'Foolish' in the Bible

Because, having the knowledge of God, they did not give glory to God as God, and did not give praise, but their minds were full of foolish things, and their hearts, being without sense, were made dark.

Seeming to be wise, they were in fact foolish,

A teacher of the foolish, having in the law the form of knowledge and of what is true;

But I say, Had Israel no knowledge? First Moses says, You will be moved to envy by that which is not a nation, and by a foolish people I will make you angry.