“They are both stupid and foolish, instructed by worthless idols made of wood!” (Jeremiah 10:8)
What are those who worship the idols the people of Israel were worshipping like? They are both stupid or brutish and foolish.
Matthew Henry reminds us why that is. “Those who make them are like them, senseless and stupid, and there is no spirit in them: no use of reason, or else they would never believe in such gods, and no sense of honour, or else they would never stoop down to their level.”
They are stupid. “Although in the works of creation they cannot help seeing the eternal power and godhead of the Creator, they still have become vain in their imaginations, not liking to retain God in their knowledge.”
They think they are “wise to have many gods,” but “it really was the most foolish thing they could be guilty of.”