An old Zen student called Hsiang-yen went to dokusan with Kuei-shan Ling-yu (771-853), the T'ang dynasty master, and Kuei-shan gave him a koan, of which over and over he was unable to see into it's mysteries.
Hsiang-yen decided that it was all too much for him and he would surrender. He went away and found a sacred site, the grave of the Sixth Patriarch of Chinese Zen, Hui-neng, and maintained it as a shrine. Day in and day out he had no thought about the world except his sweeping. Then one day, sweeping away, he swept a pebble into a bamboo grove beside the shrine. The pebble hit a piece of hollow bamboo and went "ping!" and he jumped up and down.
The "ping!" shook him to pieces and he said, "One ping! and I have forgotten all I knew!" and he composed a poem in his excitement: "Last year's poverty was not true poverty, this year even the wind can get through". Hsiang-yen was Enlightened (source)
Among the various types of Zen presented to the people of today there are some which are profound and some shallow, some that lead to Enlightenment and some that do not. It is said that during the time of the Buddha there were ninety or ninety-five schools of philosophy or religion in existence. Each school had its particular mode of practice, each was slightly different from the other. Since most religions have prayer in some form or another and prayer needs concentration of mind, most religions have at least a whiff of Zen. The different methods of concentration, almost limitless in number, come under the broad heading of Zen. Rather than try to specify all of them, the five main divisions of Zen as classified by Kuei-feng Tsung-mi (AKA: Keiho Shumitsu Zenji, 780-841. A Chan Master of Shenhui’s early Heze school and Fifth Ancestor of the Chinese Huayan school) whose categories are still valid and useful, will be discussed here. Outwardly these five kinds of Zen scarcely differ, however beginners need to bear in mind that in the substance and purpose of these various types there are distinct differences.
The first of these types is called bompu, or "ordinary," Zen as opposed to the other four, each of which can be thought of as a special kind of Zen suitable for the particular aims of different individuals. Bompu Zen, being free from any philosophic or religious content, is for anybody and everybody. It is a Zen practiced purely in the belief that it can improve both physical and mental health. Since it can almost certainly have no ill effects, anyone can undertake it, whatever religious beliefs he happens to hold or if he holds none at all. Bompu Zen is bound to eliminate sickness of a psychosomatic nature and to improve the health generally.
Through the practice of bompu Zen you learn to concentrate and control your mind. It never occurs to most people to try to control their minds, and unfortunately this basic training is left out of contemporary education, not being part of what is called the acquisition of knowledge. Yet without it what we learn is difficult to retain because we learn it improperly, wasting much energy in the process. Indeed, we are virtually crippled unless we know how to restrain our thoughts and concentrate our minds. Furthermore, by practicing this very excellent mode of mind training you will find yourself increasingly able to resist temptations to which you had previously succumbed, and to sever attachments which had long held you in bondage. An enrichment in personality and a strengthening of character inevitably follow since the three basic elements of mind - that is, intellect, feeling, and will - develop harmoniously. The quietist sitting practiced in Confucianism seems to have stressed mainly these effects of mind concentration. However, the fact remains that bompu Zen, although far more beneficial for the cultivation of the mind than the reading of countless books on ethics and philosophy, is unable to resolve the fundamental problem of man and his relation to the universe. Why? Because it cannot pierce the ordinary man's basic delusion of himself as distinctly other than the universe. (BACK)
The second of the five kinds of Zen is called gedo. Gedo means literally "an outside way" and so implies, from the Buddhist point of view, teachings other than Buddhist. Here we have a Zen related to religion and philosophy but yet not a Buddhist Zen. Hindu yoga, the quietist sitting of Confucianism, contemplation practices in Christianity, all these belong to the category of gedo Zen. Some examples that might meet the Gedo "outside way" criteria, that is, they are flirting with Zen --- but not embracing Buddhism in a classical or formal sense --- can be found in the works of F.M. Alexander, Franklin Merrell-Wolff, Madame H.P. Blavatsky, Alfred Pulyan and most emphatically so Pulyan's Teacher. Please note that the so-called Gedo "outside way" is NOT to be confused with Zen and "outside the Doctrine." 
Another feature of gedo Zen is that it is often practiced in order to cultivate various supranormal powers or skills, or to master certain arts beyond the reach of the ordinary man. It has been reported that some who have practiced this Zen have attained the ability to make people act without them having to say a word or move a muscle. There is something called the Emma Method which aims to accomplish such feats as walking barefooted on sharp sword blades or staring at sparrows so that they become paralyzed. All these miraculous exploits are brought about through the cultivation of Joriki the particular strength or power which comes with the strenuous practice of mind concentration. A Zen that aims exclusively at the cultivation of Joriki for such ends is NOT a Buddhist Zen. See also Joriki as well as Siddhis.
Another object for which gedo Zen is practiced is Rebirth in various heavens. Certain sects practice Zen in order to be reborn in heaven. This is NOT the object of Zen Buddhism. While the Zen Buddhist does not quarrel with the idea of various strata of heaven and the belief that one may be reborn into them through the performance of ten kinds of meritorious deeds, he himself does not crave rebirth in heaven. Conditions there are altogether too pleasant and comfortable and he can all too easily be lured from Zazen. Besides, when his merit in heaven expires he can very well land in hell. Zen Buddhists therefore believe it preferable to be born into the human world and to practice Zazen with the aim of ultimately becoming Buddha. (BACK)
The third type of Zen is shojo, literally meaning "Small Vehicle." This is the vehicle or teaching that is to take you from one state of mind (delusion) to another (Enlightenment). This small vehicle is so named because it is designed to accommodate only one's self. You can perhaps compare it to a bicycle. The large vehicle [Mahayana], on the other hand, is more like a car or bus: it takes on others as well. Hence shojo is a Zen which looks only to one's own peace of mind (see Pratyeka Buddha).
