Derbyshire is a smart fellow, as I'm sure he'd be the first to admit, but I am often unimpressed by his ability to think clearly, which involves - among other things - making distinctions. IQ tests measure a certain kind of intelligence. Surely, we have all met Mensa members whose IQ might not be in doubt, but whose practical intelligence failed to impress. A talent for doing well in school - which usually means a talent for passing tests - is not necessarily a sign of high overall intelligence. No amount of schooling will make you more intelligent than you already are, but a certain amount can help give the impression that you are more intelligent than you are. Which is why many people think that someone who speaks well must be smart. There are, however, plenty of glib airheads. Walter Cronkite was once the most trusted man in America for no discernible reason other than that he had a resonant baritone and an avuncular manner. I am not suggesting Uncle Walter was dumb, but I have never seen any evidence that he was particularly brilliant, either.