There are many ways of entering into enlightenment, but all of them may effectively be subsumed under two categories: the "entrance of principle" and the "entrance of practice".
The entrance of principle is to become enlightened to the Truth on the basis of the teaching. One must have a profound faith in the fact that one and the same True Nature is possessed of all sentient beings, both ordinary and enlightened, and that this True Nature is only covered up and made imperceptible by false sense impressions.
If one discards the false and takes refuge in the True, one resides frozen in "wall contemplation", in which self and other, ordinary person and sage, are one and the same; one resides fixedly without wavering, never again to be swayed by written teachings. To be thus mysteriously identified with the True Principle, to be without discrimination, serene and inactive: This is called the entrance of principle.
The entrance of practice refers to the "four practices" which encompass all other practices. They are the "practice of retribution of enmity," the "practice of acceptance of circumstances," the "practice of the absence of craving," and the "practice of accordance with the Dharma."
What is the practice of the retribution of enmity? When the practitioner of Buddhist spiritual training experiences suffering, he should think to himself:
"For innumerable eons I have wandered through the various states of existence, forsaking the fundamental for the derivative, generating a great deal of enmity and distaste and bringing an unlimited amount of injury and discord upon others. My present suffering constitutes the fruition of my past crimes and karma, rather than anything bequeathed to me from any heavenly or human being. I shall accept it patiently and contentedly, without complaint."
When you react to events in this fashion, you can be in accord with Principle, therefore this is called practice of the retribution of enmity.
The second is the practice of the acceptance of circumstances. Sentient beings have no unchanging self and are entirely subject to the impact of their circumstances. Whether one experiences suffering or pleasure, both are generated from one’s circumstances. If one experiences fame, fortune, and other forms of superior karmic retribution, this is the result of past causes.
Although one may experience good fortune now, when the circumstances responsible for its present manifestation are exhausted, it will disappear. How could one take joy in good fortune? Since success and failure depend on circumstances, the mind should remain unchanged. It should be unmoved even by the winds of good fortune, but mysteriously in accordance with the Tao. Therefore, this is called the practice of acceptance of circumstances.
The third is the practice of the absence of craving. The various kinds of covetousness and attachment that people experience in their never-ending ignorance are referred to as craving. The wise person is enlightened to the Truth, the essential principle which is contrary to human convention. He pacifies his mind in inactivity and accepts whatever happens to him. Understanding that all existence is nonsubstantial, he is without desire. The sutra says: "To have craving entails suffering; to be without craving means joy." Understand clearly that to be without craving is equivalent to the true practice of the Path.
The fourth is the practice of accordance with the Dharma. The absolute principle of essential purity is called Dharma. According to this principle, all characteristics are nonsubstantial and there is no defilement and no attachment, no "this" and "that." Since this Dharma is without parsimony, one should practice the perfection of dana (selfless giving), giving of one’s body, life, and possessions without any regret. In this way one benefits self as well as othersornamenting the path of enlightenment.
The crux of the entrance of principle is of course the troublesome term “wall contemplation.” This term is without precedent in prior texts and is subject to a number of interpretations by later Chinese authorities.
In the preface to the work T’an-lin refers to the teaching of “pacification of the mind,” which is one of the most common terms for spiritual endeavor and meditation practice in early Ch’an. Tsung-mi refers to wall contemplation as an allegory for Bodhidharma’s unverbalized teaching of mind and its essence of "knowing." Huang-po His-yun refers to the practice of physically facing a wall in meditation. One text states that Bodhidharma “always sat in silence facing the wall, so people called him the ‘wall-contemplating Brahmin.’”
Modern interpretations have been diverse: “pacification of the mind in which the mind is mysteriously united with tranquility;” “mind is like a wall forgetting words and concepts.” Professor Yanagida offers the controversial, “...pikuan means ‘the wall contemplates,’ not ‘one contemplates a wall.’ One becomes a wall and contemplates as such.”
In general, the caves at Yun-kang and Lung-men that were created from the Northern Wei onward had countless numbers of buddhas and bodhisattvas carved into all four walls. The eyes of the buddhas and boddhisattvas were also carved into the floors and ceilings. These stone images witnessed the history of the people that entered and left such caves.
When Bodhidharma first arrived, he presumably sat alone in meditation in such a cave. His was not a practice of “facing a wall,” but of becoming a wall and witnessing himself and the world. He saw the emptiness of history, he saw the truth of the identity of unenlightened person and sage. I believe that this was the origin of the word “wall contemplation.”
At the same time “wall contemplation” includes the idea of “turning back the brilliance in counterillumination, the wonderfully bright radiance of the setting sun. Or the inconceivable function of the mirror which illuminates each and every thing in existence…