“No one has heard or perceived by the ear, no eye has seen a God beside you, who acts for those who wait for him” —Isaiah 64:4
This ‘not hearing’ and ‘not seeing’ highlights the uniqueness of God. It implies that we have heard of him and that we have seen him. God has revealed himself to us. And yet his understanding is unsearchable.
Herman Bavinck on God’s incomprehensibility and knowability:
Religion and the knowledge of God can have their origin only in revelation. If God does not reveal himself in his creatures, knowledge of him is evidently unattainable. . . It is even impossible for God fully to reveal himself to and in his creatures, for the finite does not grasp the infinite. . . Moreover, that which God reveals of himself in and through creatures is so rich and so deep that it can never be fully known by any human individual. In many respects we do not even understand the universe of created beings, which again and again confronts us with enigmas and mysteries. How then should we be able to understand the revelation of God in all its riches and depth?
By admitting this we by no means deny God’s knowability. God’s incomprehensibility, instead of abrogating his knowability, presupposes and affirms the same. The unsearchable riches of the Divine Being constitutes a necessary and important element of our knowledge of God.
The Doctrine of God, p. 41-42.