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Within the modern system of Thelema, developed by occultist Aleister Crowley in the first half of the 20th century, Thelemic mysticism is a complex mystical path designed to do two interrelated things: to learn one's unique True Will and to achieve union with the All. The set of techniques for doing so falls under Crowley's term Magick, which draws upon various existing disciplines and mystical models, including Yoga, Western ceremonial ritual (especially invocations and eucharistic ceremony), the Qabalah, and several divination systems, especially the tarot and astrology.
The path to mystical attainment or enlightenment was initially developed by Crowley largely based on the meditation/mystical techniques found in Buddhism and also the Tree of Life, especially as it was examined by Eliphas Levi in the 19th century and later by various members in the occult society, the Golden Dawn. In 1904, Crowley claimed to have transcribed, via "direct-voice transmission" from a "praeternatural intelligence" named Aiwass, The Book of the Law, which he eventually called the central sacred text of Thelema, heralding a new Aeon for mankind.
Between 1907 and 1911, Crowley wrote a series of other small texts which he considered to be "inspired" in that they were written through him rather than by him, which were afterwards collected together and termed the Holy Books. The final text added to the list was The Vision and the Voice, a vivid account of Crowley's astral travels through the thirty Enochian Aethyrs. These texts formed the final mystical backbone of Crowley's system.
Within the system that Crowley developed, the core task for the adept is the discovery and manifestation of Will, defined at times as a grand destiny and at other times as a moment to moment path of action that operates in perfect harmony with Nature. This Will does not spring from conscious intent, but from the interplay between the deepest Self and the entire Universe. Therefore, the enlightened Thelemite is one who is able to eliminate or bypass the consciousness-created desires, conflicts, and habits, and tap directly into the Self/Universe nexus. Theoretically, at this point, the Thelemite acts in alignment with Nature, just as the stream flows downhill, with neither resistance nor "lust of result."
The ability to accomplish this Great Work requires a great deal of preparation and effort, according to Crowley's system. The programme consists of several key elements, including a thorough knowledge of the Hermetic Qabalah (especially the Tree of Life), disciplined concentration (i.e. meditation), the development of one's Body of Light (or astral body) (in order to experience other spiritual realms) and the consistent and regular invocation of certain deities or spiritual beings.
Learning the Tree of LifeEdit
The Tree of Life is a tool used to categorize and organize various mystical concepts. At its most simple level it is composed of ten spheres, or emanations, called sephiroth (sing. "sephira") which are connected by twenty-two paths. The sephiroth are represented by the planets and the paths by the characters of the Hebrew alphabet, which are subdivided by the five elements, the seven classical planets, and the twelve signs of the Zodiac.
Within the western magical tradition, the Tree is used as a kind of conceptual filing cabinet. Each sephira and path is assigned various ideas, such as gods, cards of the Tarot, astrological planets and signs, elements, etc. Within Thelema, the seminal book which defines all these correspondences is Crowley's Liber 777, although there have been other influential writers on the topic, including Israel Regardie and Eliphas Levi.
The path of attainment is largely defined by the Tree of Life. The aspirant begins in Malkuth, which is the everyday material world of phenomena, with the ultimate goal being at Kether, the sphere of Unity with the All. Through various exercises and practices, he or she attains certain spiritual and mental states that are characterized by the various sephiroth that ascend the Tree. Crowley considered a deep understanding of the Qabalah to be essential to the Thelemite:
The Tree of Life has got to be learnt by heart; you must know it backwards, forwards, sideways, and upside down; it must become the automatic background of all your thinking. You must keep on hanging everything that comes your way upon its proper bough.
The art of using it consists principally in referring all our ideas to it, discovering thus the common nature of certain things and the essential differences between others, so that ultimately one obtains a simple view of the incalculably vast complexity of the Universe.
The whole subject must be studied in the Book 777, and the main attributions committed to memory: then when by constant use the system is at last understood—as opposed to being merely memorised—the student will find fresh light break in on him at every turn as he continues to measure every item of new knowledge that he attains by this Standard. For to him the Universe will then begin to appear as a coherent and a necessary Whole.
