Thematic Bible: Who became vain

So, I tell you this, and insist [on it] by [the authority of] the Lord: Do not continue to live with worthless thoughts as [unconverted] Gentiles do. Their understanding [of spiritual things] is darkened and excluded from the [spiritual] life that God gives, because of the ignorance in their minds and the stubbornness in their hearts. They have stopped caring [i.e., about morality], so God has abandoned them to lives of unrestrained indecency and to engage in all kinds of [moral] impurity, with a constant desire for more.

For God's extreme anger is being revealed from heaven against all the godlessness and wickedness of people who restrain the truth [from being known and obeyed] by their wickedness. For what is known about God is plain to these people [i.e., to the Gentiles], because God has made it clear to them. For since the creation of the world, God's invisible qualities of eternal power and divine nature have been clearly seen, [capable of] being perceived through the things that He has made. So, these people have no excuse [i.e., for not believing in Him]. read more.
Now they knew who God was, but they did not honor Him as God or thank Him [for their blessings]. Instead they engaged in their useless speculations and their foolish minds were filled with [spiritual] darkness. They claimed to be wise, but became fools, and exchanged the honor belonging to the immortal God for the statues of mortal men, and birds, and animals and reptiles.