My Notes
What Does John 12:39 Mean?
"Therefore they could not believe, because that Esaias said again." John makes a disturbing assertion: they could not believe. Not wouldn't — could not. And the reason given is Isaiah's prophecy (Isaiah 6:10): God has blinded their eyes and hardened their hearts. The inability to believe is attributed to prophetic fulfillment.
The theological difficulty is acute: did God prevent belief? Did Isaiah's prophecy cause the blindness? John presents the relationship as fulfillment, not causation: Isaiah said this would happen, and it did. The prophecy described a condition that was already developing; it didn't create the condition.
The verb "could not" (ouk edynanto) describes inability — a structural incapacity rather than a volitional refusal. Something had happened to their capacity to believe. Whether the hardening was judicial (God's response to persistent rejection) or natural (the cumulative effect of refusing truth), the result is the same: they could not believe.
Reflection Questions
- 1.Does the possibility of losing the ability to believe create urgency in your spiritual life?
- 2.How does persistent rejection of truth gradually erode the capacity for faith?
- 3.What's the difference between 'would not' and 'could not' believe — and which describes you?
- 4.If you can still believe right now, what are you waiting for?
Devotional
They could not believe. Not wouldn't. Could not. Their capacity to believe had been structurally compromised. The ability itself was gone.
This is one of the most terrifying verses in John's Gospel because it describes a condition most people don't think is possible: the loss of the ability to believe. Not the refusal to believe — the inability. Something has happened to these people that makes faith structurally impossible.
John connects this to Isaiah's prophecy about eyes blinded and hearts hardened. The connection is fulfillment, not causation in the simplistic sense. Isaiah didn't make them blind by predicting their blindness. He described a trajectory that was already in motion. And when the trajectory reached its conclusion, the people at the end of it could not believe — even with the evidence standing in front of them.
The hardening is cumulative. You don't lose the ability to believe overnight. You lose it through persistent, repeated rejection of truth. Each refusal hardens the heart slightly. Each dismissal dims the eyes incrementally. Over time — over decades, over generations — the cumulative effect produces structural inability. The heart that refused to believe for long enough eventually cannot believe.
This should produce urgency, not fatalism. The ability to believe isn't guaranteed permanently. It can erode. It can diminish. It can, eventually, disappear. If you can still believe — if the capacity is still there — use it. Because the trajectory toward could-not is gradual, and the endpoint is irreversible.
Can you still believe? Then believe now. Before the could-not arrives.
Commentary
Trusted original commentary from respected historical Bible scholars and theologians.
He hath blinded their eyes, and hardened their heart,.... It is of no great moment, whether the he, who is said to blind…
They could not believe - See Mar 6:5; “He could there do no mighty works,” etc. The works can and could are often used…
Therefore they could not believe - Why? Because they did not believe the report of the prophets concerning Christ;…
We have here the honour done to our Lord Jesus by the Old Testament prophets, who foretold and lamented the infidelity…
Therefore Or, For this cause (Joh 12:12; Joh 12:12); see on Joh 7:21-22. It refers to what precedes, and the -because"…
Cross References
Related passages throughout Scripture