THE GNOSTIC MOVEMENT
In the first and second centuries of the Common Era numerous schools of thought refer to themselves as "Gnostic." There is no organized religion by the name of "Gnosticism" with specific doctrines to follow and creeds to believe; there are, rather, many different Gnostic systems, each with its own particular theological slant. Several. sects are named after a founder, a specific place, a symbol (like the snake), or a group of people. Four of the most famous fall into the first camp, a school with a particular founder. These are the schools of Marcion, Basilides, Valentinus, and Mani. 
Although each Gnostic sect may emphasize one philosophical point over another, the fundamental aspiration always remains the same: the pursuit of gnosis ; this is the common thread among all the sects. Gnosis, which in Greek simply means knowledge, is not of the intellect, or matters dealing with the everyday world; rather, gnosis refers to knowledge of the spiritual world. The highest form of gnosis would be the knowledge of the Divine--direct, experiential knowledge of God which is not taught or found in the Scriptures. There are really two adjacent forms of knowledge dealing with the spiritual world: knowledge of God (which we shall see is self-knowledge) and knowledge of special techniques, including passwords in order for the soul to ascend through various spiritual regions to the unknown Father.
The underlying goal is to raise one's consciousness beyond the physical world to the higher, spiritual worlds. It is as though the body were a cage in which the soul (as a bird) is entrapped. When the soul vacates the physical body it is said to ascend through various spiritual realms and its consciousness becomes purified. Finally, it reaches its primordial home, the Divine.
According to Gnostics, there is a substratum of reality, an Unknown, Nameless God who is unchanging and immeasurable, transcending any particularity or imposition one can attribute to It. In the Gnostic text The Apocryphon of John this Godhead is referred to as "the invisible One who is above everything," the "unnamable since there is no one prior to him to give him a name," and the "ineffable!' one beyond quantity and quality.  And in Marsanes, God is described as "the Silent One who is not known."  To Marcion, this Unknown Being is the "Alien God," symbolically signifying that the Divine is other to this world/creation.  Each soul or spirit entity is seen as essentially the same essence of God, a pure spark or atom of divine consciousness.
Hence, Gnostics are in some ways advocating a qualified non-dualism in which all souls are ontologically united in the Divine. In other ways, Gnostics are radical dualists, because they make a sharp distinction between the external, physical world and the internal, spiritual world.
The common misnomer is referring to all Gnostics as pessimists who de-value human beings. On the contrary, most Gnostics assign an exceptionally high value to the human soul. The analogy of Plato's cave illustrates this better. According to Plato, the prisoner mistakes shadows on a cave's wall to be reality. But, argues Plato, it is the source of those shadows, the Light, which is the true reality. In the Gnostic view, one has the potential to unshackle the chains of ignorance and turn from the shadows on the wall to look reality straight in the face. The world/creation is seen as evil only because it attracts one to the outside, to the external, and in the process the inner Self is forgotten. This is the great "original sin" according to the Gnostics.
The sleeping spirit is made conscious by the Divine Man or the Redeemer who takes human form. He descends from the spiritual realms to reveal divine secrets and call souls back. Some Gnostics, especially the followers of a Gnostic named Mani,  assume that a Divine Man incarnates in different human forms throughout history to awaken people of all times and places. Accordingly, the Divine Man comes to restore the soul to its original purity and to lead it back to God. Several Gnostics argue that humans return to this earthly realm (reincarnate) until consciousness of the Divine is realized. Again, we see that Gnostics are not de-valuing the human soul but are ultimately suggesting an optimistic fate for it. 
The Gnostic movement as a whole draws upon many mystical philosophies, including neo-Platonism, Judaism, Zoroastrianism, Christianity, and possibly Hinduism,  to name a few. With the spread of a Greek culture, there seems to be a tendency among philosophers to syncretize  waves of thought and to identify a common denominator. 
The Gnostic tradition has often been associated with Christianity. Christian Gnostics claim to have the "true" teachings of Jesus. Many orthodox Christians argue that these esoteric interpretations were absurd and destructive to Christian faith. Nonetheless, in the early second century C.E. these Gnostics were not yet divorced from the greater part of the Christian community. 
Yet, between the third and fourth centuries C.E., the boundaries of Christianity are no longer as fluid, and groups are excluded as heretical. This is the age of the great heresiologists. Irenaeus, the first Church Father, is considered the greatest opponent of the Gnostic tradition. Its five books establish systematic guidelines to reject Gnostics. Several anti-Gnostic writers follow Irenaeus, among which are Hippolytus, Clement, Origen, and Tertullian. In the third and fourth centuries C.E., in an attempt to establish a strong institutionalized Church, extremely sharp boundaries were drawn. The Gnostic movement is accused of trying to undermine the Church, and, consequently, all Gnostic thought is condemned as a heresy. Most Gnostic writings are destroyed at this time.
