One day, years ago, I was sitting in a restaurant reading the following paragraph from page 151 of Daniel C. Matt's "The Essential Kabbalah: The HEART OF JEWISH MYSTICISM":
As my eyes passed over the words 'There is no path greater than this,' I experienced a seemingly-infinitely deep rumble from the center of my being! I laid my hands open flat on the table in an attempt to hold onto it for as long as possible. I intuitively knew that it was the Ein Sof spoken of in mystical Kabbalistic literature, in which I had had very little exposure. I had read that the Kabbalah was very powerful and felt that it was probably best left alone by someone like myself, that had been raised in liberal Christianity but who knew little about the Old Testament or historical Judaism.
Ein Sof is, metaphysically speaking, the highest form of God, the Impersonal God Beyond God that was the Infinite Reality present with nothing else—before taking on a personality, a name, or before creating or taking on any relationship with any world—Meister Eckhart's Godhead, silent desert, and dark stillness. Eckhart famously risked condemnation and execution by distinguishing between the Impersonal Godhead and the Person of God, who acts, creates, and hears prayers. Ein Sof is called the "divine ground of being" by protestant theologian Paul Tillich, and described as the Principle (with all else, including the Personal God, belonging to Manifestation or Radiance) by the Traditionalist Wisdom school of the Perennial Philosophy.