Buddha and the Six Perfections
The Buddha takes up patience as his coat of mail
And vigor as his suit of rigid armor.
The upholding of precepts is his stately steed.
And dhyana absorption is his excellent bow.
Out of his wisdom he makes up fine arrows.
Outside, he crushes the demon king's armies.
Inside, he destroys the thieves of affliction.
On account of this he is known as an Arhat.
"Dhyana," "Ch'an," "Zen." These are all precisely the same Sanskrit word (the latter two are but abbreviated transliterations of the first). Dhyana generally refers to the cultivation of the various levels of meditative absorption, from the very lowest (access concentration) up to the highest (the state of neither perception nor non-perception). But the etymological identity of these three terms should not lead us to the blind assumption that the practices associated with each are similarly identical.
Edward Conze once aptly noted that "Ch'an" represents the Chinese cultural response to Indian meditative traditions and that "Zen" represents the Japanese cultural response to Chinese Ch'an practice. What then can we say of American "Zen"? Certainly, it does serve to more or less accurately preserve a sub-species of post-monastic meditative traditions as they have recently developed in Japan. But can it justifiably claim to preserve the potent dhyana traditions of its Buddhist cultural antecedents? Helpful readings for perspective on this topic:
Traditions of Meditation in Chinese Buddhism. Edited by Peter N. Gregory. Studies in East Asian Buddhism no. 4. Honolulu: University of Hawaii Press, 1986.
The Great Calming and Contemplation. Neal Donner and Daniel B. Stevenson. Classics in East Asian Buddhism. Honolulu: University of Hawaii Press, 1993. (This is a translation and discussion of one chapter out of a very important classic work by the great T'ien T'ai Mountain monk Chih Yi [538-597 C.E.] ).
Meditating with Koans. Jonathan Christopher Cleary tr. Berkeley: Asian Humanities Press, 1992. (This is a translation of a collection of brief writings by real Ch'an practitioners put together and commented upon by Chu-hung [1535-1615 C.E.], an immensely famous Ming Dynasty Ch'an Master [a.k.a. "Lotus Pool" who also strongly advocated Pure Land practice as not antithetical to but rather supportive of Ch'an practice.)
"Arhat" here means "slayer of the thieves," the thieves in this case being those internal and external obstacles obstructing the conquest of enlightenment.