Cognitive dissonance is one of the most useful concepts to have emerged from the practice of psychology. It describes that uncomfortable feeling we get when reality doesn't match what we believe. And isn't that most of the time?
It can lead to extreme neurotic states. I imagine North Korea's Kim Jong-un living in his fantasy state - in both senses of the word "state" - has a particularly serious case.
I've become used to it, having to deal with it most days when I pick up a newspaper and see that nothing in the world seems to be as it should be. Why are there people in extreme poverty when others have private planes? Why are children dying from diseases for which vaccines exist? And how did Lady Gaga end up at the Academy Awards, radiant in a shimmering ball gown, singing a medley from The Sound of Music?
That movie is 50 years old this year and seems to be as influential as ever. It gave me an early case of cognitive dissonance because I was taught by nuns at primary school. To an 8-year-old, nuns were nuns and nothing but.
They came into the classroom and taught us and then retreated into the adjacent convent where they lived and did ... nun stuff, I supposed. The mystery was part of the appeal.
So when a nun told me she and her sisters were off to see The Sound of Music, cognitive dissonance went off the chart. Nuns didn't go to the pictures.
To people without first-hand experience of nuns and their ways, they were just weird, the subject of rumours and innuendo, and what was all this "married to Jesus" malarkey about? Anyone who struggled with the concept of metaphor wasn't going to get nuns.
But you don't need 20-20 hindsight to see that in the 1960s, as today, there was a lot to be said for living a life focused on caring for others and one that did not require you to sacrifice your identity to a man.
This group of women had a mission and supported each other to achieve it. The concept of sisterhood with its feminist connotations sat comfortably with the concept of being a nun.
There was a strain of feminism that saw the vocation of nun as the ideal way to achieve its aims. It's still going strong and getting into trouble.
The Pope, who has liberals - Catholic and otherwise - positively swooning with admiration for his brand of pontifical cool, has cracked down on the main organisation of United States nuns, the Leadership Conference of Women Religious. Why? Because they supported Obama's healthcare reforms, which include birth control as part of health insurance. So nuns still have a fight on their hands.
And I hope they are still teaching the important values that anyone - believer or infidel - can live by.
They had absorbed and inculcated the Christian concept that all souls were created equal. They were very big on not judging people by how much money they had.
For their time, they were advanced on matters of religious tolerance. They worked hard and taught that hard work got results. And they laughed a lot. Nuns are among the giggliest people you will ever encounter.
They hardly ever spoke enthusiastically about the joys of self-flagellation or described in detail the tortures of the damned in hell. In fact, I can't remember that happening even once.
And there's another whopping dollop of cognitive dissonance. Like The Sound of Music, many of the ideas the nuns taught are still with us. Unlike the movie, however, they are still struggling to gain acceptance.