Zazen, the practice of seated (za 坐) meditation (zen 禅), has attracted much attention recently for its many beneficial effects on physical health (lowered blood pressure and heart rate, enhanced immune function, etc.), on mental function (increased creativity and focus, etc.) and on emotional well-being (decreased stress and anxiety, enhanced sense of empathy and compassion, etc.). Important as these benefits are, however, they are relatively superficial compared to the spiritual goal toward which meditation has traditionally been directed.
This goal is expressed in Zen in several different ways: the investigation and clarification of the self, the resolution of the question of birth and death, and (borrowing from the Lotus Sutra) the realization of the One Great Matter of Buddhism (that is, to experience the same enlightenment as the Buddha and help other beings to do the same). Zazen is the means by which these are attained, and the heart of the spiritual path as taught by Shakyamuni Buddha.
The fact that the word zazen means “seated meditation” does not mean that it is limited to the sitting posture. Huineng, the Sixth Patriarch, described seated zazen as follows:
Externally, to be free of all hindrances and undisturbed in mind regarding any circumstances whether good or bad is called “sitting” (za); internally, to contemplate the immutability of your own Original Nature is called “meditation” (zen).
Zazen in this sense is possible regardless of what one is doing, and in fact Zen training is ultimately about learning to maintain the meditative mind—the mind of zazen—throughout all of one’s daily activities. Nevertheless, the seated posture, which facilitates the ideal combination of relaxation and alertness, is the easiest posture in which to practice and deepen the meditative state. It most readily enables the body to be still and relaxed and the mind to be tranquil and settled. The state of zazen is one of union of body and mind attained through the regulation of the breath and the relaxed, open contemplation of our original nature free of discriminative thoughts.