Part of the reason why the Qabalah is so important is that it is the key to understanding the Holy Books. Most of them, including The Book of the Law, are written in abstract, poetic, and often obscure language. Through the use of the Qabalah, and especially the function of gematria (a form of numerology), the normally opaque meaning of the texts can be made clear. Thelemites can also make use of gematria to link words and concepts and to validate revelations given to them in magical operations, such as astral travel.
Another key element to Thelemic mysticism is the ability to concentrate. This skill has two modalities: the first is the rapid, accurate, and efficient movement of thought (which is the realm of magick) and the other is the stopping of thought altogether (which is accomplished in Yoga). In the first, it is the manipulation of all ideas into one idea, and in the second is the taking of that one thought and reducing it to nothing. Of this skill, Crowley writes:
For concentration does indeed unlock all doors; it lies at the heart of every practice as it is of the essence of all theory; and almost all the various rules and regulations are aimed at securing adeptship in this matter. All the subsidiary work—awareness, one-pointedness, mindfulness and the rest—is intended to train you to this.
Concentration is essentially the prerequisite for all sustained success, not only in spiritual practices, but in day-to-day life as well. The general program for developing concentration is borrowed almost completely from the practice of Yoga within the Hindu and Buddhist systems. Crowley gives a general overview of the techniques in two books: Eight Lectures on Yoga  and in the section called "Mysticism" in his opus, Magick (Book 4).
Body of Light and astral travelEdit
The Body of Light—Crowley's term for the subtle body—is the theoretical aspect of self that can leave the corporeal body and carry one's senses and consciousness during astral travels. Crowley writes of it in Book 4: "The work of the Body of Light—with the technique of Yoga—is the foundation of Magick."
The Body of Light must be developed and trained with exactly the same rigid discipline as the brain in the case of mysticism. The essence of the technique of Magick is the development of the Body of Light, which must be extended to include all members of the organism, and indeed of the cosmos [...] The object is to possess a Body which is capable of doing easily any particular task that may lie before it. There must be no selection of special experience which appeals to one's immediate desire. One must go steadily through all possible pylons.
Crowley explains that the most important practices for developing the Body of Light are:
- The fortification of the Body of Light by the constant use of rituals, by the assumption of god-forms, and by the right use of the Eucharist.
- The purification and consecration and exaltation of that Body by the use of rituals of invocation.
- The education of that Body by experience. It must learn to travel on every plane; to break down every obstacle which may confront it.
The benefit of astral travel is essentially one of education...it is akin to exploring one's own spiritual universe ("Every Magician possesses an Astral Universe peculiar to himself") and understanding the fundamental components, so that the adept can eventually master it. The general object is the "control of the Astral Plane, the ability to find one's way about it, to penetrate such sanctuaries as are guarded from the profane, [and] to make such relations with its inhabitants as may avail to acquire knowledge and power, or to command service". Also, "one's apprehension of the Astral Plane must be accurate, for Angels, Archangels, and Gods are derived therefrom by analysis. One must have pure materials if one wishes to brew pure beer." It is vital to understand that all this must be in service to the Great Work of discovering one's True Will:
Let the Magician therefore adventure himself upon the Astral Plane with the declared design to penetrate to a sanctuary of discarnate Beings such as are able to instruct and fortify him, also to prove their identity by testimony beyond rebuttal. All explanations other than these are of value only as extending and equilibrating Knowledge, or possibly as supplying Energy to such Magicians as may have found their way to the Sources of Strength. In all cases, naught is worth an obol save as it serve to help the One Great Work"
Crowley was also willing to admit that what was experienced during "astral travel" was not relevant in terms of what is "real" or "unreal." Ultimately, the only value to this practice is in the utility it provides to the adept.
The 'reality' or 'objectivity' of these symbols is not pertinent to the discussion. [...] The Magician must not accept [my] account of the Astral Plane, [my] Qabalistic discoveries, [my] instructions in Magick. They may be correct in the main for most men; yet they cannot be wholly true for any save [myself], even as no two artists can make identical pictures of the same subject [...] What one sees and hears is 'real' in its way, whether it be itself, or distorted by one's desires, or created by one's personality [...] The true, the final test, of the Truth of one's visions is their Value. The most glorious experience on the Astral plane, let it dazzle and thrill as it may, is not necessarily in accordance with the True Will of the seer; if not, though it be never so true objectively, it is not true for him, because not useful for him.
