How do we know the doctrine of Christ and Him crucified is true?

The truth of the doctrine of Christ and Him crucified is affirmed by the resurrection, which serves as God's validation of Christ's work on the cross. According to 1 Corinthians 15:17, if Christ is not raised, our faith is futile. However, God raised Him from the dead, demonstrating that He accepted Christ's sacrifice as a complete atonement for sin. This resurrection assures us that God's promises to save His people will certainly come to pass. Therefore, this doctrine is not merely theological speculation but is grounded in the historical reality of the resurrection.