Romans 1:21 NASB
“For even though they knew God, they did not honor Him as God or give thanks, but they become futile in their speculations, and their foolish heart was darkened.”
Those who did not follow the Mosaic Laws still had an internal knowledge of a Creator. God reveals Himself to all mankind and the disobedience of man manifests in a lack of honoring God’s moral code that has been placed in us and even by the revelation of the Mosaic Law and by Jesus Himself. They neither honor Him nor give thanks. Man was created to worship and to be in covenant with God. Whether we want to admit it or not, God designed us to worship Him, and if we don’t honor and give thanks to Him in worship and servitude we end up filling a void in our life by worshipping other things. This is the futility Paul speaks about. They were unable to produce any useful results in their pursuits and opinions. They (the Gentiles) created idols and worshiped physical gods which replaced the One true God even though they knew the truth. Out of their suppression of the truth and their disobedience their hearts became darkened. They were foolish, thinking that they were wise in their own eyes and sought their own desires and wasted their lives in futility and wickedness. Man cannot escape worship. Man in past ages worshipped Baal, in the Roman Empire they worshipped the emperor and today we worship ourselves.
This darkened heart produces evil upon evil. As man suppresses the truth of God and righteous living the depravity of his heart sinks lower and lower. Take Sodom and Gomorra, their suppression of the basic human decency towards one another was so severe that all the men in the city wanted to rape the angels that were visiting Lot and his family. Their wickedness was so vile that there was absolutely zero respect for right living. Can you imagine visiting family in a foreign town and all the neighbors attack you and demand the right to rape you and your family. You’d think they were possessed by demons! Absolute depravity comes from darkened hearts that blot out God from their conciseness and soul.