"When you look into the abyss, the abyss also looks into you" - Nietzsche
"Nothingness lies coiled in the heart of being - like a worm" - Sartre
In modern Kabbalah there is a well developed notion of an Abyss between the three supernal sephiroth of Kether, Chokhmah, and Binah, and the seven lower sephiroth. When one looks at the progress of the Lightning Flash down the Tree of Life, then one finds that it follows the path structure connecting sephiroth except when it makes the jump from Binah to Chesed, thus reinforcing this idea of a "gap" or "gulf" which has to be crossed. This notion of an Abyss is extremely old and has found its way into Kabbalah in several different forms, and in the course of time they have all been mixed together into the notion of "the Great Abyss"; the Great Abyss is one of those things so necessary that like God, if it didn't already exist, it would have to be invented.
One of the earliest sources for the Abyss comes from the Bible:
"And the earth was without form, and void; and darkness was upon the face of the deep."
Kabbalists adopted this view that there was a time before the creation characterised by Tohu and Bohu, namely Chaos and Emptiness . Another idea mentioned several times in the Zohar  is that there were several failed attempts at creation before the present one; these attempts failed because mercy and judgement (e.g. force and form) were not balanced, and the resulting detritus of these failed attempts, the broken shells of previous sephiroth, accumulated in the Abyss. Because the shells (Qlippoth) were the result of unbalanced rigour or judgement they were considered evil, and the Abyss became a repository of evil spirits not dissimilar from the pit of Hell into which the rebellious angels were cast, or the rebellious Titans in Greek mythology who were buried as far beneath the Earth as the Earth is beneath the sky.
Another theme which contributed to the notion of the Abyss was the legend of the Fall. According to the Kabbalistic interpretation of the Biblical myth, at the conclusion of the act of Creation there was a pure state, denoted by Eden, where the primordial Adam-and-Eve-conjoined existed in a state of divine perfection. There are various esoteric interpretations of what the Fall represents, but all agree that after the Fall Eden became inaccessible and Adam and Eve were separated and took on bodies of flesh here in the material world. This theme of separation from God and exile in a world of matter (and by extension, limitation, finiteness, pain, suffering, death - manifestations of the rigours or evil inherent in God) precedes Kabbalah and can be found in the Gnostic legend of Sophia exiled in matter. This idea of separation or exile from divinity mirrors very closely the use of the Abyss on the modern Tree to divide the sephiroth representing a human being from the sephiroth representing God.
Isaac Luria (1534 -1572) introduced a new element into the notion of the Abyss with his idea of "tzimtzum" or contraction. Luria wondered how it was possible for the hidden God (En Soph) to create something out of nothing if there wasn't any nothing to begin with. If the En Soph (no-end, the infinite) is everywhere then how can we be distinct from the En-Soph? Luria argued that creation was possible because a contraction in the En Soph had created an emptiness where God was not, that En Soph had chosen to limit itself by a withdrawal, and this showed that the principle of self-limitation was a necessary precursor to creation; not only did this explain why the Creation is separate from the hidden God, but it emphasised that limitation was inherent in creation from the very beginning. Limitation, finiteness, the separation of one thing from another, what early Kabbalists referred to as the severity or "strict judgement" of God (what modern Kabbalists call "form") was a puzzling quality to introduce into the Creation given that it is the source of suffering and evil in the impersonal sense, what Dion Fortune calls "negative evil" . Luria's notion of tsimtsum suggested that there was no possibility of creation without it, and provided a rather abstract explanation to one of the most persistent questions of all time, namely: "if God made the world and God is good, how come he made mosquitoes?".
Pull together the various ideas of the Great Abyss and one ends up with a sort of vast, initially empty arena like a Roman amphitheatre where the drama of the Creation was enacted. The mysterious En Soph played a brief role as director from the imperial box, only to retire behind a veil at the conclusion of the performance leaving behind a huge power cord snaking in from the unknown region beyond the arena, and plugged-in to a socket at the rear of the sephira Kether. The lights of the sephiroth blaze out and illuminate the centre of this vast arena; this is Olam Ha-Nekudoth, "The World of Point Lights". At the periphery of the arena far from the lights of manifestation there is a deep darkness where all the cast-off detritus and spoil of the creation was deposited by weary angels and left to rot. A strange life lives there.
The situation was more-or-less as described above when in 1909 Aleister Crowley decided to "cross the Abyss" and added to the mythology of the Abyss with the following description :
"The name of the Dweller in the Abyss is Choronzon, but he is not really an individual. The Abyss is empty of being; it is filled with all possible forms, each equally inane, each therefore evil in the only true sense of the word - that is, meaningless but malignant, in so far as it craves to become real. These forms swirl senselessly into haphazard heaps like dust devils, and each chance aggregation asserts itself to be an individual and shrieks `I am I!' though aware all the time that its elements have no true bond; so that the slightest disturbance dissipates the delusion just as a horseman, meeting a dust devil, brings it in showers of sand to the earth."
