Buddhist and non-Buddhist religions, lay stress on scriptural authority,
that is holy books, writings, and doctrine. But Zen denounces all this
on the grounds that words or characters can never adequately express
religious truth, which can only be realized from within. Consequently
Zen claims that the Enlightenment of Buddha has been handed down neither
by word of mouth, nor by the letters of scriptures, but from teacher's
heart to disciple's heart, through a line of personal transmission until
the present day. Zen is an isolated instance of this heart-to-heart
transmission in the whole history of the worlds religions. by Kaiten
Nukariya, The Religion of the Samurai.