Ephesians 4:18

with their understandings darkened, alienated from the life of God on account of the ignorance which is in them, on account of the hardness of their hearts,

Ephesians 2:12

that at that time you were without Christ, alienated from the polity of Israel, and strangers to the covenants of promise, having no hope and without God in the world;

Galatians 4:8

But formerly, not knowing God you served beings which are not really Gods;

1 Thessalonians 4:5

not with inordinate desires like the gentiles who know not God,

Acts 17:30

Overlooking therefore the times of ignorance, God now commands all men everywhere to change their minds,

Romans 1:21-23

because having known God they glorified him not as God neither were thankful, but became vain in their reasonings and their ignorant mind was darkened.

Romans 11:25

For I wish you not to be ignorant, brothers, of this mystery; that you may not be wise in your own conceit. For hardness in part has come upon Israel, till the fullness of the gentiles shall come in,

Matthew 13:15

for the hearts of this people have become hard, and they hear imperfectly with their ears, and their eyes have they closed, lest they should see with their eyes, and hear with their ears, and understand with their hearts, and turn, and I should heal them.

Mark 3:5

And looking around on them in anger, being grieved at the hardness of their hearts, he said to the man, Stretch out your hand. And he stretched it out, and his hand was restored.

John 12:40

He has blinded their eyes, and hardened their hearts, that they should not see with their eyes and understand with their hearts, and be converted, and I should cure them.

Acts 26:17-18

delivering you from the people, and the gentiles, to whom I send you

Romans 1:28

And as they did not choose to retain God in their knowledge, God gave them up to a reprobate mind, to do things which are not proper,

Romans 2:19

and believe yourself to be a guide of the blind, a light of those in darkness,

Romans 8:7-8

Because the minding of the flesh is enmity against God; for it is not subject to the law of God; for it can not be.

1 Corinthians 1:21

For since, in the wisdom of God, the world by wisdom knew not God, God was pleased by the foolishness of preaching to save those that believe;

2 Corinthians 3:14

but their minds were blinded. For to this day in reading the old covenant the same vail remains, not taken away because it is taken away in Christ;

2 Corinthians 4:4

in whom the god of this life has blinded the minds of the unbelieving, that the light of the gospel of the glory of Christ, who is the likeness of God, may not shine.

Colossians 1:21

And you, formerly alienated and enemies in mind by evil works, he has now reconciled

James 4:4

Adulteresses, know you not that the friendship of the world is enmity against God? Whoever therefore wishes to be a friend of the world, is made an enemy of God.

1 John 2:11

but he that hates his brother is in darkness, and walks in darkness, and knows not where he goes, 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
Overlooking therefore the times of ignorance, God now commands all men everywhere to change their minds,
Acts 26:17
delivering you from the people, and the gentiles, to whom I send you
Romans 1:21
because having known God they glorified him not as God neither were thankful, but became vain in their reasonings and their ignorant mind was darkened.
1 Corinthians 1:21
For since, in the wisdom of God, the world by wisdom knew not God, God was pleased by the foolishness of preaching to save those that believe;
2 Corinthians 4:4
in whom the god of this life has blinded the minds of the unbelieving, that the light of the gospel of the glory of Christ, who is the likeness of God, may not shine.
Galatians 4:8
But formerly, not knowing God you served beings which are not really Gods;
1 Thessalonians 4:5
not with inordinate desires like the gentiles who know not God,

Alienated

Ephesians 2:12
that at that time you were without Christ, alienated from the polity of Israel, and strangers to the covenants of promise, having no hope and without God in the world;
Romans 8:7
Because the minding of the flesh is enmity against God; for it is not subject to the law of God; for it can not be.
Galatians 4:8
But formerly, not knowing God you served beings which are not really Gods;
Colossians 1:21
And you, formerly alienated and enemies in mind by evil works, he has now reconciled
1 Thessalonians 4:5
not with inordinate desires like the gentiles who know not God,
James 4:4
Adulteresses, know you not that the friendship of the world is enmity against God? Whoever therefore wishes to be a friend of the world, is made an enemy of God.

Because

Romans 1:21
because having known God they glorified him not as God neither were thankful, but became vain in their reasonings and their ignorant mind was darkened.
Romans 2:19
and believe yourself to be a guide of the blind, a light of those in darkness,
1 John 2:11
but he that hates his brother is in darkness, and walks in darkness, and knows not where he goes, because the darkness has blinded his eyes.