Concentration consists of all the methods taught by the Buddha for cultivating the meditative absorption called samadhi. Some traditions define the four kinds of samadhi as the samadhi of sitting, the samadhi of walking, the samadhi of sitting and walking, and the samadhi of neither sitting or walking. Essentially these four kinds of samadhi are practices of mindfulness, whether one is meditating or involved in daily life activities. In addition to the four kinds of samadhi, traditional Buddhism speaks of nine levels of samadhi attained through gradual practice, until one attains the ninth level, the samadhi of a buddha.
How is concentration practiced in Chan? There are two major methods of meditation that have evolved in Chan:
Silent Illumination, as the name implies, is the method of illuminating the mind through quiescent sitting. This practice does contain some elements of the earlier shamatha-vipashyana practice of the Theravada and is also closely related to the Zen practice of shikantaza (just sitting).
One of the great Chinese masters of this practice, Hongzhi, describes this silent sitting in this manner:
Despite the Chan hyperbole about moss and grass, Master Hongzhi's vivid description captures the intent of Silent Illumination, which is to quiet the mind so that it's innate clarity can be revealed. It is important to stress that a quiet mind does not mean that it should be blank. This illumination is active and the mind should be transparent; while it is aware of what is going on, there is no attachment or obstruction.
The method is entered by sitting in a comfortable, relaxed position (lotus or cross-legged) and putting one's entire awareness on the whole body sitting there. No attention is paid to any particulars of body or mind that come up, always returning to the awareness of "just sitting" when the mind drifts. As one continues to sit in this manner, the mind gradually settles and becomes clearer.
The stages of Silent Illumination may be described as:
In actual practice, these stages are not necessarily experienced as sequential or distinct, but one always begins with "just sitting."