DURING THE FIRST two centuries of Christianity, the new religion sustained a constant challenge by the Gnostic movement. This movement was regarded by all Christian authorities as an initial heresy within Christianity itself, but such a view of Gnosticism is clearly inadequate. Gnosticism from its origins constituted a rival religion to both Judaism and Christianity. There were indeed Jewish Gnostics, and a bewildering array of Christian Gnostic sects, but there were also pagan Gnostics. Gnosticism was both a tendency within other religions, and an eclectic but authentic religion in itself.

The basic tenets of Gnosticism have not lost their shock value, their pride of unprecedentedness, even now, in our skeptical era. Yet Gnosticism remains uncanny, in that the shock of its concepts wears off, leaving many of us wondering if Gnosticism is not after all our own religion, whether we know it or not. And yet knowing is the essence of Gnosticism, whose name derives from the Greek word, gnosis , signifying knowledge in an experiential and intuitive sense. The Gnostic is a person who knows that what is oldest and most authentic in him is neither his body nor his soul, but rather is an inmost self, the pneuma or "breath" which is also a "spark" of the fire of an alien, true God, alien both to this cosmos, and to the human body and soul alike. Through no fault of his own the Gnostic finds himself solitary in a cosmic dungeon, our galaxy, cut off from salvation by the true God who has not made this world, has not made man's soul, has not even made the pneuma or man's true self, because that is co-eternal with Him.

The central dilemma of Gnosticism is that it remains a religion of salvation, dependent upon knowing rather than believing, while insisting that salvation is wholly acosmic and atemporal. Pragmatically, Gnosticism is an elitist religion of despair, because it holds out no hope for the natural woman or man, but only an ultimate hope for the "spark" we continue to carry. The central shock of Gnosticism comes from its aggressive side, turned strongly against normative Judaism and orthodox Christianity: The evil or at least foolish Demiurge or wrong-headed god who made the world, our bodies and even our psyches or souls, is no less than Jevoah Elohim, the creative God of the book of Genesis.

Until 1945, when 52 Gnostic texts were discovered in Upper Egypt, most of our actual knowledge of the religion was mediated by the ancient Fathers of the Catholic Church, who wrote extensive works denouncing heresies that they paradoxically preserved through copious extracts.The greatest scholar of Gnosticism was and is the philosopher Hans Jonas, still very much at work, whose wonderful book, The Gnostic Religion (available as a Beacon paperback, $4.95) should be read by anyone who wants an introduction to this compelling world-view. But though the revised and enlarged edition of Jonas' book integrates much of the new material from original sources, it is only now that scholars are able to make full use of what has been so recently revealed. The impressive book under review, The Gnostic Gospels, by Elaine Pagels, an expert upon Gnostic interpretations of New Testament texts, takes as its subject one group of the new sources, a series of non-canonical, heretical gospels that present a Gnostic Jesus, irreconcilable with the Jesus of the four gospels of tradition.

Professor Pagels centers her discussion of the Gnostic gospels upon several problematic areas of contention between orthodox Christianity and Christian Gnosticism. Was the resurrection of Jesus a literal, historical event, as the synoptic gospels insist, or was it a figurative, mythological vision, as the Gnostic gospels suggest? What are the politics of orthodox monotheism as contrasted to the implicit politics of a dualistic religion like Gnosticism? Was there a kind of radical feminist element in Gnosticism, offering God the Mother as an alternative or supplement to the Hebraic Father God? What happens to the early Christian exaltation of martyrdom, when a Gnostic viewpoint is adopted? Finally, what remains of Church organization if the Gnostic emphasis upon a purely intuitive, experiential knowledge of God within is allowed to prevail?

Pagels illuminates all of these problematic questions, and in doing so she provides an effective introduction to the difficult, almost oxymoronic notion of a Christian Gnosticism. She is always readable, always deeply informed, always richly suggestive of pathways her readers may wish to follow out for themselves. Her limitations are deliberate; she is too much the responsible historical scholar of religion to allow herself much speculation or private surmise, as yet. Still, it is the wealth of such surmise, deeply consonant with Gnosticism's freedom of interpretation, that has made most valuable not only the work of Hans Jonas, but also the magnificent labors of Gershom Scholem, the leading scholar of Kabbalah or Jewish Gnosticism, and of the classicist E. R. Dodds, whose Pagan and Christian in an Age of Anxiety (Norton, $3.45) is the book a reader should turn to after Jonas and Scholem.

Pagels ends her book by worrying that the casual reader might assume that she advocates going back to Gnosticism as against orthodox Christianity. Any attentive reader will see that, as she says, it is the history of Christianity that fascinates her most. My own sympathies are very much with Gnosticism, and so I find her final chapter, on "Gnosis: Self-Knowledge as Knowledge of God," her weakest. But, like many other readers, I am indebted to Professor Pagels for her devoted and sound scholarship, and for her clarity of exposition.