To facilitate insight, a Zen teacher can assign a kōan. This is a short anecdote, which seems irrational, but contains subtle references to the Buddhist teachings. An example of a kōan is Joshu's 'Mu': "A monk asked: "Does a dog have buddha-nature?" Joshu responded: "Mu!"" Zen-meditation aims at "non-thinking," in Japanese "fu shiryō" and "hi shiryō". According to Zhu, the two terms negate two different cognitive functions both called "manas" in Yogacara, namely "intentionality" or self-centered thinking, and "discriminative thinking" ("vikalpa"). The usage of two different terms for "non-thinking" points to a crucial difference between Sōtō and Rinzai in their interpretation of the negation of these two cognitive functions. According to Rui, Rinzai Zen starts with "hi shiryō", negating discriminative thinking, and culminates in "fu shiryō", negating intentional or self-centered thinking; Sōtō starts with "fu shiryō", which is displaced and absorbed by "hi shiryō". The traditional institutional traditions ("su") of Zen in contemporary Japan are Sōtō (), Rinzai (), and Ōbaku (). Sōtō and Rinzai dominate, while Ōbaku is smaller. Besides these there are modern Zen organizations which have especially attracted Western lay followers, namely the Sanbo Kyodan and the FAS Society. Sōtō emphasizes meditation and the inseparable nature of practice and insight. Its founder Dogen is still highly revered. Soto is characterized by its flexibility and openness. No commitment to study is expected and practice can be resumed voluntarily. Rinzai emphasizes kōan study and kensho. The Rinzai organisation includes fifteen subschools based on temple affiliation. The best known of these main temples are Myoshin-ji, Nanzen-ji, Tenryū-ji, Daitoku-ji, and Tofuku-ji. Rinzai is characterized by its stringent regiments of meditation through every second of life. Whether a practitioner is practicing seated meditation, walking meditation, working, or even out in public, meditation can be applied to each instance of a Rinzai student's life. Ōbaku is a small branch, which organizationally, is part of the Rinzai school. The Sanbo Kyodan is a small Japanese school, established by Hakuun Yasutani, which has been very influential in the West.