Plato used an allegory (story with hidden meaning, based on a comparison) to explain how what we perceive and know as human beings are mere "shadows" of what is really out there. He talked about a story of prisoners chained to a cave, who could only see shadows of what happened in the real world. These shadows were reflected on the walls of the cave. To the prisoners, the shadows were the only reality they knew. They thought the shadows were the real world. When one prisoner escaped and saw the real world, he wanted to tell the other prisoners about his experience. But they did not believe him. The world's shadows is all they knew... and all they wanted to know.

The film "The Matrix" also plays with this idea to some extent. In the Matrix, the world we experience is not quite the world as it is. Our reality is, in this sense, some kind of illusion. What kind of things do you think we cannot know, simply because we are human? If you could get the chance to take a pill that showed you the real, bare truth, would you take it? Or do you prefer to (comfortably) stay in our human world of shadows? How do you experience such shadows in your daily life?

Blue Pill or the Red Pill: The Matrix https://youtu.be/zE7PKRjrid4

Plato's Allegory of the Cave https://youtu.be/1RWOpQXTltA