How do we know the doctrine of new creation in Christ is true?

The doctrine of being a new creation in Christ is grounded in Scripture, particularly in 2 Corinthians 5:17, which states that if anyone is in Christ, they are a new creature. This change is not merely outward; it is a complete transformation upheld by God's Spirit. The transformation signifies a shift from reliance on the flesh to living by faith, resulting in a renewed heart and purpose that aligns with God’s righteousness. This profound spiritual change confirms the truth of the doctrine, as believers experience genuine faith and love for Christ.