I was struck when reading this by the similarity between Crowley's description above and the section on Hod and Netzach in which I described the chaos of a personality under the control of the "hosts" or "armies" of those two sephira, where a host of forms of behaviour compete for the right to be "me". Crowley's experience has far more in common with the rending of the Veil of Paroketh separating Yesod and Tiphereth, and further comments by Crowley add weight to this:
"As soon as I had destroyed my personality, as soon as I had expelled my ego, the universe to which it was indeed a frightful and fatal force, fraught with every form of fear, was only so in relation to the idea `I'; so long as `I am I' all else must seem hostile. Now that there was no longer any `I' to suffer, all these ideas which had inflicted suffering became innocent. I could praise the perfection of every part; I could wonder and worship the whole."
This is a very recognisable description of someone who has been released from the demon of the false self and the imprisoning triad of Hod, Netzach and Yesod, and moved through the Paroketh towards Tiphereth. Crowley's experience is valid as it stands, but what it might mean to "cross the Abyss", and the absurdity of Crowley's belief that he had achieved this, will be examined in the following section on Binah and Chokhmah.
A twentieth-century Kabbalist who did succeed in adding something useful to the ever-expanding notion of the Abyss was Dion Fortune, in her theosophical work "The Cosmic Doctrine" . The form of this work appears to have been inspired by Blavatsky's "The Secret Doctrine", and certainly lives up to Fortune's claim that it was "designed to train the mind, not to inform it."
Fortune describes three processes arising out of the Unmanifest (i.e. En Soph). Ring Cosmos is an anabolic process underlying the creation of forms of greater and greater complexity. Ring Chaos is a catabolic process underlying the destruction and recycling of form. Ring-Pass-Not is a limit where catabolism turns back into anabolism. She visualised this as three great rings of movement in the Unmanifest, with the motion associated with Ring Cosmos spiralling towards the centre, the movement of Ring Chaos unwinding towards the periphery, and the dead-zone of Ring-Pass-Not defining the outer limit of Ring Chaos as an abyss of unbeing, a cosmic compost heap where form is digested under the dominion of the Angel of Death and turned into something fertile where new growth can take place.
The similarity between Fortune's description of Ring Chaos and what in programming is called a "reference-counting garbage collector" is remarkable, given that she was writing in the 30's. Many programming languages allow new programming structures to be created dynamically, thus allowing the creation of more and more complex structures. At the same time there is a mechanism to reclaim unused resources so that the system does not run out of memory or disc space, and the normal scheme is that if a structure is not referenced by any other structure, recycle it. In Fortune's language, if you want to destroy something, you "make a vacuum round it (i.e. remove all references). You prevent opposition from touching it. Then, being unopposed, it is free to follow the laws of its own nature, which is to join the motion of Ring Chaos."
"Cosmic Doctrine" is a valiant attempt to say something quite profound; at an intellectual level it fails "abysmally", and I cannot read it without squirming, but it still has more raw Kabbalistic and magical insight at an intuitive level than just about anything else I have read. The idea of a cosmic reference-counting garbage collection process and an abyss of unbeing which is not so much a state as a process of unbecoming is something not easily forgotten once touched.
A final example of an abyss is one which differs from the previous examples in that it brings to the fore the relationship between us, the created, and the Unmanifest, the En Soph itself. Kabbalistic writers agree that the Unmanifest is not nothing; on the contrary, it is the hidden wellspring of being, but as it is "not manifest being" it combines the words "not" and "being" in a conjuction which can be apprehended as a kind of abyss. Scholem  discusses this "nothingness" as follows:
"The primary start or wrench in which the introspective God is externalised and the light that shines inwardly made visible, this revolution of perspective, transforms En Soph, the inexpressible fullness, into nothingness. It is in this mystical "nothingness" from which all the other stages of God's gradual enfolding in the Sefiroth emanate, and which the kabbalists call the highest Sefira, or the "supreme crown" of Divinity. To use another metaphor, it is the abyss which becomes visible in the gaps of existence. Some Kabbalists who have developed this idea, for instance Rabbi Joseph ben Shalom of Barcelona (1300), maintain that in every transformation of reality, in every change of form, or every time the status of a thing is altered, the abyss of nothingness is crossed and for a fleeting mystical moment becomes visible."
