Ephesians 4:18

being darkened in their understanding, alienated from the life of God because of the ignorance that is in them, because of the hardness of their hearts;

Ephesians 2:12

that at that time ye were apart from Christ, alienated from the commonwealth of Israel, and strangers to the covenants of promise, having no hope, and without God in the world.

Galatians 4:8

But then, indeed, when ye knew not God, ye served those which by nature are no gods;

1 Thessalonians 4:5

not in passion of desire, even as the gentiles, who know not God;

Acts 17:30

God, therefore, having overlooked the time of ignorance, now commands all men everywhere to repent;

Romans 1:21-23

because, having known God, they did not glorify Him as God, nor did they give thanks; but they became vain in their reasonings, and their senseless heart was darkened.

Romans 11:25

For I do not wish you, brethren, to be ignorant of this mystery (lest ye be wise in your own conceits), that a hardening, in part, has befallen Israel, until the fulness of the gentiles come in;

Matthew 13:15

for the heart of this people was made gross, and with their ears they heard heavily, and their eyes they closed; lest they should see with their eyes, and hear with their ears, and understand with their heart, and turn, and I should heal them.'

Mark 3:5

And having looked round about on them with anger, and being grieved at the hardness of their heart, He saith to the man, "Stretch forth your hand." And he stretched it forth; and his hand was restored.

John 12:40

"He hath blinded their eyes, and He hardened their heart, lest they should see with their eyes, and understand with their heart, and turn, and I should heal 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 approve the holding of God in their knowledge, God delivered them up to a reprobate mind, to do those things which are not becoming;

Romans 2:19

and have become confident that you are a guide of the blind, a light to those in darkness,

Romans 8:7-8

because the mind of the flesh is enmity against God; for it is not subject to the law of God, neither, indeed, can it be;

1 Corinthians 1:21

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

2 Corinthians 3:14

But their minds were unimpressible; for until this day upon the reading of the old covenant the same veil remains unlifted; which in Christ is done away.

2 Corinthians 4:4

in whom the god of this world blinded the minds of the unbelieving, that the light of the Gospel of the glory of Christ, Who is the image of God, should not shine upon them.

Colossians 1:21

And you, being in time past alienated and enemies in your mind in evil works,

James 4:4

Adulteresses! know ye not that the friendship of the world is enmity with God? Whosoever, therefore, purposes to be a friend of the world makes himself an enemy of God.

1 John 2:11

But he that hates his brother is in the darkness, and walks in the darkness, and knows not where he is going, because the darkness 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
God, therefore, having overlooked the time of ignorance, now commands all men everywhere to repent;
Acts 26:17
delivering you from the people and the gentiles, to whom I send you,
Romans 1:21
because, having known God, they did not glorify Him as God, nor did they give thanks; but they became vain in their reasonings, and their senseless heart was darkened.
1 Corinthians 1:21
For, since in the wisdom of God, the world through its wisdom knew not God, God was pleased through the foolishness of preaching to save those who believe;
2 Corinthians 4:4
in whom the god of this world blinded the minds of the unbelieving, that the light of the Gospel of the glory of Christ, Who is the image of God, should not shine upon them.
Galatians 4:8
But then, indeed, when ye knew not God, ye served those which by nature are no gods;
1 Thessalonians 4:5
not in passion of desire, even as the gentiles, who know not God;

Alienated

Ephesians 2:12
that at that time ye were apart from Christ, alienated from the commonwealth of Israel, and strangers to the covenants of promise, having no hope, and without God in the world.
Romans 8:7
because the mind of the flesh is enmity against God; for it is not subject to the law of God, neither, indeed, can it be;
Galatians 4:8
But then, indeed, when ye knew not God, ye served those which by nature are no gods;
Colossians 1:21
And you, being in time past alienated and enemies in your mind in evil works,
1 Thessalonians 4:5
not in passion of desire, even as the gentiles, who know not God;
James 4:4
Adulteresses! know ye not that the friendship of the world is enmity with God? Whosoever, therefore, purposes to be a friend of the world makes himself an enemy of God.

Because

Romans 1:21
because, having known God, they did not glorify Him as God, nor did they give thanks; but they became vain in their reasonings, and their senseless heart was darkened.
Romans 2:19
and have become confident that you are a guide of the blind, a light to those in darkness,
1 John 2:11
But he that hates his brother is in the darkness, and walks in the darkness, and knows not where he is going, because the darkness blinded his eyes.