Thematic Bible: Who became vain

This I say therefore, and testify in the Lord, that you should not walk from now on as other nations walk, 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. For they, being past feeling, have given themselves up to lust, to work all uncleanness with greediness.

For the wrath of God is revealed from Heaven against all ungodliness and unrighteousness of men, who suppress the truth in unrighteousness, because the thing which may be known of God is clearly revealed within them, for God revealed it to them. For the unseen things of Him from the creation of the world are clearly seen, being realized by the things that are made, even His eternal power and Godhead, for them to be without excuse. read more.
Because, knowing God, they did not glorify Him as God, neither were thankful. But they became vain in their imaginations, and their foolish heart was darkened. Professing to be wise, they became fools and changed the glory of the incorruptible God into an image made like corruptible man, and birds, and four-footed animals, and creeping things.