Despite the apparent historical connection between the Gnostic tradition and Christianity, the argument that the Gnostic tradition emerges from Christianity is tenuous. Contrary to popular understanding, the Gnostic tradition, in its formative stages, seems to have a "parasitical"  relationship with Judaism. Birger Pearson, an expert in Gnostic Studies, suggests that unfulfilled eschatology may have aroused spiritual rebellion in Jewish circles. Consequently, in revolt, a Gnostic hermeneutical program is employed, giving "birth to a radically new religious movement,"  no longer recognizable as Jewish. Thus the Christian Gnostic tradition, argues Pearson, is an attempt on the part of Gnostics to gain entry into Christian communities, or to gain adherents to their communities, by means of equating their own gnosis with alleged secret teachings of Jesus. It is precisely this that causes so much difficulty for modern interpreters, some of whom continue to insist that Gnosticism, in its origins, was sparked by the appearance in history of a suitable savior figure, understood to be Jesus Christ. But this is an illusion. 
Part of the evidence supporting this theory is the Gnostic utilization of the Old Testament. It is interpreted, or more precisely re-interpreted, in a new light. Well-known biblical figures, such as Adam, are given a new role embodying basic Gnostic presuppositions. In a sense, it is a metaphorical teaching device, twisting the original story line to present their ideology. The Sethians, for example, speak of Adam as the figure who) transmits secrets to his son Seth, who then incarnates as "the great illuminator"  (e.g., Melchizedek, Zoroaster, Jesus) to reveal the eternal knowledge to the Gnostic (Sethian) race.  In fact, Gnostics go so far as to reverse the roles of good and evil to present the "deeper meaning." For instance, in the biblical creation story, the serpent (for some Gnostics) is not seen as an evil power but as a positive one, for the serpent urges Eve and Adam to wake up from the slumber and to realize their divine nature. Irenaeus elucidates this Gnostic view:
But their mother (wisdom) cunningly led Eve and Adam astray by the agency of the snake, so that they transgress the commandment of laldabaoth [lower demiurge]. And Eve was easily persuaded, as if she were listening to an offspring of god. And she persuaded Adam to eat from the tree from which god had said not to eat. Moreover--they saw--when they ate they became acquainted with the power which is superior to all, and they revolted from those who had made them. 
The serpent, then, begins to represent something completely different from what it does for the orthodox Jew or Christian. According to Irenaeus, the Gnostic sect of Ophites were among those who utilized this bold allegorization of the serpent in the creation story. 
A prime example of the Gnostic re-interpretation of the Old Testament is their view of the biblical god.  They contend that the god of the Old Testament is penultimate, that is, a lower deity and not the Godhead. They even go as far as to portray him as a demonic being, envious of the human race and striving to enslave souls in ignorance (i.e., through Jewish Law).  We can look at several examples in the Nag Hammadi Codices that describe this illegitimate lower demiurge. For instance, in Trimorphic Protennoia it says of this hostile power:
There appeared the great Demon who rules the lowest part of the underworld and Chaos. He has neither form nor perfection, but on the contrary possesses the form of the glory of those begotten in the darkness. Now he is called "Saklas," that is Samael, "Yaldabaoth," he who had taken power, who had snatched it away from the innocent one (Sophia)... 
Another example is found in The Apocryphon of John which describes an ignorant, jealous god:
He is impious in his arrogance, which is in him. For he said, "I am God and there is no other God besides me," for he is ignorant of his strength, the place from which he had come." 
Since, according to most Gnostics, the creator god is of evil origin, so also is the creation. This anti-cosmic attitude has resulted in varying attitudes of ethics. We learn a great deal about the various Gnostic ethics in Clement of Alexandria's Stromateis (Book III). He writes:
Accordingly we may divide all the heresies into two groups in making answer to them. Either they teach that one ought to live on the principle that it is a matter of indifference whether one does right or wrong, or they set too ascetic a tone and proclaim the necessity of continence on the group of opinions which are godless and arise from hatred of what God has created. 
The ascetics contend that worldly pleasure impedes spiritual growth because it. attracts one to the outside, to the external, and the inner spiritual Self is forgotten. To combat this problem strict ethics are employed. For some, this included a vegetarian diet, extensive fasts, abstinence from intoxicants, and celibacy. Irenaeus places the Gnostic Saturnilus here. He explains:
Marriage and procreation, they maintain, are of Satan. Many of his followers abstain from animated things (i.e., meat), and through this feigned continence they lead many astray. 
