How many of us have pictured God as a white-bearded man sitting on a throne in the sky?

One goal of Kabbalah, or Jewish mysticism, says Professor Daniel Matt of Berkeley's Graduate Theological Union, is to challenge such visions. "If we just blindly accept naive conceptions of God, we end up being frustrated with them and then wanting to throw the whole thing out."

Kabbalah, a body of Jewish mystical teachings of rabbinical origin, strives to heighten man's consciousness of a Divine presence in the universe. Among its main tenets is Ein Sof, the notion of God as an infinite, transcendent presence that is utterly unknowable and unreachable. Matt elucidates the concept in his new book, "The Essential Kabbalah: The Heart of Jewish Mysticism."

The book is essentially a "best of" collection, presenting analyses and historical information on the centuries-old Kabbalah, and translations of passages that illuminate key beliefs. The excerpts span the third to 20th centuries.

"If you are enlightened, you know God's oneness," a Kabbalah passage in Matt's book reads. "You know that the divine is devoid of bodily categories — these can never be applied to God…Then you wonder, astonished: Who am I?"

The kabbalistic notion of God as an omnipresent force, in fact, might help answer that existential question. Kabbalah teaches that the 10 Sefirot, or attributes that emanate from God, are also qualities that humans can emulate. These include understanding, wisdom, love and compassion –traits that if expressed on earth, kabbalists say, spark the Divine.

"One of [Kabbalah's] insights is that God is in need of the human being," Matt explained in an interview this week. "Righteous, ethical actions in the world are what make God whole."

Like most forms of religious mysticism, Kabbalah bases its teachings on man's communion with God. Kabbalah also focuses on the relationship between God and creation, the nature of good and evil, and reaching spiritual harmony through meditative techniques such as the repetition of Hebrew letters or divine names.

Though Jewish mystical philosophy appeared as early as the third century, Kabbalah did not emerge in its own right until the 12th century in Provence, France. Originally seen as an interesting but aberrant addition to mainstream Jewish thought, it later appealed to the masses, becoming a popular religious movement in the 16th century and surfacing again in the 18th century with the birth of Chassidism.

Matt, a professor at GTU's Center for Jewish Studies since 1979, first delved into Kabbalah 25 years ago during a college year in Jerusalem. "I felt a very intense spirituality there and I was looking for that element in Judaism," the 44-year-old Berkeley resident recalled.

Increasingly, it appears others are looking for similar connections. Though practicing kabbalists are mostly limited to groups in Israel, New York and London, some of the movement's notions have recently emerged more widely in the Jewish Renewal Movement and other branches of Judaism seeking heightened spirituality.

HarperSanFrancisco, which published "The Essential Kabbalah," has sold out the 9,000-run first printing in less than a month; readings at such mainstream bookstores as Barnes and Noble and Borders have drawn crowds of 30 to 40, a surprising number for a rather esoteric subject. "It really shows there's a hunger beyond the Jewish world," Matt said.

Matt, who previously wrote a book on Zohar, the chief work of Kabbalah, said Kabbalah underlies the way he sees his own world. "The ideas that are most striking I've tried to incorporate into my own day to day life, looking for the divine spark in my children, my wife, friends and strangers," he said. "That doesn't always work, but it works often enough that it has kept with me."

Traditionally, restrictions have been placed on access to Kabbalah, with Kabbalah experts insisting that those who study it be a minimum age, be married and morally fit, and have already mastered other basic texts. This is not to hide Kabbalah from people, Matt explained, but to protect those who are not prepared for the traditions' potentially life-altering tenets.

"Letting go of traditional notions of God and self can be both liberating and terrifying," the professor writes in the introduction to "The Essential Kabbalah."

So as Matt invites readers into the world of Kabbalah, he offers these words from kabbalist Isaac of Akko: "Strive to see supernal light, for I have brought you into a vast ocean. Be careful! Strive to see, yet escape drowning."