An incident that happened in my father's driveway this morning has made me want to share a little something with y'all. My little brother accidentally backed his mother's car into my car where his intension was to simply start it for her. He evidently didn't know what he was doing. He's not stupid for not knowing how to operate a motor vehicle, he's stupid for not knowing that he didn't know.
Stupidity. It ain't about not knowing anything other than what you don't know. A corollary to this is wisdom being knowing the limitations of your knowledge. Infinite stupidity is thus knowing nothing and believing that you know everything while infinite wisdom is knowing that you know nothing (except that you know nothing (except that you know nothing (except ...))).
Don't take my word for it. I have found that stupidity is best understood by experiencing it.