There once was an invisible man. Though no one could see this man, they could see his shadow. Over the years, people tried to learn about the man by observing his shadow. They recorded their findings, carefully documenting every detail they saw in the shadow.
But they ran into some problems.
For one thing, the shadow didn’t always look the same to everyone. It would acquire the color and texture of whatever it happened to be resting on. And it seemed to change shape depending on the time of day and the angle from which people observed it. Some saw the shadow as extraordinarily tall and skinny, while others saw it as short and squat.