According to Clement the Marcionite doctrine of ethics also falls into this camp. He remarks: By the Marcionites nature is regarded as evil because it was created out of evil matter and by a just Creator. On this ground, that they do not wish to fill the world made by the Creator-God, they decide to abstain from marriage. Thus they are in opposition to their Maker and hasten toward him who is called the good God, but not to the God, as they say, of the other kind ... they are continent, not of their own free choice, but from the hatred of the Creator.  He later adds:
Marcionites have interpreted them [children] in a godless sense and are ungrateful to their Creator. 
On the other hand, libertines, like the Barbeliotes, supposedly engage in sexual cultic rituals, which begins with a feast of meat and wine and ends in an orgy. They justify their behavior as a means to transmit their sexual emission and the soul of the dead animal to the heavenly world. They are said to refuse giving birth to children because it again entraps a "seed of light" into an evil creation.  Nature is abused in the worst of ways as a fight against the creator god. Clement is especially infuriated with the "blasphemous immortality of Carpocrates"  who "can have pigs and goats as their associates." 
There is also a third Gnostic group, the moderate ascetics, that Clement fails to categorize. We find here the Valentinians.  Abuse of materials is abandoned; instead,. the materials of the world are used with caution and limitation. Marriage and procreation are also rightfully condoned. The overall theme here is living a life of moderation as, well as indifference to worldly pleasure, but certainly not an aversion or sanctification of it. When Clement is rebuffing encratic behavior of the libertines, he draws upon the Valentinians as a potential model: 
If these people (i.e., the libertines) spoke of acts of spiritual union like the Valentinians, perhaps one could accept their view. But to suppose that the holy prophets spoke of carnal and wanton intercourse is the way of a man who has renounced salvation. 
Indeed, the Gnostic tradition is a complex religious tradition with many fascinating dimensions. Their theology entails a Transcendent God far surpassing the creator god who rules over this earthly plane. The human soul, a microcosm of this highest Being, remains imprisoned in the body since it is fooled by the inferior power and fails to realize its higher nature. The cosmos is viewed as a dark prison and this results in different attitudes of ethics, including asceticism, moderate asceticism, or libertinism The overall objective of the Gnostic is to return to the Unknown God by awakening the human spiritual consciousness. But how does one awaken one's human spiritual consciousness? To answer this question we shall utilize the Nag Hammadi literature. But let us look at a comparable religious tradition known as the Sant tradition.
1. The first three are Christocentric, influenced by the Gospel of John and the letters of Paul; Mani is mostly influenced by Asian philosophy. Some argue Marcion is not a Gnostic because he did not accept the Gnostic tenet that souls are divine by nature or that it is gnosis that saves. Rather, he adopts the Pauline view that one is essentially corrupt and saved only through faith. For further discussion of Marcion, see Kurt Rudolph, op cit., p. 316.
2. The Greek term gnosis is cognate with Sanskrit jnana. Whether gnosis as such is comparable with jn3na-yoga (the causal path of knowledge), however, is debatable.
3. James M. Robinson (ed.), "The Apocryphon of John H," in The Nag Hammadi Library in English (San Francisco: Harper and Row Publishers, 1988, third edition), p106. Hereafter cited as NHL.
4. Marsanes (X,l), in NHL, p. 463.
5. See Kurt Rudolph, op. cit., p. 62. Marcion and Valentinus apparently were excommunicated from the Roman Church for their philosophical position.
6. Mani's alternative church (i.e., the Manichean tradition) eventually died out in the seventeenth century in China. The three principles stressed were: 1) A Divine Man incarnated in different forms (e.g., Buddha, Jesus); 2) Outward observances like sacraments were totally unnecessary; 3) Evil did not originate from God (the world of Light) but had its own principle source--that is, the world of darkness. It is this world of darkness that overwhelmed archetypal Man, contaminating sparks of Light with material form. Mani's dualism of light and darkness, the realm of good and the realm of evil, seems to be directly influenced by Iranian Zoroastrianism. See Rudolph, op. cit., pp. 334-35.
7. This may not apply to Basilides, who, according to Hippolytus, believes that once God has pulled ready souls back to It a "great unconsciousness" will descend upon the rest of humankind. See H. L. Mansel, D.D., The Gnostic Heresies of the First and Second Centuries (London: AMS Press, 1875), p. 156. Yet, it is important to note that there are two irreconcilable accounts of the doctrines of Basilides: one is presented by Hippolytus and the other by Irenaeus. Which account renders a more accurate depiction of Basilides remains uncertain at this time.
