The four slogans of Chan or Zen are pretty much the basis of Zen although Soto Zen would argue since Dogen rejected kensho. They are as follows:
- A special transmission outside the teachings
- That does not depend upon written words
- Directly points to the human mind
- Seeing one's true nature and become Buddha.
Somewhat ironic, those new to Zen are forced to ignore the second slogan. By this I mean that those new to Zen are forced to understand Zen through written words since they are not awakened (i.e., they have not had kensho). Even for those who practice Zen at a temple or in a training monastery even they have to understand Zen through written words.
So what’s the problem with written words?
Words are inadequate to express the fundamental truth of Zen Buddhism, nor can they describe kensho which is to directly see our true nature. Short of kensho, this means that our understanding of Zen does, in fact, depend on words—and it shouldn’t. As a result, words and what they mean become the experience of Zen while kensho gets lost.
By words becoming the experience of Zen, Zen gradually gets turned into something else that isn’t Zen insofar as it doesn't transcend the five skandha of material shape, feeling, perception, volitional formations and sensory consciousness. In Western terms, the spatiotemporal world is not transcended; we are still depending upon it which keeps us in samsara.