Error is both seeing things that are not there, and just as importantly not seeing things that ARE there. The classic mistake is being factually wrong: for example, by believing that Jefferson was our second President. This is the sort of error know-it-alls never make.
The error they DO often make is ASSUME things to be true that aren’t, usually because someone they consider of equal intelligence and intellectual grandeur has said it first. Global Warming is a good example.
The great virtue of common sense is that it consists in seeing nothing other than what is there. It is unimaginative, and not focused on radical world-altering schemes. All the same, for practical purposes it performs quite well, and it absence is always a tragedy and a mistake waiting to happen.