Brethren, be not children in understanding: howbeit in malice be ye children, but in understanding be men. 1 Corinthians 14:20
"The wise man wrote long ago, “With all thy getting get understanding” (Proverbs 4:7).
However, we need to be sure that the understanding we acquire is not
perverted by the spirit of this world.
When Paul wrote to the Ephesians,
he emphasized the contrast 
between a darkened understanding and a
spiritually illuminated understanding.
“Walk not as other Gentiles walk,” he exhorted, “in the vanity of their
mind, 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” (Ephesians 4:17-18).
A blinded heart produces a darkened understanding."
HMM