Generally speaking, Son (in Korean) meditation, is a discipline to attain freedom of the mind by becoming enlightened to one's own Nature, which originally bears no discrimination or attachment. Whoever has had an ambition to attain the great Way has practiced Son meditation.
If one intends to practice Son correctly, one should first of all consider the Absolute Void as the fundamental, and Abstruse Beings as functional so that outwardly one can behave as firmly as a huge mountain when confronting numerous trying situations, while inwardly keeping one's mind as pure as the Void. Try to use the mind without moving it when in motion and without resting it when still. if one is able to do this, all thoughts will not leave Samadhi and the functioning of the Six Roots will coincide with the Original Nature of Divine Wisdom in the Void. This is called Mahayana meditation, and is the method of practicing the Threefold Learnings together.
Thus it is written in the Diamond Sutra, 'Use your mind without abiding in any of the things to which you respond'. This is the great way to cultivate oneself so that in all kinds of disturbing situations one remains unmoved. This seems very difficult to practice, but after mastering its method, Son can be easily practiced by a farmer holding a hoe, a mechanic holding a hammer, a clerk holding an abacus or by an official in charge of an administrative business. One can practice Son while coming and going or while at home. Why does one have to look for a place to meditate or argue the need for quietness in order to meditate?
One who is just beginning the practice of meditation, however, cannot control one's mind as desired. This is similar to taming a cow in that when one slackens the reins of the mind for even a moment, the moral sense is immediately destroyed. Hence, one should not lose the spirit to fight against trying situations that arouse avarice in one's mind, but one should strive to cultivate the ability of the mind to concentrate. Gradually, the mind will mature so that one can reach a state where one can control one's own mind as one wishes. Whenever one meets a trying situation, one should remind oneself that it is an opportunity to train the mind and one should only check whether the mind is drawn to the situation. If one feels that the function of one's mind is usually under control, one may put one's mind in a situation which one usually likes very much, or in a situation which one abhors. If one's mind is still drawn or moved, it is because one's moral sense is immature; if the mind is not drawn or moved, one' may take it as a sign that one's moral sense is becoming mature. However, one should not be put off guard immediately if it is found that the mind is not moved. One's mind is not moved, not because the mind is immune to trying situations, but because the mind is under control; the mind is well-tamed if it is not moved even when it is not under control.
If, because of a long continual meditation one attains freedom of the mind by cutting off all worldly desires, one will have attained a subjectivity as unmovable as a steel pillar and as impenetrable as a granite wall, and the mind will not be tempted by wealth or honor and will not yield to a sword or to worldly power. With this sort of mind, one can do everything without being entangled in, or blocked by, anything, and even in this mundane world, one can always attain a hundred thousand Samadhi. If one reaches this stage, the whole world will become a true Dharma world where all right and wrong, good and evil, impure and pure will provide one with a most dainty taste of Jaeho (a rich liquor skimmed from boiled butter). This state is called the Gate of Undivided Truth, from which emerges freedom from birth and death, emancipation from the cycle of the Six Paths, and from which also emerges the Absolute Bliss of the Pure Land.
Recently, some groups of people who practice meditation think that meditation is very difficult and they have given the opinion that, in order to meditate, one must enter a remote mountain region and sit calmly so as not to be disturbed by one's family or by one's occupation. This is because they do not know the great principle that all things are one. If one can meditate only when one is sitting, but cannot meditate when one is standing, then one's meditation is a sickly meditation. How can this be the great Way to deliver the world? Moreover, one's Nature, itself, is not exclusively a void, so that if one practices meditation like a lifeless log, it is not a meditation that will train one's Nature but rather a useless meditation which only paralyzes the person who is meditating. Hence real Son will be such that in a disturbing situation one's mind will not be disturbed, and in a situation which arouses avarice, one's mind will not be moved.
The main principle of continual meditation is as follows: "When the Six Roots are free from work, exclude worldly thoughts from one's mind and cultivate the mind's ability to concentrate, and when the Six Roots are at work, exclude what is unrighteous and cultivate what is righteous."