What does John 12:45 mean?

These words are not tied to any particular place or time, so we cannot be sure if they're a single speech, or a summary of Jesus' message in the days leading up to His arrest and crucifixion. Either way, this passage explains the final lesson given by Christ in those hours prior to His departure from the public view.

Scripture makes it clear that Jesus Christ is God; He is identical to God the Father. Here, the emphasis is on the idea that when one sees or hears from Jesus, they are also seeing and hearing God. This is why a rejection of Christ is a rejection of God (John 3:18, 36). Though people cannot see a visible form of God the Father, they can see God visibly in the form of the Son (Colossians 1:15). Those who do not see Christ for what He is are those "blinded" to the truth (2 Corinthians 4:4). This condition is one a person can bring on himself as judgment for stubborn disbelief (John 12:37–43).

As Jesus will explain to the disciples (John 14:9–10), Christ is the manifestation of God in human form. There is no other possible option for salvation (John 14:6), and no other way to be reconciled to God (Acts 4:12).