"We all need to have open minds..."
Hear that a lot, don't you? They teach us the maxim when we are young and in school, and we never seem to forget it, taking it with us into adult life and forever reminding others to do the same.
According to the Dictionary of Idioms by Christine Ammer, an open mind is one that is "receptive to different opinions and ideas". I like to define it as being willing to grant something the possibility of being valid and good, instead of disregarding it out of hand.
So, what's the big deal? It sounds good - and it is. We shouldn't mind hearing other's opinions and ideas. I know I wouldn't like to live in a world where the only voice I heard was mine.
The issue arises when someone attempts to subtly apply the principle to the realm of known fact. Should someone be receptive to something they know to be wrong?
Short answer - no.
If someone were to tell you that 2+2=5, you shouldn't be open-minded to it. You know it to be false - granting it the possibility of being right is a waste of time, and not mentally healthy. If you accept everything you hear and believe with equal validity, then you have bought into a much more dangerous lie - that there is no difference between what is true, and what is false.
In those instances, being close-minded is the best option. You don't have to be mean about it, of course, but unless there's a really good reason to take a second look, there's nothing wrong with tossing the errant postulation into your mental waste basket.
How does this affect normal life? Enter the misconception of the opinion.
"I try to keep an open mind, but not so open that my brains fall out."
- Harold T. Stone