During the early centuries before and after Jesus' time a flood-tide of mystery cults and resurrecting savior myths culminated in and around the Middle East representing rebirth of nature and the seasons, and personal rebirth as well.  (As without, so within.).) 

As Christianity became popular, Jesus' image and teachings moved from being the catalyst for Christians' rebirth in this life to replacing the resurrecting saviors and representing cosmic rebirth as well.  That is why we find Biblical passages like the following:

  "He was in the beginning with God.  All things were made through him and without him nothing was made..."(John 1:1-4)   Again: "In the Christ God created all things in the heavens and on the earth, visible and invisible. Before anything created Christ was."(Col. 1:15)  (See also 2 Cor. 3:18;  Eph.1:9-10;  Heb. 1:3)

Such passages must have inspired Matthew Fox to write The Coming of the Cosmic Christ, echoing Paul and mystics like Meister Eckhart in paralleling Christ's earthly birth and resurrection with his continuing birth and resurrection as Offspring of the Cosmic Godhead: "God the Son".  Just as the Logos becomes flesh in John's Gospel, it now becomes God's cosmic body - the wounded body of the universe - the Cosmic Christos as God's power of resurrection throughout all of creation. 

Here we encounter Christ's two natures.  On the one hand a son of God, on the other - "God the Son" - third "person" of the Trinity.  Just as Jesus represented rebirth as a flesh and blood person on this earth, he now represents resurrection on a cosmic scale after death.  This is a powerful archetypal symbol to tap into.  For as Meister Eckhart once said: "Where would be my salvation if the Christ resurrects throughout all of eternity and does not also resurrect in me."

Does this mean the man, Jesus, is now actually "God the Son"?  Jesus' story and image became the imprinted archetypal catalyst for rebirth, healing, and overcoming for his devout believers.  Regardless of where his physical body has gone, the Christ now represents heavenly resurrection as well.  This latter representation gives his symbol its ultimate power to help and heal his earthly followers.  An Irish Catholic poet captured the image of the Cosmic Christos thusly:

I see his blood upon the rose,

And in the stars his watching eyes.

His body gleams in glacial snows.

His tears fall from the skies.