Ephesians 4:18

having their understanding darkened, alienated from the life of God through the ignorance that is in them, because of the hardening of their hearts.

Ephesians 2:12

were once upon a time without Christ, aliens from the commonwealth of Israel, strangers to the covenants of the Promise, without hope and without God in the world.

Galatians 4:8

But once, when you Gentiles had no knowledge of God, you were slaves to gods which have no real being.

1 Thessalonians 4:5

Not in the passion of lust, like the Gentiles who know not God.

Acts 17:30

"The times of ignorance God overlooked, but he now commands all men that they should all, everywhere, repent;

Romans 1:21-23

For although they knew God, yet they did not glorify him as God, nor give him thanks; but became vain in their reasoning, and their senseless minds were darkened.

Romans 11:25

For I would not, my brothers, have you ignorant of this hidden truth, for fear that you become wise in your own conceits. that a hardening in part has befallen Israel, until the fulness of the Gentiles is come in.

Matthew 13:15

For the heart of his people is made fat, Their ears are dull of hearing; Their eyes, too, have they closed, Lest some day their eyes should perceive, And their ears should hear, And their heart should understand and turn, And I should heal them.

Mark 3:5

They were silent. Then looking around upon them with anger, and deeply grieved by the hardening of their hearts, he said to the man, "Stretch out your hand!" He stretched it out, and the hand was at once completely restored.

John 12:40

He hath blinded their eyes and make their hearts hard, Lest they should see with their eyes, perceive with their minds, And should turn, and I should heal them.

Acts 26:17-18

"'I will deliver you from the Jewish people, and from the Gentiles to whom I am sending you to open their eyes

Romans 1:28

And just as they refused to continue to retain God in their knowledge, so did God cast them out to an outcast mind, to do those things which were indecent.

Romans 2:19

and are confident that you yourself are a darkness,

Romans 8:7-8

For to be earthly minded is enmity against God; For such a mind is not subject to the Law of God, Nor can it be;

1 Corinthians 1:21

For when, in the wisdom of God, the world by its philosophy knew not God, the world by its philosophy knew not God, it pleased God, by the foolishness of preaching, to save those who believe.

2 Corinthians 3:14

Nay, their minds were made dull; for to this very day, at the public reading of the Old Testament, the same veil rests thereon, because it is not revealed to them that in Christ the veil is taken away.

2 Corinthians 4:4

Among them the god of this age has blinded the understanding of the unbelieving so that the sunshine of the gospel of God, should not dawn upon them.

Colossians 1:21

And you, alienated as you once were, hostile at heart in your evil deeds,

James 4:4

You adulteresses, do you not know that the friendship of the world is enmity to God? Whoever, then, desires to be a friend of the world, makes himself and enemy of God.

1 John 2:11

But he who hates his brother is in the darkness, and is spending his life in the darkness, and does not know where he is going, because the darkness has blinded his eyes.

Treasury of Scripture Knowledge

Summary

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:

Bible References

The understanding

Acts 17:30
"The times of ignorance God overlooked, but he now commands all men that they should all, everywhere, repent;
Acts 26:17
"'I will deliver you from the Jewish people, and from the Gentiles to whom I am sending you to open their eyes
Romans 1:21
For although they knew God, yet they did not glorify him as God, nor give him thanks; but became vain in their reasoning, and their senseless minds were darkened.
1 Corinthians 1:21
For when, in the wisdom of God, the world by its philosophy knew not God, the world by its philosophy knew not God, it pleased God, by the foolishness of preaching, to save those who believe.
2 Corinthians 4:4
Among them the god of this age has blinded the understanding of the unbelieving so that the sunshine of the gospel of God, should not dawn upon them.
Galatians 4:8
But once, when you Gentiles had no knowledge of God, you were slaves to gods which have no real being.
1 Thessalonians 4:5
Not in the passion of lust, like the Gentiles who know not God.

Alienated

Ephesians 2:12
were once upon a time without Christ, aliens from the commonwealth of Israel, strangers to the covenants of the Promise, without hope and without God in the world.
Romans 8:7
For to be earthly minded is enmity against God; For such a mind is not subject to the Law of God, Nor can it be;
Galatians 4:8
But once, when you Gentiles had no knowledge of God, you were slaves to gods which have no real being.
Colossians 1:21
And you, alienated as you once were, hostile at heart in your evil deeds,
1 Thessalonians 4:5
Not in the passion of lust, like the Gentiles who know not God.
James 4:4
You adulteresses, do you not know that the friendship of the world is enmity to God? Whoever, then, desires to be a friend of the world, makes himself and enemy of God.

Because

Romans 1:21
For although they knew God, yet they did not glorify him as God, nor give him thanks; but became vain in their reasoning, and their senseless minds were darkened.
Romans 2:19
and are confident that you yourself are a darkness,
1 John 2:11
But he who hates his brother is in the darkness, and is spending his life in the darkness, and does not know where he is going, because the darkness has blinded his eyes.