The social order was disrupted as a result of these conflicts, with changes to society in general and, naturally, shifts in literary styles and tastes. The philosophy of impermanence (無常 "mujō") became pervasive, with many seeking salvation, both physical and spiritual, in religion, specifically Buddhism. The basic ideal that informed aesthetic tastes in this period is known as "yūgen" (roughly meaning "mystery" or "depth"), along with other concepts such as "ushin" (有心, literally "possessing heart", the more "weighty" or "serious" poetry, as opposed to games) and "yōen" (妖艶, literally "ethereal beauty"). These ideals shunned realism, representing a spirit of "l'art pour l'art" and aiming to plunge the reader into an "ideal" world, and were in accord with the ideals of Buddhist monastic seclusion (出家遁世 "shukke-tonsei"). What exactly constituted "yūgen" differed throughout its history, and the various literary genres it influenced include "waka" ("Japanese poetry", meaning poetry in vernacular Japanese, typically in a 5-7-5-7-7 metre), "renga" ("linked verse") and the "noh" theatre. Later developments include "en" (艶, literally "lustre" or "polish"), "hie" (ひえ) and "sabi" (roughly "stillness" or "attenuation"), connecting to the literature of Japan's early modern period. Translator and literary historian Donald Keene discusses both "yūgen" and "hie" (which he translated "chill") as concepts shared by the quintessentially medieval art forms of "renga" and "noh". He describes "sabi" as having been "used to suggest the unobtrusive, unassertive beauty that was the ideal of Japanese poets, especially during the turbulent decades of the Japanese middle ages", and states that it first came to prominence around the time of the "Shin-kokin Wakashū". There was, however, a concurrent trend toward a form of realism in medieval developments on the concept of "okashi" (をかし; "bright", "happy", "charming", "humorous" or "brilliant"). Authors began to attempt to reflect reality in order satirize social conditions, or for simple enjoyment.