In her book Christ the Key, Kathryn Tanner uses the same metaphor in describing how human nature "strongly images" God by participating in the divine life:
In virtue of such close attachment to the divine image, humans would be the image of God, not just in leading borrowed lives, but by living off God, so to speak, by drawing their very life, that is, from the divine image to which they cling, in something like the way an unborn baby lives off the life of its mother, living in, with, and through her very life. Or--to use the more common biblical imagery perhaps--they would exist as images by being like branches living only off the alien sap of the vine to which they have been grafted. They would be images in the way otherwise empty mirrors enjoy brightness only by receiving outside themselves the light of another.