The Body of Light is more important than simply for astral travel—it is the storehouse of all experiences.
In Magick, on the contrary, one passes through the veil of the exterior world (which, as in Yoga, but in another sense, becomes "unreal" by comparison as one passes beyond) one creates a subtle body (instrument is a better term) called the Body of Light; this one develops and controls; it gains new powers as one progresses, usually by means of what is called 'initiation': finally, one carries on almost one's whole life in this Body of Light, and achieves in its own way the mastery of the Universe.
According to Crowley, there is a single definition of the purpose for ritual magick: to achieve Union with God through "the uniting of the Microcosm with the Macrocosm."  Since this process is so arduous, it is also acceptable to use magick to develop the self (i.e. one's Body of Light) or to create ideal circumstances for the Work (e.g. having access to a place in which to do ritual undisturbed). There are many kinds of magick, but the categories of ritual that are recommended by Crowley include (all quotes are from Book 4):
- Banishing—the elimination of unwanted forces. "The Magician must therefore take the utmost care in the matter of purification, firstly, of himself, secondly, of his instruments, thirdly, of the place of working."
- Invocation, where the magician identifies with the Deity invoked. There are three methods:
- Devotion —where "identity with the God is attained by love and by surrender, by giving up or suppressing all irrelevant (and illusionary) parts of yourself." (e.g. Liber Astarte )
- Calling forth—where "identity is attained by paying special attention to the desired part of yourself: positive, as the first method is negative." (e.g. assumption of god-forms)
- Drama—where "identity is attained by sympathy. It is very difficult for the ordinary man to lose himself completely in the subject of a play or of a novel; but for those who can do so, this method is unquestionably the best." (e.g. many initiations and the Gnostic Mass)
- Evocation—which is bringing a spiritual being before, not into, the magician (e.g. Goetia)
- Eucharistic ritual—which "consists in taking common things, transmuting them into things divine, and consuming them." (e.g. The Mass of the Phoenix )
- Consecration—"the active dedication of a thing to a single purpose."
- Divinations—such as the use of the Tarot or other tools used to gather information.
Mystical milestones within the A.A. SystemEdit
Crowley often wrote that every adept's path will be unique. He also wrote that two major milestones are fundamental to Thelemic mysticism, which he called the knowledge of and conversation with one's Holy Guardian Angel and the crossing of the Abyss. Crowley wrote, "the two crises—the Angel and the Abyss—are necessary features in every career. The other tasks are not always accomplished in [any given order]".
The Holy Guardian AngelEdit
Even though the Holy Guardian Angel (or HGA) is, in a sense, the “higher self”, it is often experienced as a separate being, independent from the adept. In the system of the A∴A∴ magical order, the single most important goal is to consciously connect with one’s HGA, a process termed “Knowledge and Conversation.” By doing so, the magician becomes fully aware of his own True Will. For Crowley, this event was the single most important goal of any adept:
It should never be forgotten for a single moment that the central and essential work of the Magician is the attainment of the Knowledge and Conversation of the Holy Guardian Angel. Once he has achieved this he must of course be left entirely in the hands of that Angel, who can be invariably and inevitably relied upon to lead him to the further great step—crossing of the Abyss and the attainment of the grade of Master of the Temple.
In most of his writings, Crowley described the Holy Guardian Angel as one's "Silent Self", at times equitable with one's deepest unconscious. In later writings, he insisted that the HGA is an entirely separate and objective being. Whichever position is taken, the object remains the same—to gain an intimate spiritual connection so that one's True Will can become fully known and manifested. When using the Tree of Life as a guide, this event occurs in the Sphere of Tiphareth.
Crowley wrote Liber Samekh  as an example of a ritual designed specifically for attaining the Knowledge and Conversation with one’s HGA. In his notes to this ritual, Crowley sums up the key to success: “INVOKE OFTEN.” Another detailed description of the general operation is given in The Vision and the Voice, Aethyr 8 .
