There is a difference between knowing information and knowing a Person.
Paul draws a hard line.
Ephesians 4:17
This I say therefore, and testify in the Lord, that ye henceforth walk not as other Gentiles walk, in the vanity of their mind.
Vanity of mind. Empty thinking. A life built on fog.
The problem is not lack of intelligence. It is misplaced direction. A sharp mind pointed at self becomes hollow.
David once prayed for a clean heart because he knew he could not create one. But he could change his mind. When the mind turns, the heart follows.
If I stop excusing what God calls sin, something shifts. If I stop defending the habit and call it what it is, heaven meets me there.
God changes hearts.
We change minds.
Ephesians 4:18
Having the understanding darkened, being alienated from the life of God through the ignorance that is in them, because of the blindness of their heart.
Darkened understanding does not start in the head. It starts in the heart.
When worship drifts from God to self, blindness follows. Romans 1 describes people claiming wisdom while drifting further into foolishness. It is possible to sound enlightened and be spiritually dim.
Then comes something more frightening.
Ephesians 4:19
Who being past feeling have given themselves over unto lasciviousness, to work all uncleanness with greediness.
Past feeling.
Sin always promises excitement. It eventually produces numbness.
Imagine dropping an eight hundred pound weight onto a body with no pulse. There is no reaction. Not because the weight is light. Because the body is lifeless.
When sin does not feel heavy anymore, it is not strength. It is death.
But Paul refuses to leave us there.
Ephesians 4:20–21
But ye have not so learned Christ;
If so be that ye have heard him, and have been taught by him, as the truth is in Jesus.
Notice what he says. Not that you have learned about Christ.
You have learned Christ.
You can study a historical figure and master facts. You can quote speeches and recite timelines. That does not mean you know him.
Learning Christ is different.
It is opening the Gospel and saying, “That convicts me.”
“That exposes me.”
“That comforts me.”
“That confuses me.”
It is reading a verse and talking back.
It is turning information into communion.
Information fills the mind.
Communion awakens the heart.
And when you learn Christ, vanity drains away. Blindness lifts. Feeling returns.
Not because you mastered theology.
Because you met Him.