Thematic Bible: Who became vain

This, then, I say, and I testify in the Lord; ye are no more to walk, as also the other nations walk, in the vanity of their mind, being darkened in the understanding, being alienated from the life of God, because of the ignorance that is in them, because of the hardness of their heart, who, having ceased to feel, themselves did give up to the lasciviousness, for the working of all uncleanness in greediness;

for revealed is the wrath of God from heaven upon all impiety and unrighteousness of men, holding down the truth in unrighteousness. Because that which is known of God is manifest among them, for God did manifest it to them, for the invisible things of Him from the creation of the world, by the things made being understood, are plainly seen, both His eternal power and Godhead -- to their being inexcusable; read more.
because, having known God they did not glorify Him as God, nor gave thanks, but were made vain in their reasonings, and their unintelligent heart was darkened, professing to be wise, they were made fools, and changed the glory of the incorruptible God into the likeness of an image of corruptible man, and of fowls, and of quadrupeds, and of reptiles.