Crossing the AbyssEdit
After one attains Knowledge and Conversation with the Holy Guardian Angel, the adept may choose to then reach the next major milestone: the crossing of the Abyss, the great gulf or void between the phenomenal world of manifestation and its noumenal source, that great spiritual wilderness which must be crossed by the adept to attain mastery.
This doctrine is extremely difficult to explain; but it corresponds more or less to the gap in thought between the Real, which is Actual, and the Unreal, which is Ideal. In the Abyss all things exist, indeed, at least in posse, but are without any possible meaning; for they lack the substratum of spiritual Reality. They are appearances without Law. They are thus Insane Delusions.
Choronzon is the Dweller in the Abyss; he is there as the final obstruction. If he is met with the proper preparation, then he is there to destroy the ego, which allows the adept to move beyond the Abyss. If unprepared, then the unfortunate traveller will be utterly dispersed into annihilation. Both Choronzon and the Abyss are discussed in Crowley's Confessions (ch. 66):
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 such 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.
However, just on the other side of the Abyss awaits Babalon. She calls the adept to surrender completely, so that he or she may cross over.
Babalon, the City of the Pyramids, and the Night of PanEdit
Choronzon is the dweller within the Abyss, and his purpose is to trap the traveller in a meaningless world of illusion. However Babalon is just on the other side, beckoning (in the sphere of Binah on the Tree of Life). If the adept gives himself to her—the symbol of this act is the pouring of the adept’s blood into her graal—he becomes impregnated in her (a state called "Babe of the Abyss"), then he is reborn as a Master and a Saint that dwells in the City of the Pyramids.
The City of the Pyramids is the home to those adepts that have crossed the great Abyss, having spilled all their blood in the Graal of Babalon. They have destroyed their earthly ego-identities, becoming nothing more than piles of dust (i.e. the remaining aspects of their True Selves without the self-sense of "I"). Within, they take on the name or title of Saint or Nemo (Latin for No-Man or No-One). In the system of A∴A∴ they are called Masters of the Temple. It is a step along the path of spiritual purification, and a spiritual resting place for those who have successfully shed their attachments to the mundane world.
Of these adepts, it is written in The Vision and the Voice (Aethyr 14):
These adepts seem like Pyramids—their hoods and robes are like Pyramids [...] And the Beatific Vision is no more, and the glory of the Most High is no more. There is no more knowledge. There is no more bliss. There is no more power. There is no more beauty. For this is the Palace of Understanding: for thou art one with the Primeval things.' 
The Master of the Temple accordingly interferes not with the scheme of things, except just so far as he is doing the Work which he is sent to do. Why should he struggle against imprisonment, banishment, death? [...] The Master of the Temple is so far from the man in whom He manifests that all these matters are of no importance to Him. It may be of importance to His Work that man shall sit upon a throne, or be hanged.
I was instantly blotted in blackness. Mine Angel whispered the secret words whereby one partakes of the Mysteries of the Masters of the Temple. Presently my eyes beheld (what first seemed shapes of rocks) the Masters, veiled in motionless majesty, shrouded in silence. Each one was exactly like the other. Then the Angel bade me understand whereto my aspiration led: all powers, all ecstasies, ended in this—I understood. He then told me that now my name was Nemo, seated among the other silent shapes in the City of the Pyramids under the Night of Pan; those other parts of me that I had left for ever below the Abyss must serve as a vehicle for the energies which had been created by my act. My mind and body, deprived of the ego which they had hitherto obeyed, were now free to manifest according to their nature in the world, to devote themselves to aid mankind in its evolution. In my case I was to be cast out into the Sphere of Jupiter. My mortal part was to help humanity by Jupiterian work, such a governing, teaching, creating, exhorting men to aspire to become nobler, holier, worthier, kinglier, kindlier and more generous.
The City exists under the Night of Pan, or N.O.X. The playful and lecherous Pan is the Greek god of nature, lust, and the masculine generative power. The Greek word Pan also translates as All, and so he is “a symbol of the Universal, a personification of Nature; both Pangenetor, "all-begetter," and Panphage, "all-devourer" (Sabazius, 1995). Therefore, Pan is both the giver and the taker of life, and his Night is that time of symbolic death where the adept experiences unification with the All through the ecstatic destruction of the ego-self. In a less poetic symbolic sense, this is the state where one transcends all limitations and experiences oneness with the universe.
