行者が行う断食，木食（もくじき），山ごもりや，禅宗の座禅のごとき苦行，あるいは修験道の水垢離（みずごり）などのごとき苦行も広義の苦行ではあるが，その元来の意味は身を浄（きよ）めて精神性を開発するものであるから，厳密な意味の苦行ではない。…

※「苦行外道」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。

出典｜株式会社平凡社世界大百科事典 第２版について | 情報