What does John 12:30 mean?

The gospel of John refers to Jesus' miracles using the Greek term semion, which means "sign." When we see a "sign" by the side of a road, in a hallway, or on the door of a building, we know that there is a message being given. The sign does not exist for its own sake—it's there to tell people something. The evidence Jesus provides during His earthly ministry does the same thing, pointing people to truth (John 20:30–31). Of course, people often ignore signs, for various reasons. They also ignore God's signs.

While speaking to a crowd in Jerusalem (John 12:20–22), Jesus is answered by a voice from heaven (John 12:28). This is as literal and direct a "message from God" as any skeptic could hope for. In fact, some critics of faith often claim that it would take an incident just like this to convince them. That, of course, is not true. Evidence is not the problem, the problem is a spirit that's deliberately stubborn and disbelieving (Romans 1:18–20; John 5:39–40; Luke 16:31). Some of those hearing this voice—in the presence of a man who recently raised the dead (John 11:40–43)—dismiss it as meaningless natural noise (John 11:29).

Jesus' comment here specifically refers to that audible voice from heaven. It also applies, generally, to all the evidence God offers humanity. This message is urgent: each person's time is short (James 4:14), and those who ignore the truth risk being lost for eternity (John 3:16–18). After this encounter, the gospel of John will make it clear that spiritual rebellion is at the heart of disbelief (John 12:37–40).