the mind has the same nature as space (akasa/aether), it is the same as the heart and because space has the same nature as the mind, it is the same as bodhi. In this way, oh master of mysteries, the mind, the space and the bodhi, these three are the same. The root of these is compassion (karuna). — Mahavairocana Sutra

To say that Zen is mystical Buddhism is not to suggest that William James’ characterizations of mysticism is the final word. What William James touches on is a profile of mysticism, or what he imagines mysticism to be from a study of its literature. But his characterizations of mysticism, namely, 1)ineffability; 2) noetic quality; 3) transience; 4)passivity, are only half accurate. Neither transience nor passivity are mystical traits—at least not for Zen.

Zen's mysticism consists of the personal discovery of the animative power that gives life to one’s corporeal body. Paradoxically, it is like searching for light with a lighted candle. Of its nature or substance, this animative power is an undying, universal medium which leaves no trace of itself, except that when the Zen mystic remembers (bodhi) it, he discovers that he has always been "It", it being tathata. In his ecstasy he has gone to tathata, who is thus, a Tathagata.

Now, instead of being a passive victim of transience existence, the Zen mystic is a part of active inspiriting power, that is, compassion. Christians might call such "God's love". This inspiriting power is like the light of the sun in its openness and acceptance of all forms of being. It also points the way to ultimate salvation.

What is more important, is that this discovery is like finding another organ besides the organs we have presently. It is an objective experience, in other words. This organ permits us to be of the animative light and still utilize the body. This, by the way, explains the seemingly bizarre behavior of Zen masters when being asked questions related to enlightenment. For example.

A monk asked: “It is said that the true teaching has not form. But when there is no master and no pupil, how is it then?

Joshu said: “Who made you come and ask this question?”

The monk said: “No one in particular.”

At that response, Joshu hit the student.

Joshu, aware of the the animative light, and borrowing from Bodhidharma (“That which asks is your Mind”) was testing the spiritual depth of this student. But of course, the student responded incorrectly—showing no ability to turn the tables on Joshu and show that he, also, is aware of this light. And so the student is punished.

Zen’s mysticism is perhaps the most profound form of mysticism of all the religions in the world. It verges on a science while, at the same time, recognizing that the ordinary human mind, if given the chance, can merge with the absolute and express this gnosis/satori in everyday life and in the arts.