Magus and IpsissimusEdit
Only a few reach the final two stages, The penultimate is the becoming of a Magus (symbolized by entering Chokmah on the Tree of Life), whose essential duty is to communicate a new Truth to mankind. Of the Magi, Crowley writes:
There are many magical teachers but in recorded history we have scarcely had a dozen Magi in the technical sense of the word. They may be recognized by the fact that their message may be formulated as a single word, which word must be such that it overturns all existing beliefs and codes. We may take as instances the Word of Buddha—Anatta (absence of an atman or soul) [...] Mohammed, again, with the single word Allah [...] Similarly, Aiwass, uttering the word Thelema (with all its implications), destroys completely the formula of the Dying God.
The state of being a Magus is described in Crowley's Liber B vel Magi.  Elsewhere, he admits the possibility of someone reaching this rank without uttering a new magick Word. Such a Magus, he says, would identify himself or herself with the Word of the current Aeon and work to establish it. In Magick Without Tears, Crowley suggests (without actually saying so) that the Secret Chiefs of the A∴A∴ have reached at least the rank of Magus, in some sense. 
The state of Ipsissimus is the very highest possible (symbolized by the sphere of Kether on the Tree of Life). Relatively little is openly written of this state of enlightenment
The Ipsissimus is wholly free from all limitations whatsoever, existing in the nature of all things without discriminations of quantity or quality between them. He has identified Being and not-Being and Becoming, action and non-action and tendency to action, with all other such triplicities, not distinguishing between them in respect of any conditions, or between any one thing and any other thing as to whether it is with or without conditions.
He is sworn to accept this Grade in the presence of a witness, and to express its nature in word and deed, but to withdraw Himself at once within the veils of his natural manifestation as a man, and to keep silence during his human life as to the fact of his attainment, even to the other members of the Order.
The Ipsissimus is pre-eminently the Master of all modes of existence; that is, his being is entirely free from internal or external necessity. His work is to destroy all tendencies to construct or to cancel such necessities. He is the Master of the Law of Unsubstantiality (Anatta)."
The Ipsissimus has no relation as such with any Being: He has no will in any direction, and no Consciousness of any kind involving duality, for in Him all is accomplished; as it is written 'beyond the Word and the Fool, yea, beyond the Word and the Fool'."
- Crowley, Magick Without Tears, ch. IV
- Crowley, Little Essays Towards Truth, "Man"
- Magick Without Tears, ch. XVI
- Crowley, ABA: chapter 21
- Crowley,Book 4, Apx. 3
- Crowley, Magick Without Tears, Ch. 81
- Confessions, ch.2
- Crowley, Magick Without Tears, Ch.83
- Crowley, Little Essays Towards Truth: Man
- Confessions, chapter 66
- Confessions, chapter 21
- Confessions, ch. 49
- Book 4, apx: II
- Crowley, Aleister. (1997). Magick: Book 4. 2nd ed. York Beach, Me. : S. Weiser.
- ___. (1979). The Confessions of Aleister Crowley. London;Boston : Routledge & Kegan Paul.
- ___. (1998). The Vision & the Voice: the Equinox, IV(2). York Beach, Me. : Samuel Weiser.
- ___. (1995). The Book of Lies. York Beach, Me. : S. Weiser.
- ___. (1982). Magick Without Tears. Phoenix, AZ : Falcon Press
- ___. (1996). Little Essays Towards Truth. Tempe, AZ : New Falcon Pub.
- ___. (1982). 777 and other Qabalistic writings of Aleister Crowley. York Beach, Me. : S. Weiser.
- Sabazius. (1995). Pan. Retrieved on Sept. 27, 2004.
- Thelemapedia. (2006). Thelemic mysticism. Retrieved April 21, 2006.
- Thelempedia, the encyclopedia of Thelema and Magick
- The Libri of Aleister Crowley, including Book 4, Magick Without Tears, and others