It should be clear by now that the Abyss is a metaphor for a number of intuitions or experiences. I do not know how many different kinds of abyss there are, but there are some distinctions which can be made:
The perception that being and nothingness go hand-in-hand is something Sartre studied in great depth , and many of his observations on the nature of consciousness and its relatationship to negation or nothingness are among the most perceptive I have found. His arguments are lengthy and complex, and I do not wish to summarise them here other than to say that he viewed nothingness as the necessary consequence of a special kind of being he calls "being-for-itself", the kind of being we experience as self-conscious human beings.
The Abyss of separation can be experienced as a separation from the divine, but it can also be experienced quite acutely in one's relationships with others and with the physical world itself. Much of what we perceive about the world and other people is an illusion created by the machinery of perception; strip away the trick, Yesod becomes Daath, and a yawning abyss opens up where one is conscious less of what one knows than of what one does not; it is possible to look at a close friend and see something more alien, remote and unknown than the surface of Pluto. This experience is closely related to the Abyss of knowledge, which is discussed in more detail in the discussion on Daath below.
The Abyss of un-being is the direct perception that at any instant it is possible to not-be. This perception goes beyond the contemplation or awareness of physical death; it is the direct apprehension of what Dion Fortune calls "Ring Chaos", that un-being is less a state than a process, that at every instant there is an impulse, a magnetic attraction towards total self-annihilation on every level possible. The closer one moves towards the roots of being, the closer one moves towards the roots of un-being.
Daath means "Knowledge". In early Kabbalah Daath was a symbol of the union of Wisdom (Chokhmah) and Understanding (Binah). The book of Proverbs is rich mine of material on the nature of these three qualities, material which forms the basis of many ideas in the Zohar and other Kabbalistic texts; e.g. Proverbs 3.13:
"Happy is the man that findeth wisdom, and the man that getteth understanding....She is a tree of life to them that lay hold upon her: and happy is every one that retaineth her. The Lord by wisdom hath founded the earth; by understanding hath he founded the heavens. By his knowledge the depths are broken up, and the clouds drop down the dew"
And Proverbs 24.3:
"Through wisdom is an house builded; and by understanding is it established: And by knowledge shall the chambers be filled with all pleasant and precious riches."
In the "Bahir"  and "Zohar" [e.g. 2] Daath represents the symbolic union of wisdom and understanding, and is their offspring or child. As the Microprosopus, often symbolised by Tiphereth, is also the symbolic child of Chokhmah and Binah, there is some room for confusion. According to the Zohar however, Daath has a specific location in the Microprosopus, namely in one of the three chambers of the brain, from where it mediates between the higher (Chokhmah and Binah) and the lower (the six sephiroth or "chambers" of the Microprosopus - see the reference to Proverbs 24.3 above).
I have often puzzled as to why knowledge is the natural outcome of wisdom and understanding. It was only recently when I read Proverbs that I realised that wisdom was being used in the sense of something external, something which is received from someone else. As children we were told "do this" or "don't do that", and often couldn't question the wisdom of the advice because we lacked the understanding. I once had a furious row with my father about building a liquid fuel rocket engine in the house using petrol and hydrogen peroxide. He flatly refused to let me do it. I couldn't understand the problem - I was going to be careful. I now know, because I understand the stupidity of what I was trying to do, the wisdom of his refusal. Received wisdom cannot be integrated into oneself unless there is the capacity to understand it, and having understood, it becomes real knowledge which can be passed on again as wisdom to someone else. For early Kabbalists the ultimate wisdom was the wisdom of God as expressed in the Torah, and by attempting to understand this wisdom (and that is what Kabbalah was) they could arrive at the only knowledge truely worth having. Knowledge of God was the union between the higher and lower, and perhaps this is why Daath was never a sephiroth, something which manifests positively; since the Fall that knowledge has been lost. One of the unattributable pieces of Kabbalah I was taught was that Daath is the hole left behind when Malkuth fell out of the Garden of Eden. If you examine my derivation of the Tree of Life in Chapter 1. closely you will see that I have based some of it on this very astute observation.
The notion of Daath as a "hole" appears to have originated this century. Gareth Knight, for example , provides a complete set of correspondences for Daath, many of which happen to be negative Tiphereth correspondences or misplaced correspondences borrowed from other sephiroth, but one at least is appropriate: he gives the magical image of Daath as Janus, god of doorways. Kenneth Grant , with his usual florid imagination, sees Daath as a gateway through to "outer spaces beyond, or behind, the Tree itself" dominated by Qlippothic forces.
