How do we know faith in Christ is necessary for salvation?

Faith in Christ is essential for salvation, as established in John 6:40, which states that everyone who sees the Son and believes in Him will have eternal life. This belief is not merely intellectual assent but involves a deep, personal trust in Christ's work on the cross for the forgiveness of sins. Romans 10:14-15 further highlights that one cannot believe in Christ if they have not heard His message, confirming the need for preaching the true gospel. Salvation is exclusively through faith in Christ's obedience and sacrifice, reinforcing that the only way to be justified before God is through trust in Jesus as our Savior. Thus, the doctrine emphasizes that salvation is grounded in faith, highlighting both the necessity of Christ's redemptive work and the individual's response of belief.