The Middle Pillar is a healing and energizing meditation, an energy yoga from The Western Tradition. Body centers represented by The Tree of Life are awakened and harmonized, then the Life Energy is circulated through the body as a bridge between the Earth and Sky. The energy is then passed from person to person, circulated as it was through the body.
First envisioned by the ancient Rabbis who delineated the Universe into a meditative diagram of (roughly) ten spheres or energy centers, it was occasionally superimposed upon the human body in artwork and stained glass. In the brief Renaissance that took place in Spain in the 1400s, Rabbis, Priests and Muslim clerics cooperated and the Rose Cross ritual was added to the meditation. In the late 1800s, The Golden Dawn reworked it in the light of ceremonial magick, and a member of one of its offshoots, Dr. Israel Regardie wrote several books on his adaptation.
The study of the Qabalah is complex and I could not hope to give a comprehensive description of it here. Volumes have written on the Tree of Life over several centuries, and people continue to study it. The Tree of Life is a "map" of the universe in a metaphysical sense. It describes the connection between the Divine and the mundane. Because of this, it is also considered by some to describe the forms that the universe took as God/dess was creating it. But if you believe that the God/dess and the universe are inseparable, that they coexist and that one could not exist without the other, then you will see a relationship in the Tree between the Divine and the mundane that is more Subtle than it first appears. Energy flows in many directions in the Tree of Life, including up and down. The energy flowing up the Tree from us is just as important as the energy flowing down the Tree from the Divine. But the Tree does not just describe the outer universe, it also describes the inner universe, the universe of our internal selves. The Tree is a map of our psychological, psychical and spiritual worlds.
The Hebrew in this site is read from right to left, but it's English transliteration is read from left to right, as are the languages themselves. The Home Page shows an example of this in the Rose Cross preview.