How do we know that Christ's sufficiency is true?

The sufficiency of Christ is attested throughout Scripture, where God's promises and character assure us of His adequacy. The narratives in the Old Testament, particularly in the book of Judges, illustrate humanity's inclination to forsake the true God for false idols when they perceive God to be insufficient. However, the New Testament repeatedly affirms Christ’s all-sufficiency, notably through His statements and teachings. For example, in John 14:6, Jesus proclaims, 'I am the way, the truth, and the life; no man cometh unto the Father, but by me.' Furthermore, the historical faithfulness of God, as seen through the experiences of believers, validates the truth of this doctrine. The remnant of faithful believers throughout history has consistently witnessed God’s all-sufficient grace in their lives, further establishing the reality of this foundational truth.