There is a deep correspondence between sephiroth in the lower face of the Tree and sephiroth in the upper face: look at the symmetry of the Tree and you should see why Malkuth, Tiphereth and Kether are linked, why Hod and Binah are linked, why Chokhmah and Netzach are linked, and most importantly for the purposes of this discussion, that there is a correspondence between Yesod and Daath. These are not just simple geometric symmetries; they express some important relationships which are experientially verifiable, and in terms of what makes most sense in Kabbalah and what does not, these relationships are important. Daath and Yesod, at different levels, are like two sides of the same coin. Jam the machinery of perception I said above, and Yesod can become Daath. The following quotation is taken from an bona-fide anthropological article  attempting to explain some of the characteristic features of cave art:
"Moving into a yet deeper stage of trance is often accompanied, according to laboratory reports, by an experience of a vortex or rotating tunnel that seems to surround the subject. The external world is progressively excluded and the inner world grows more florid. Iconic images may appear on the walls of the vortex, often imposed on a lattice of squares, like television screens. Frequently there is a mixture of iconic and geometric forms. Experienced shamans are able to plunge rapidly into deep trance, where they manipulate the imagery according to the needs of the situation. Their experience of it, however, is of a world they have come briefly to inhabit; not a world of their own making, but a spirit world they are privileged to visit."
This will come as no surprise to anyone who has read Michael Harner's "The Way of the Shaman" . There on page 103 (plate 8) is a beautiful picture of the tunnel vortex, complete with prisms. When I first saw this picture I was astonished and recognised it instantly, prisms and all; when I showed it to my wife her reaction was the same. The tunnel vortex appears to be one of the constants of magical/mystical experience, and it appears in a very precise context. In Kabbalah the shamanic tunnel would be attributed to the 32nd. path connecting Malkuth to Yesod; this path connects the real world to the underworld of the imagination and the unconscious, and is commonly symbolised by a tunnel [eg.9]. However, using the symmetry of the Tree, this path also corresponds to the path at another level connecting Tiphereth across the Abyss, through Daath, to Kether. The tunnel/vortex at this level is no longer subjective, because this level of the Tree corresponds to the noumenal reality underpinning the phenomenal world, and links individual self-consciousness to something greater. Just as Yesod represents the machinery of sense perception, so Daath can flip over to become the Yesod of another level of perception, not sense perception, but something completely different that seems to operate out of the "back door" of the mind; this is objective knowledge, what used to be called gnosis.
To conclude this section on Daath and the Abyss, it is worth asking what the relationship between the two ideas is. As I programmer I am continually aware of the gulf between abstract ideas, such as the number two and its physical representations in the world: 2, II, .., two etc. The number two can be represented in an infinite number of ways, and it is only when you share some understanding of my language that you can begin to guess that a particular mark in the world represents the number two. The situation is even worse than it might seem; a basic theorem of information theory states that the optimum way of expressing any piece of information is one where the symbols occur completely randomly. I could take this paragraph, pass it through an optimal text compressor and the same piece of text would be indistinguishable from random garbage. Only I, knowing the compression procedure, could extract the original message from the result. Whatever we call information appears to exist independently of the physical world, and uses the world of chalk marks, ink marks, magnetic domains or whatever like a rider uses a horse. To me, the gulf is irreconcilable; between the physical world and the world of the mind is an abyss, and I am not indulging in "new physics" or anything vaguely suspect - this is meat and drink to the average progammer, who spends most of his or her time transforming abstractions from one symbol set to another.
To take a slightly different approach, there is a mathematical proof that there is no largest prime number. I know that proof. No dissection of my brain will ever reveal the proof to someone who does not know it. I am prepared to bet a large quantity of alcohol that it is theoretically impossible to discover; the proof that there is no largest prime number will never be extracted even if you assume a neurologist capable of mapping every atom in my brain. Evolution tends towards optimality, and I think the proof will be encoded optimally to look like random garbage. There is an abyss here; there is knowledge which can never be attained. In Kabbalah this particular abyss is called the abyss of Assiah; it is the first in a series of abysses. The next abyss is the abyss of Yetzirah, and it is this abyss I have been discussing for most of this section. There are further abysses, and this should be clearer when I discuss the Four Worlds and the Extended Tree. The Abyss and Daath go together because the Abyss sets a limit on what can be known from below the Abyss; the abyss is an abyss of knowledge, and Daath is the hole we fall into when we try probe beyond. Can the nature of God be expressed in terms of anything human? No. God is as human as a cockroach, as human as a lump of stone, as human as a star, as human as empty space. So how can you know anything about God? Only when Daath flips over to become the Yesod of another world can you know anything, but unfortunately the fiery speech of angels is like leprecaun's gold: by the time you've taken it home to show to your friends, you've nothing but a purse of dried leaves.