Charles Spurgeon Commentary Isaiah 44:18

"They know not, neither do they consider: for he hath shut their eyes, that they cannot see; and their hearts, that they cannot understand." — Isaiah 44:18 (ASV)

For he has shut their eyes, that they cannot see; and their hearts, that they cannot understand.

They have been so full of sin that God has given them up to judicial blindness, and hardness of heart has come upon them as a punishment for their rebellion against the Most High.