How do we know God's will is a mystery?

In Ephesians 1:9, Paul discusses the mystery of God's will, emphasizing that many in the world are unaware of God's active and sovereign control over creation. His will operates in wisdom that ordinary understanding cannot grasp. Until it is revealed by the Holy Spirit, the world remains oblivious to God's intentions and purposes. It's through Scripture and the teaching of the Holy Spirit that believers come to understand and embrace this mystery. Furthermore, God's will encompasses the election of the saints, as indicated in verse 4, demonstrating His particular and sovereign choice in salvation.