The enormous merit of this already classic book is that it can be used as a self-instruction manual on Zen. And, very specifically, on the essential condition of all Zen practice: zazen or seated meditation.

Posture, breathing, muscle tone, the mechanisms of wakefulness and attention: everything is analyzed in clear and scientific language. Also noteworthy is the examination of mental options and states of consciousness. The three types of nen or "thought impulses." The interesting parallels between Zen and Western philosophy.

The book explains, in particular, what is the purpose of zazen, the state of total stillness, samadhi where the mind is empty and, at the same time, in a state of extreme wakefulness and awareness. It is convenient to distinguish - something that Western writers do not usually do - between samadhi, or pure existence, and kensho or enlightenment. The practice of Zen does not consist, as some think, exclusively in attaining satori.

Working with koans (true catalysts of enlightenment), laughter and cognition are some of the other topics that enrich the invaluable information in this irreplaceable book.