"It is customary among physicians to name anyone who departs from the basic practices of medicine a “practitioner of outside ways.” In human society one speaks of those relatives who are of a surname other than one’s own as “outside relatives.” And in Buddhism, that which departs from the sutras and treatises is known as an “outside way.”
The Nirvana Sutra states, “If there is any person who does not abide by the expositions of the Buddha, you should understand that this person is a servant of the devil.” And volume nine of On “Great Concentration and Insight” says, “Before the Lotus Sutra, they were disciples of an outside [non-Buddhist] way.”
The Zen school describes itself as something “not transmitted by the Buddha and patriarchs.” [What is your opinion on this?]
Answer: If that is so, then why does the Zen school talk about the “twenty-eight patriarchs of India” and the “six patriarchs of China”? If you speak in this way, you are refuting your own assertion that the teachings were entrusted to Mahākāshyapa, are you not? How do you explain this contradiction in your own words?
The Zen school says, “This superior way of ours has not been transmitted by the sages of the past.”
Answer: If that is so, then the Zen school of today can have no real understanding of this “superior way” either. And if it has no real understanding of it, then it is not true Zen!
All the Zen school does is sing about a “superior way,” resting in arrogance, never correcting its deluded views but instead boasting of “perceiving one’s true nature.” Its greatest mistake is to create gaps between people’s capacities and the Buddha’s teachings. In doing so, it impedes the enlightening process of the Buddha’s teachings and falls ever deeper into error.
The Zen followers talk about a doctrine “outside the sutras” and practice this thing “outside the sutras”; they say their doctrine is “independent of words or writing,” yet they love to take up their brushes and write about it. Their words and their hearts fail to match—how could they be other than followers of the heavenly devil, disciples of a non-Buddhist way?
It is through the use of words and letters that the Buddha saves living beings."