How do we know the doctrine of God's eternal purpose is true?

The doctrine of God's eternal purpose, as referenced in Ephesians 3:10, is grounded in the Scriptures which collectively testify to God's redemptive plan through Christ. Paul emphasizes that God's wisdom and purpose were hidden in past ages but are now revealed through the gospel. This makes accessible the understanding that was sought by the prophets and desired by angels. The covenant of grace, as played out in biblical history, illustrates God's sovereign hand at work in fulfilling His purpose, thereby affirming its truth. The continuity of messages regarding Christ from both the Old and New Testaments further substantiates God's eternal purpose as unchanging and reliable.