Paraphrasing from The Kybalion chapter 4:
http://www.kybalion.org/kybalion.php?chapter=IV
The Hermetists believe and teach that THE ALL, "in itself," is and must ever be UNKNOWABLE. They regard all the theories, guesses and speculations of the theologians and metaphysicians regarding the inner nature of THE ALL, as but the childish efforts of mortal minds to grasp the secret of the Infinite. Such efforts have always failed and will always fail, from the very nature of the task.
1. THE ALL must be ALL that REALLY IS. There can be nothing existing outside of THE ALL, else THE ALL would not be THE ALL.
2. THE ALL must be INFINITE, for there is nothing else to define, confine, bound, limit or restrict THE ALL. It must be Infinite in Time, or ETERNAL
3. THE ALL must be IMMUTABLE, or not subject to change in its real nature, for there is nothing to work changes upon it; nothing into which it could change, nor from which it could have changed. It cannot be added to nor subtracted from; increased nor diminished
THE ALL being Infinite, Absolute, Eternal and Unchangeable it must follow that anything finite, changeable, fleeting, and conditioned cannot be THE ALL.
What is there then higher than Matter or Energy that we know to be existent in the Universe? LIFE AND MIND! Life and Mind in all their varying degrees of unfoldment! "Then," you ask, "do you mean to tell us that THE ALL is LIFE and MIND?" Yes! and No! is our answer. If you mean Life and Mind as we poor petty mortals know them, we say No! THE ALL is not that! "But what kind of Life and Mind do you mean?" you ask.
The answer is "LIVING MIND, as far above that which mortals know by those words, as Life and Mind are higher than mechanical forces, or matter — INFINITE LIVING MIND as compared to finite Life and Mind." We mean that which the illumined souls mean when they reverently pronounce the word: "SPIRIT!"
"THE ALL" is Infinite Living Mind — the Illumined call it SPIRIT!