Lit. "profound mystery." A multivalent and influential medieval aesthetic ideal expressing darkness, depth, mystery, transience, ambiguity, calm, sadness, and elegance.
The term originated in China as youxuan and meant Daoist or Buddhist truth beyond intellectual comprehension. In the Chinese preface to the Kokinshū 古今集, Ki no Yoshimochi 紀淑望 (d. 919) used yūgen to denote profundity in ancient poetry. By the 12th century yūgen was used as a critical term in poetry contests (see *uta-awase-e 歌合絵), again referring to a profound meaning. Fujiwara Shunzei 藤原俊成 (1114-1204), however, considerably broadened yūgen to embrace the complete effect of a poem, including both style and concept. Shunzei integrated yūgen with aspects of yojō 余情 or overtones, evoking associations not overtly expressed in word or form, that reflect a subtleness of thought and emotion. Yūgen is also linked to the Tendai 天台 Buddhist idea of shikan 止観 which paradoxically interrelates form and formlessness, surface and depth, suggesting the interpenetration of all things.
Shunzei's son, Fujiwara Teika 藤原定家 (1162-1241) generally subscribed to this ideal, but added an aspect of yōen 妖艶 or ethereal charm that held great appeal in later generations. Kamo no Chōmei 鴨長明 (1155-1216) emphasized yūgen as an uncertainty of heart and words expressed in that which is colorless, indistinct, and emotionally restrained. For later writers such as Yoshida Kenkō 吉田兼好 (1283-1350) and Shōtetsu 正徹 (1381-1459), yūgen was a feeling that could not be put into words, a stifling of chromatic intensity, and an elegant emotion. Chōmei's yūgen, with its emphasis on the incomplete, the old, and the faded, saw an evolution in the surface appeal of the term but weakened its intellectual or spiritual element.
The *Noh 能 dramatist and theoretician Zeami 世阿弥 (1363-1443) applied yūgen to the sublime level of acting that expressed a vivid yet tranquil beauty, describing the term metaphorically as a white bird that holds a flower in its beak. The renga 連歌 master Shinkei 心敬 (1406-75) reemphasized the spiritual essence of yūgen, associating the creation of elegantly beautiful poetry with a pure state of mind born of Buddhist acceptance of the world. Shinkei's austere conception of yūgen, linked with hiesabi ひえさび (chill melancholy) was further refined in the stark, withered beauty advocated by the Noh dramatist Konparu Zenchiku 金春禅竹 (1405-68). Yūgen played a formative role in the aesthetic ideals of *sabi さび and *wabi わび and was thus expressed indirectly in the whole range of arts associated with *chanoyu 茶湯 as manifest in wabicha わび茶. The conception of beauty derived from the imperfect aspect of nature that could suggest spiritual depth below the surface is the ideological essence of wabi. Moreover, Shinkei's yūgen or a specifically "withered" and "cold" beauty, seems to have directly influenced the early developers of wabicha, Murata Jukō (d. 1502) 村田珠光 and Takeno Jōō 武野紹鴎 (1502-55). Yūgen was brought to bear directly on tea in the mid-17th century *kireisabi 綺麗さび aesthetic of Kobori Enshū 小堀遠州 (1579-1647) who took Teika as his model. Even the name "Tan'yū" 探幽 given to the Kano 狩野 artist previously called Morinobu 守信 (1602-74) by the Daitokuji 大徳寺 priest Kōgetsu Sōgan 江月宗玩 (1570-1643) is likely related to the taste for yūgen as both men studied tea under Enshū.