'Foolish' in the Bible

I have a duty to perform and a debt to pay both to Greeks and to barbarians [the cultured and the uncultured], both to the wise and to the foolish.

For even though they knew God [as the Creator], they did not honor Him as God or give thanks [for His wondrous creation]. On the contrary, they became worthless in their thinking [godless, with pointless reasonings, and silly speculations], and their foolish heart was darkened.

and [that you are] a corrector of the foolish, a teacher of the [spiritually] childish, having in the Law the embodiment of knowledge and of the truth—

But I say, did Israel fail to understand [that the gospel was to go also to the Gentiles]? First Moses says,“I will make you jealous of those who are not a nation (Gentiles);With a nation that lacks understanding I will make you angry.”