Veils of Negative Existence.
Within the Mystical system of the Qabalah, there are three Veils of Negative Existence:
Ain Soph (“Without Limit”)
Ain Soph Aur (“Limitless Light”)
Within, or beyond, these Veils are everything that is not. In a sense, they represent Pre-Existence, the state of all things before they make their initial Manifestation in Kether, the first Sephira, or Sphere of Existence. There are three Qabalistic Veils of the Negative Existence, and in themselves they formulate the Hidden Ideas of the Sephiroth not yet called into being, and they are concentrated in Kether, which in this sense is the Malkuth of the hidden ideas of the Sephiroth. The Limitless Ocean of Negative Light does not proceed from a Centre, for it is Centreless, but it concentrates a Centre, which is the number one of the Sephiroth, Kether, the Crown, the First Sephira; which therefore may be said to be the Malkuth or the number ten of the hidden Sephiroth. Thus, Kether is in Malkuth and Malkuth is in Kether.
First is Nothing, or the Absence of Things, אין [Ain], which does not and cannot mean Negatively Existing. Second is Without Limit אין סוף [Ain Soph] “i.e.”, Infinite Space. This is the primal Dualism of Infinity; the infinitely small and the infinitely great. The Clash of these produces a finite positive Idea which happens to be Light, אור [Aur]. This word [Aur] is most important. It symbolises the Universe immediately after Chaos, the confusion or Clash of the Infinite Opposites. א [Aleph] is the Egg of Matter; ו [Yod] is Taurus, the Bull, or Energy-Motion; and ר [Resh] is the Sun, or organised and moving System of Orbs. The three Letters of [Ain] thus repeat the three Ideas.
It is very difficult to explain the Negative Veils, because they represent a Reality (or lack thereof) that is, by definition, beyond human comprehension. Since it does surpass all finite understanding, immutable and boundless as its expanses are to the human Mind whose most profound speculation could not approach to the faintest adumbration of what It is in Itself, it must ever remain a mysterious Emptiness - Nothing.
Ain Soph is neither Spirit nor Will, but rather the underlying condition or material for both, as well as being the ultimate cause of Matter and Force. Such things come into spontaneous Existence from the Negative Veils because of Cyclic Law, which can be identified with the “Will to Manifest.” This law states that the Light [Ain] is normally in a state of Quiescence, moving in constant motion in a perfect Circle, as an Ouroboros. However, from time to time, the Light concentrates on itself and becomes polarized into Spirit and Matter. The mechanism for this process is unclear, so it cannot be understood in any reasonable sense. But whatever the method, the result of the process is the concentration of Infinite Light in Kether.