It's not always obvious right away. It's possible to know someone for weeks and months without knowing that that have the dumb. But then one day you're hanging out and you say something like "I wonder what the weather is going to be like tomorrow" and instead of checking the forecast they hit you with "I don't know but I hope the weatherman doesn't decide to make it rain tomorrow." So here are some signs someone might have an open position in their critical thinking department. And here are some of the dumbest things people have ever heard.