How do we know the doctrine of complete salvation is true?

The doctrine of complete salvation is grounded in the truth of scripture, showcasing how God has meticulously provided for our salvation through Jesus Christ from the foundation of the world. In Isaiah 4:2, the 'branch of the Lord' is described as beautiful and glorious, representing Christ as the source of true salvation. The New Testament reaffirms this by stating in 2 Thessalonians 2:13 that God has chosen His people for salvation through the Spirit's sanctification. The fulfillment of this promise is found in the completed work of Christ on the cross, as stated in Romans 8:32-34, guaranteeing that our salvation is secure and unalterable due to Christ’s righteousness.