# God has given them a spirit of dullness, eyes so that they should not see, and ears so that they should not hear

They are not able to hear or receive spiritual truth. (see Deuteronomy 29:4)

# spirit of

Here this means "having the characteristics of," such as the "spirit of wisdom."

# eyes so that they should not see

The concept of seeing with one's eyes was considered to be equivalent to gaining understanding.

# ears so that they should not hear

The concept of hearing with the ears was considered to be equivalent to obedience.