The mystics were a different breed from the theologians. They emphasized negative theology, the via negativa -- God is not this, God is not that. By and large, they rejected all metaphors for God, including the personal metaphor so dear to orthodox theologians. The God of the mystics is the intuited mystery that is implicit in the creation, the mystery that becomes ever more manifest the more we know about reality -- what Nicholas of Cusa called "learned ignorance." Of God, all negations are true, said Cusa, and all affirmations are inadequate: "Sacred ignorance has taught us that God is ineffable."
The God of the mystics is the Deus absconditus, the absconded God, of whom every metaphor is inadequate, including, of course, the metaphor "whom." The language of the mystics is poetry, not theology; it springs from the sense that there is more to reality than meets the eye, more than we can immediately -- perhaps ever -- know by scientific investigation. We know today vastly more about the universe than did the great spiritual thinkers of an earlier time, and our language of celebration is correspondingly different, but we can learn from them the dimensions of our ignorance, and praise with them the intuited mystery for which even the word God is a diminishment.
The religious naturalist accepts the intuition of mystery as part of what it means to be human, but refuses to put a name to it, or especially a human characteristic -- personhood, love, justice, anger, or artifice. In this, we are not so different from the medieval mystics. John of the Cross never failed to emphasize the hiddenness -- the unknowability -- of God:
Where have you hidden away,
lover, and left me grieving, care on care?
...imploring the empty air.
No sign for me to mark,
no other light, no guide
except for my heart --
the fire, the fire inside.
Or Meister Eckhart: "That which one says is God, he is not; that which one does not say, he is more truly that."
Most contemporary scientists and the mystics agree: We are profoundly ignorant of the Incomprehensible Cause that has from the dawn of human consciousness been an enduring source of religious feeling. We are stalkers, instruments of the hunt, in Annie Dillard's phrase. Something is going on and we want to be part of it. What exactly is going on remains deep beyond our knowing, now, and perhaps forever. We stalk, we seek, for glimmers of the absolute by paying attention to the natural world as it is, the only reliable revelation.