The central theme of the sermon is exploring and affirming the identity of believers in Christ Jesus, drawing from Jeremiah 29:11 and various other scriptures. The speaker emphasizes that true identity comes not from our roles or past labels, but from who God declares us to be. The message is structured around four fundamental truths about a believer's identity: being a child of God, being forgiven and free, being God's workmanship, and being made brand new in Christ. Each point highlights the importance of recognizing these truths to combat negative self-perceptions and external judgments.