The Perfect Way knows no difficulties
Except that it refuses to make preference
Only when freed from hate and love
It reveals itself fully and without disguise
A tenth of an inch's difference
And heaven and earth are set apart
If you want to see it manifest
Take no thoughts either for or against it
To set up what you like against what you dislike
That is the disease of the mind
When the deep meaning [of the way] is not understood
Peace of mind is disturbed and nothing is gained
[The Way] is perfect like unto vast space
With nothing wanting, nothing superfluous
It is indeed, do to making choices
That its suchness is lost sight of
When the mind rests supreme in the oneness of things
Dualism vanishes by itself
-beginning of the Hsin-hsin-ming by Seng-ts'an
as translated by D. T. Suzuki, Essays in Zen Buddhism, First Series
The movement we know of as Zen Buddhism is properly understood to be a contemplative sect of Mahayana Buddhism, the great vehicle of the Pure Land.
Adherents to the Zen tradition claim to be able to trace its origins to the beginning of the Buddhism, to the person of Gotama Siddhartha himself, through his disciple Ananda, to Sakyamuni.
Zen practitioners also claim that there exists an unbroken line of succession from Sakyamuni through Bodidharma to Hui-neng, the sixth and last patriarch of Zen.
Let me clarify.
What is meant by an unbroken line of succession is that the "Buddha mind," which in its essence is ineffable, and indescribable, is passed from one Buddha to the next by means of a sacred ceremony.
The transfer of enlightenment is referred to as the "transmission of the lamp;" it is the passing on of the "true dharma eye," which adherents of Buddhism claim Gotama Siddhartha possessed.
The transmission of the "true dharma eye," in Buddhism is analogous to the tradition of apostolic succession in Christianity, it is the transfer of a special charism, and a position of authority from one teacher, and one generation to the next.
However, the origins of Zen Buddhism, like the origins of the Christian Church, are shrouded in the mists of history. They are complicated by cultural traditions and politics, and there is some question regarding whether what we know of as Zen today, a predominantly Japanese form of Buddhism, developed in the Ch`an (Zen) school of Chinese Buddhism, derived from the Buddhism brought from India into China by the missionary monk Bodidharma (c. 520 CE), or whether it is derived from the practice of quietism that was developed by a near contemporary of the original Buddha, Lao Tzu (c.500 BCE), whose teachings became the foundation for the Chinese religion Taoism.
Whatever the origins of Zen Buddhism may have been, what constitutes Zen today is the physical and mental, and spiritual discipline, which its practitioners claim is a genuine and inspired route to enlightenment.
The great teacher, D. T. Suzuki says in his elegant treatise on The Training of a Zen Buddhist Monk, says:
As Zen is a discipline and not a philosophy, it deals directly with life; and this is where Zen has developed its most characteristic features. It may be described as a form of mysticism, but the way it handles its experience is altogether unique. Hence the special designation of Zen Buddhism.[i]
The practitioner of Zen, may appear to an outside observer as someone engaged in a mystical exercise, but from the practitioners perspective they are engaged in the art of living.