Everyone you've ever known, currently know, or ever will know, whether it's a co-worker or a fellow student, a shopper you nudged at the supermarket, or a total stranger who rode on the bus with you last month, is stupid. My family is stupid. My friends are stupid. Everyone I've ever known, currently know, or will ever know, is stupid. The answer is in three short words.
People are stupid.
This is my credo, my mantra, my First Law of the Universe. People are stupid. Think of everything you know, in every field imaginable, without the use of references. The best restaurants in New York City. Getting coffee stains out of a shirt.