Why Augustine called man as a great mystery?

Augustine referred to man as a great mystery due to the complex interplay of the human soul, intellect, and will, which reflects both divine creation and the struggle with sin. He believed that understanding humanity involves grappling with profound questions about existence, purpose, and the relationship with God. This mystery encompasses the duality of being created in God's image yet falling short of divine ideals. Ultimately, Augustine saw this complexity as a journey toward spiritual truth and self-discovery.