8. For an interesting discussion on the philosophical connection between Gnostic ideas and Hindu thought see Geo Widengren, The Gnostic Attitude (Santa Barbara: Institute of Religious Studies, 1973).
9. I hesitate to describe the Gnostic tradition as a syncretistic religion. This label, although a seemingly neutral description, is often coupled with pejorative connotations, generally suggesting that the tradition is simply a subgroup which defiled its parent religion(s).
10. Today, we see this same spirit in the New Age Movement which tries to syncretize religions of the East and West, transpersonal psychology, and modem physics.
11. There is some indication that Gnostic ideas affect many of the writings of the New Testament (especially the Gospel of John). A debatable example is Colossians, which appears to deal with the problem of false teachers and reacts against varying concepts of the soteriology of the soul. Rules of food and drink and ascetical principles, often observances of Gnostics, are scoffed at. Moreover, 2 Thessalonians is in part written in reaction against advocates of a newly emerging philosophy, which, in this letter, are condemned as the lawless one, those "who exalt himself above every so-called god and object of worship, so as to seat himself in the Temple of God, claiming that he is god." Ephesians also warns against "teaching arising from human trickery," but this letter incorporates several attitudes similar to Gnostics. It discusses Jesus' descent from the inner regions and petitions the "Sleeper to Awake and arise from the dead." The letter of Jude, the second letter of Peter, and the Pastoral letters (1 Timothy, 2 Timothy, Titus) clearly attack false teachers who make reference to "what is falsely called knowledge." Several scholars suggest, however, that during the composition of the New Testament the Gnostic tradition was at such an early stage of development that the writers may have been reacting to another tradition other than the Gnostic tradition.
12. Pearson, op. cit., p. 8.
13. Ibid., p. 125. For further discussion of the relationship between Judaism and the development of the Gnostic tradition see chapter three of Pearson's book, pp. 39-51.
14. Ibid., p. 9.
15. The Apolcalypse of Adam (V. 5), in NHL, p. 285.
16. For an insightful analysis of Seth, see Pearson, op. cit., pp. 52-83.
17. Irenaeus, Adversus Haereses, I.30.8; I.30.9; I.30.15. Hereafter cited as Adv. haer.
18. Irenaeus, Adv. haer., I.30.7.
19. God spelled with a lower case 'g' is not meant to be disrespectful in any way to the Judaic/Christian religion. It represents the Gnostic understanding of an inferior demiurge, while God with an upper case 'G' refers to the Gnostic Transcendent God.
20. The three Christian Gnostics (Marcion, Basilides and Valentinus) supported this theology, and both Marcion and Valentinus were excommunicated from the Roman Church for their philosophical position.
21. Trimorphic Protennoia (XHI,I), in NHL, p. 515.
22. The Apocryphon of john, in NHL, p. 111.
23. Henry Chadwick, B.D. and John Ernest Leonard, D.D., translators, "Stromata" (Bk. IIII), The Library of Christian Classics Vol. II. Alexandrian Christianity (Philadelphia: The Westminister Press), p. 58.
24. Irenaeus, Adv. haer., 1.24.2.
25. Stromata, Bk. III, p. 46.
26. Ibid., p. 50.
27. Epiphanius, Pararion, 26.9.4.
28. Stromata, Bk. III, p. 52.
29. Ibid., p. 53.
30. James E. Davidson, "Structural Similarities and Dissimilarities in the Thought of Clement of Alexandria and the Valentinians," The Second Century: A Journal of Early Christian Studies, Vol. III, No. IV (Georgia: Mercer University Press, Winter 1983), pp. 214-15.
31. Clement's own ethics clearly fall into this third camp. He takes the motto, "It is better to marry than to bum." See Stromata, Bk. III, p. 53. "Burning" here simply means desire and suppression of such only intensifies it. Celibacy is acceptable if "chosen according to sound rule with godly reasons, provided that the person gives thanks for the grace God has granted, and does not hate the creation or reckon married people to be of no account." (p. 85) He continues to add that "both celibacy and marriage have their own different forms of service and ministry to the Lord." (p. 90) In regards to dietary ethics, Clement again stands in the moderate camp. Ideally, he promotes a meatless, alcohol free diet, but, according to Clement, "if one partakes of them, he does not sin." See Stromata, Bk. VII, p. 532..
32. Stromata, Bk. III, p. 53.