It does not have a central sutra because of the principle of furyumonji (the thought that the status of enlightenment cannot be expressed in characters or discourses) and emphasizes shishi sosho (transmission of the teachings and the way of Buddhism from a teacher to a disciple) because of the principle of transmission of spiritual awakening without words or characters and in a heart-to-heart way.
不立文字を原則とするため中心的経典を立てず、教外別伝を原則とするため師資相承を重視する。