IMHO, a term stupid is very subjective (damn, and what's not subjective in this world?). Some people may be good at sciences like math and physics, but have no knowledge of literature or history or lack common sense. Others can write a fine essay, but are poor when it comes to mathematics. And then some people may know something about most things, but don't know things that are known to more specialized people. I personally am terrible at writing stuff and speaking, but I am decent at sciences and can use logic effectively. It is impossible to learn about everything, so most people just learn about things that are more interesting to them. People usually judge others by their own standards, but they are variable from one person to another. But in my opinion, it is that most people just have some stronger sides and some weaker sides.