How do we know that salvation is through Jesus alone?

The necessity of Jesus for salvation is rooted in His unique identity as both fully God and fully man. 1 Timothy 2:5 teaches that Jesus is the one mediator between God and men, which establishes that salvation can be found in no one else. His sacrificial death on the cross and resurrection secured our redemption, as articulated in Romans 5:8, which says that Christ died for us while we were still sinners. Since He bore our sins and fulfilled God's requirement for justice, we are declared righteous before God solely through faith in Him, not by our works or merit.