Personal experience is everything in Zen. No ideas are intelligible to those who have no backing of experience. This is a platitude. A baby has no ideas, for its mentality is not yet so developed as to experience anything in the way of ideas. If It has them at all, they must be something extremely obscure and blurred and not in correspondence with realities.
To get the clearest and most efficient understanding of a thing, therefore, it must be experienced personally. Especially when the thing is concerned with life itself, personal experience is an absolute necessity. Without this experience nothing relative to its profound working will ever be accurately and therefore efficiently grasped. The foundation of all concepts is simple, unsophisticated experience. Zen places the utmost emphasis upon this foundation experience, and it is around this that Zen constructs all the verbal and conceptual scaffold which is found in its literature known as “Sayings”. Though the scaffold affords a most useful means to reach the inmost reality, it is still an elaboration and artificiality. We lose its whole significance when it is taken for a final reality.
The nature of the human understanding compels us not to put too much confidence in the superstructure. Mystification is far from being the object of Zen itself, but to hose who have not touched the central fact of life, Zen inevitably appears a mystifying. Penetrate through the conceptual superstructure and what is imagined to be a mystification will at once disappear and at the same time there will be enlightenment known as “satori”.
Zen, therefore, most strongly and persistently insists on an inner spiritual experience. It does not attach any Intrinsic importance to the sacred sutras or to their exegeses by the wise and learned. Personal experience is strongly set against authority and objective revelation and as the most practical method of attaining spiritual enlightenment the followers of Zen propose the practice of Dhyana. Known as Zazen in Japanese.
A few words must be said here in regard to the systematic training by Zen of its followers in the attainment of the spiritual insight which has been referred to before as the foundation experience of Zen. For this is where Zen pre-eminently distinguishes itself from other forms of mysticism. To most mystics such spiritual experience, so intensely personal, comes as something sporadic, isolated and unexpected. Christians use prayer, or mortification or contemplation so called, as the means of bringing this on themselves and leave its fulfillment to divine grace. But as Buddhism does not recognize a supernatural agency in such matters, the Zen method of spiritual training is practical and systematic.
From the beginning of its history in China there has been such a tendency well marked; but, as time went on, a regular system has finally come into existence, and the Zen school at present has a thoroughgoing method for its followers to train themselves in the attainment of their object. Herein lies the practical merit of Zen. While it is highly speculative on the one hand, its methodical disciple on the other hand produces most fruitful and beneficial results on moral character when it is expressed in connection with the facts of our everyday practical life, but here it is where we have to appreciate the real value of Zen, for Zen finds an inexpressibly deep thought even in holding up a finger, or in saying a “good morning” to a friend casually met on the street, In the eye of Zen the most practical is the most abstruse and vice versa. All the system of discipline adopted by Zen is the outcome of this fundamental experience.
[ Excerpts from "An Introduction to Zen Buddhism" published in 1964]