The pagan world was always haunted by the unknowability of God. At best, men could but grope after his mystery. “It is hard,” said Plato, “to investigate and to find the framer and the father of the universe. And, if one did find him, it would be impossible to express him in terms which all could understand.” Aristotle spoke of God as the supreme cause, by all men dreamed of and by no man known. The ancient world did not doubt that there was a God or gods, but it believed that such gods as there might be were quite unknowable and only occasionally interested in mankind. In a world without Christ, God was a mystery and power, desirable but never known.
Note: The exact quote from Plato is, "Now to discover the Maker and Father of this Universe were a task indeed; and having discovered Him, to declare Him unto all men were a thing impossible." It is from Plato's work: Timaeus, 28 C.