Zen (禅; Chinese chán; "meditation") is a school of Mahayana Buddhism originating in China as a distinct school, though it had some background in India and claimed to be derived from the enlightenment-experience of Sakyamuni and transmitted to Bodhidharma, considered to be the founder of Zen in China, probably in the early 5th century A.D. Zen, as a Chinese product, emerged in the teachings of Hui-neng around 675. Zen masters claim that conceptual knowledge, including religious texts, will not lead to a direct experience of one's own True Nature. D.T. Suzuki, an exponent of Zen writes that Zen is universal and is "being life itself". Suzuki explains: "When I say that Zen is life, I mean that zen is not to be confined within conceptualization, that Zen is what makes conceptualization possible, and therefore that Zen is not to be identified with any particular brand of 'ism.'" [1]
Zen is not a philosophy in the traditional Western sense where intellectual understanding is a goal. Life is found in the living. To know is to do.
The koan (公案; Chinese gōng'àn; lit., "public [law] case," but also "mysterious case") is a kind of poem. It is not, say Zen adherents, something that can be examined or analyzed. Zen teachers frequently employ the koan, a kind of question which admits of no immediate rational answer, as a teaching tool to bring about a "Satori" without which there is no Zen. For example one koan states "The sound of one hand clapping." While this may sound paradoxical to a rational mind, it is very obvious to anyone who has done that.
Zen is not a doctrine to be grasped but if you try anyway, Masters say that it is not this, it is not that. Enlightenment is the central teaching of Zen which does not come from a book or revelation. For example, one koan goes like this - "Do not mistake the pointing finger for the moon." Our concepts are but pointing fingers and are dualistic in that there is that which is pointed at and there is that which is not pointed at. This distinction implies a separation which in turn suggests a difference. But this difference comes from the self. It is self-imposed on us. Enlightenment then is not gaining of a secret/supreme knowledge, enlightenment is knowledge that the "self" had duped itself into thinking it was all there is. Enlightenment is KNOWING for the first time that we really didn't know what we were thinking/talking about in the first place.
Proponents of almost every school claim that there is a Self, notice the capitalization, and a small self. It is the small self, our ego, they tell us, which views reality (Maya) through the mind. Self, as in whole Self, is the ground or whole Self. Outwardly we experience ourselves as separate from the rest of all of it. While inwardly, we are all the whole where no distinction can be made between this and that. The Roman Poet Lucretius , said, "and where there is no distinction, there is no difference,"
Ultimately, on the words of Ken Wilber, "The purpose of an integral/life/practice is to realize the full spectrum of your unique and special capacities." (p. 160)[2]
Because Zen is action, several methodologies are employed in order to bring about a Satori and subsequent "enlightenment." One of those techniques is meditation or "Zazen" (坐禅; Chinese zuòchán; "sitting meditation"). Here the goal is to take control of the mind with the eventual goal of leaving the mind behind much like one leaves a boat behind after crossing the stream.
Perhaps more importantly, because Zen is freedom from the constraints of the mind, proper thought and action must come first. It can be dangerous to achieve Selfhood if one is encumbered with "bad habits" which are not consistent with those of the greater Self.