When we think of the term “mystery” we generally believe it is something to be solved. When we read a Sherlock Holmes novel we expect to learn by the end of the novel “who did it,” and the clues that led Holmes to use his extraordinary deductive reasoning capabilities to discover the culprit. We usually do not like mysteries without endings, nor stories that do not tie up the loose ends.
When we speak of God as Ultimate Mystery, we mean something different. We can never experience the fullness or completeness of God who is eternal. God is beyond our finite ability to comprehend or describe. At best, we can only say what God is not and not what God is.
Given the eternal and transcendental attributes ascribed to God, and our own creaturely finiteness, we can never directly know nor experience the full and complete depth and breadth of God. At best, we are able to only experience a limited, partial unveiling of God that God chooses to reveal to us.
The Christian faith tradition teaches that God can be experienced through what God has created. If God is Ultimate Love, Ultimate Truth, Ultimate Goodness, and Ultimate Beauty, then we can also experience the Presence of the Godself whenever or wherever we experience love, truth, goodness, and beauty. God also speaks to us through our conscience.
The Christian faith tradition also teaches that God's "Word," the "Second Person" of the Trinity—the "Son of God"—entered into creation through the Incarnation, and is most fully revealed to us through the person of Jesus of Nazareth, the “human face of God” for us. "For the Son of God became [human] so that we might become God" (St. Athanasus, CCC no. 460). The Incarnation is the manifestation of the divine in creation. Can we not also, by our creation and with God's grace, become a manifestation of the divine in our person?