Rationality: A fairy tale.

Please excuse my gross Euro-centric oversimplification:

Once upon a time some humans noticed that they could do things with their heads. When they closed their eyes they could imagine places, shapes and even weird abstract things like numbers. What's more is that they could use these ideas to solve problems and make their lives better. They called this thinking. When they talked to each other about thinking they quickly discovered that some of them were better at it than others. They called the people who were better at it, rational. When they looked around them, they noticed that they couldn't see much evidence of thinking in any other creatures and there was certainly no evidence of rationality. So they said "the rest of the world is shite because they can not have rational thoughts like us!"

A long time passed. The humans continued to use rationality to improve their lives. They built cities, made laws, farmed crops, waged wars, cured diseases and did some really hard sums. Then one day (perhaps it was the 17th or 18th century) some of the humans started to work on an idea. They said "Hey! why don't we use rationality to arrange everything that goes on in our lives!" Some of the other humans thought this sounded like a great idea while the rest of the humans just shrugged their shoulders and said "aright then". So the humans started to work on building really rational cities, farming really rational crops, waging really rational wars, curing really rational diseases and doing some really rational hard sums.

A long time passed. Then one day (in the 20th century) some of the humans started to say "Hey! does anyone else notice we aren't being rational anymore?". Most of the other humans just shrugged their shoulders and and said "nope, hadn't noticed". But the rest of the humans started arguing, some said that they were still being rational while others agreed that they weren't being rational anymore. And so the humans who thought they weren't being rational anymore started to say some very strange things that nobody else could understand while the humans that thought they were still being rational sat down and started to think some really rational thoughts about being rational.....