Spiritual theologian Eugene Peterson:
A metaphor states as true something that is literally not true. For instance, “God is a rock,” a frequent Hebrew assertion about God (“The LORD is my rock. . . . [W]ho is a rock, except our God?” Ps. 18:2, 31). If we take the sentence literally, instead of going to church on Sunday mornings to worship we will visit the local stone quarry and shop for a god rock that we can erect in our backyard. The alternative is to dismiss the sentence as meaningless, which would leave us with a Bible with every other sentence or so deleted, including some of our most prized: the Lord is my shepherd (Ps. 23:1); the Lord is a warrior (Exod. 15:3); I am a rose of Sharon (Song 2:1); I am the true vine (John 15:1).
Sandra Schneiders expertly characterizes metaphor as language that “contains an ‘is’ and an ‘is not,’ held in irresolvable tension.” The tension is inherently uncomfortable and administers a kind of shock treatment to the mind, stimulating it to a deeper understanding than what can be accounted for by a literal surface reading. If we suppress the “is” we kill the metaphor and end up with a mummified corpse of its meaning. If we suppress the “is not” we literalize the metaphor and end up with a junkyard of wrecked and rusted-out words.
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For one thing, God’s action and presence among us is so beyond our comprehension that sober description and accurate definition are no longer functional. The levels of reality here are so beyond us that they compel extravagance of language. But the language, though extravagant, is not exaggerated. All language, but especially language that deals with transcendence, with God, is inadequate and falls short.
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A metaphor is a word that bears a meaning beyond its naming function; the “beyond” extends and brightens our comprehension rather than confusing it. Just as the language of ecology demonstrates the interconnectedness of all things (air, water, soil, persons, birds, and so forth), the language of metaphor demonstrates the interconnectedness of all words.
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Metaphor does not explain; it does not define; it draws us away from being outsiders into being insiders, involved with all reality spoken into being by God’s word. . . . Metaphor sends out tentacles of connectedness. As we find ourselves in the tumble and tangle of metaphors in Scripture we realize that we not schoolboys and schoolgirls reading about God, gathering information or “doctrine” that we can study and use; we are residents in a home interpenetrated by spirit – God’s Spirit, my spirit, your spirit. The metaphor makes us part of what we know.
–– Eat This Book: A Conversation in the Art of Spiritual Reading (pp. 94-98)