Here we have a Zen which is Buddhist but a Zen not in accord with the Buddha's highest teaching. It is rather an expedient Zen for those unable to grasp the innermost meaning of the Buddha's Enlightenment, i.e., that existence is an inseparable whole, each one of us embracing the cosmos in its totality. This being true, it follows that we cannot attain genuine peace of mind merely by seeking our own salvation while remaining indifferent to the welfare of others.
There are those, however, who simply cannot bring themselves to believe in the reality of such a world. No matter how often they are taught that the relative world of distinctions and opposites to which they cling is illusory, the product of their mistaken views, they cannot but believe otherwise. To such people the world can only seem inherently evil, full of sin and strife and suffering, of killing and being killed, and in their despair they long to escape from it. (BACK)
The fourth classification is called daijo, Great Vehicle [Mahayana] Zen, and this is a truly Buddhist Zen, for it has as its central purpose Kensho, that is, seeing into your essential nature and realizing the Way in your daily life. For those able to comprehend the import of the Buddha's own Enlightenment experience and with a desire to break through their own illusory view of the universe and experience absolute, undifferentiated Reality, the Buddha taught this mode of Zen. Buddhism is essentially a religion of Enlightenment. The Buddha after his own supreme Awakening spent some fifty years teaching people how they might themselves realize their Self-nature. His methods have been transmitted from master to disciple right down to the present day. So it can be said that a Zen which ignores or denies or belittles Enlightenment is not true daijo Buddhist Zen.
In the practice of daijo Zen your aim in the beginning is to awaken to your True-nature, but upon Enlightenment you realize that Zazen is more than a means to Enlightenment - it is the actualization of your True-nature. In this type of Zen, which has as its object Satori, it is easy to mistakenly regard Zazen as but a means. A wise teacher, however, will point out from the onset that Zazen is in fact THE actualization of the innate Buddha-nature and not merely a technique for achieving Enlightenment. If Zazen were no more than such a technique, it would follow that after Satori, Zazen would be unnecessary. But as Dogen-zenji himself pointed out, precisely the reverse is true; the more deeply you experience Satori, the more you perceive the need for practice.
The last of the five types is saijojo Zen, the highest vehicle, the culmination and crown of Buddhist Zen. This Zen was practiced by the Buddha - Shakyamuni - and is the expression of Absolute Life, life in its purest form. It is the Zazen which Dogen-zenji chiefly advocated and it involves no struggle for Satori or any other object. It is called Shikantaza.
In this highest practice, means and end coalesce. Daijo Zen and Saijojo Zen are, in point of fact, complementary. The Rinzai sect places daijo uppermost and saijojo beneath, whereas the Soto sect does the reverse. In saijojo, when rightly practiced, you sit in the firm conviction that Zazen is the actualization of your undefiled True-nature, and at the same time you sit in complete faith that the day will come when, exclaiming, "Oh, this is it!" you will unmistakably realize this True-nature. Therefore you need not self-consciously strive for Enlightenment.
Today many in the Soto sect hold that since we are all innately Buddhas, Satori is unnecessary. Such an egregious error reduces Shikantaza, which properly is the highest form of sitting, to nothing more than Bompu Zen, the first of the five types.
In addition to the Five Varieties of Zen, there are also three phases or stages of training typically found common to Zen:
- I The First Phase is shojin, the period of training in which the will and conscious effort are involved, and may take three to five years of diligent practice.
- II The Second Phase is the period of concentration without conscious effort. The disciple is at peace. He can become an assistant to the master and later become a master himself and teach others in his turn.
- III The Third Phase the spirit achieves true freedom, Enlightenment. Over and over it is found Zen historians citing the experience of full liberation being brought about by (but not limited to) hsing-chiao which consists of sending the learner traveling from one hill to another, from one school to another, studying under one master and then another.
The Japanese word for the First Phase, Shojin, translates as "ceaseless effort" or "constant effort." Said to be from the Sanskrit word "Virya" (in Pali: Viriya).(source)
- See: ZEN: Is it Buddhism?
- See as well: THE THREE PHASES OF ZEN TRAINING
- Equally as Enlightening: AS THE DAY BROKE IN ITS SPLENDOR
- And this too: ESSENTIALS OF PRACTICE AND ENLIGHTENEMENT FOR BEGINNERS
Fundamentally, our experience as experienced is not different from the Zen master's. Where
we differ is that we place a fog, a particular kind of conceptual overlay onto that experience
and then make an emotional investment in that overlay, taking it to be "real" in and of itself.
ZEN ENLIGHTENMENT IN A NUTSHELL
ON THE RAZOR'S
Source: "The Three Pillars of Zen", Kapleau, Roshi Phillip, pgs.44-52. Published by Doubleday, a division of Bantam Doubleday Dell Publishing Group. Copyright 1989 by Roshi Phillip Kapleau.