trolls' ladder

You had to hand it to human beings. They had one of the strangest powers in the universe. Even her grandfather had remarked upon it. No other species anywhere in the world had invented boredom. Perhaps it was boredom, not intelligence, that had propelled them up the evolutionary ladder. Trolls and dwarfs had it, too, that strange ability to look at the universe and think ‘Oh, the same as yesterday, how dull. I wonder what happens if I bang this rock on that head?’

And along with this had come an associated power, to make things normal. The world changed mightily, and within a few days humans considered it was normal. They had the most amazing ability to shut out and forget what didn’t fit. They told themselves little stories to explain away the inexplicable, to make things normal.

—  Thief of Time - Terry Pratchett