Most believe it is the “glory” or doxa of God. Thus the idea is not so much the inner attributes of deity as it is the majestic splendor, the unapproachable brilliance and visible token of all that God is in himself (i.e., the Shekinah of God). In the OT the Shekinah was the blinding display of God’s presence among his people. Glory, then, is the majestic radiance of the divine nature. If “form” = radiant display of divine glory, it may be significant that Paul says he was “in (en) the form of God”