“Teachers of religion have always attempted to raise their insights to the level of utterance, dogma, creed. Yet such utterances must be taken as indications, as attempts to convey what cannot be adequately expressed, if they are not to stand in the way of authentic faith.” 
I take what Rabbi Heschel is saying here about “authentic faith” as meaning that too much confidence placed in what one knows ABOUT God can distance one from actually knowing God.
Augustine of Hippo defined the Latin equivalent, theologia, as “reasoning or discussion concerning the Deity.” It is now, more or less, probably best defined as the systematic and rational study of concepts of God. But isn’t this a kind of oxymoron? Can there ever be a rational understanding, a “science” of God? Rabbi Heschel seems quite clear on this point:
“What are grounds for our certainty of the realness of God? It is clear that we cannot submit religion to scientific logic. Science is not the only way to truth, and its method do not represent all of human thinking. Indeed, they are out of place in that dimension of human existence in which God is a burning issue… God is not a scientific problem, and scientific methods are not capable of solving it.”
We of the Western Christian faith are steeped in theology; we seem to have all but come to believe in the concept that God can somehow be qualified and quantified as a system of conjoined theological deductions. But does this clarify or distort our understanding of Him; does it draw us nearer to or cut us off from a deeper intimacy with God, like an altogether too-thick layer of winter clothing would keep us from feeling a warm ocean breeze as we walk along the beach of a tropical island?
As Rabbi Heschel writes: “The moment we utter the name of God we leave the level of scientific thinking and enter the realm of the ineffable.”
How does one quantify and qualify “the ineffable?”
 Abraham Joshua Heschel, “God in Search of Man: A Philosophy of Judaism”
 City of God Book VIII. i.
 Heschel, “God in Search of Man: A Philosophy of Judaism”