Given the flying car, I'd say Arthur Weasley isn't too concerned with observing the letter of the law. In view of that, and the fact that he is (presumably) literate in the English language and "Muggle Artifacts" aren't "misused" until they're enchanted, I'd say that either his apparently boundless ignorance is a spot where Rowling derped, or he's actively baiting Muggleborns into teaching him by pretending to be stupider than he is. In the latter case, Arthur probably has a hidden bookcase somewhere filled with engineering books.
I like how Rowling lets her protagonists make mistakes. I strongly dislike how, in Ron Weasley's case at least, they make one mistake over and over again. Seriously, the boy simply never grows up!
I like how Rowling lets her protagonists make mistakes. I strongly dislike how, in Ron Weasley's case at least, they make one mistake over and over again. Seriously, the boy simply never grows up!