In just 30 short words, Romans 1.21 has so much to say, and none of it is lovely.
People knew God through His out-of-this-world creation!
But they chose to not honor Him.
They figured it unnecessary to thank Him.
Consequently, their hearts were dark and foolish.
And their thinking—they just came up with some very weird ideas. Paul says that their thinking became futile.
"For although they knew God, they did not honor Him as God or give thanks to Him, but they became futile in their thinking, and their foolish hearts were darkened."
That’s really unfortunate, because thinking can be a rather good asset.
Fast-forward to Romans 12:1-2. We are told,
“I urge you, brothers and sisters, in view of God’s mercy, to offer your bodies as a living sacrifice, holy and pleasing to God—this is your true and proper worship. Do not conform to the pattern of this world, but be transformed by the renewing of your mind. Then you will be able to test and approve what God’s will is—His good, pleasing and perfect will.”
Do you catch the connection? Denial of God will darken your mind. Submission to God will renew it. I don’t know about you, but the good, pleasing, and perfect will plan sounds a lot better to me.