Plato’s "Allegory of the Cave" is a concept devised by the philosopher to ruminate on the nature of belief versus knowledge. The allegory states that there exists prisoners chained together in a cave. Behind the prisoners is a fire, and between the fire and the prisoners are people carrying puppets or other objects. This casts a shadow on the other side of the wall. The prisoners watch these shadows, believing them to be real.

Plato posits that one prisoner could become free. He finally sees the fire and realizes the shadows are fake. This prisoner could escape from the cave and discover there is a whole new world outside that they were previously unaware of.

This prisoner would believe the outside world is so much more real than that in the cave. He would try to return to free the other prisoners. Upon his return, he is blinded because his eyes are not accustomed to actual sunlight. The chained prisoners would see this blindness and believe they will be harmed if they try to leave the cave.

(https://www.youtube.com/watch?v=SWlUKJIMge4)

Theseus owned a ship and the ship was entirely made of wood. Every time a piece of the ship needed replacing it was replaced with a metal part. This went on for a few years until eventually it was entirely made of metal.

On board the ship was a sailor who really wanted his own ship but could not afford one. So, he came up with a plan: every time Theseus decided to replace one of the wooden parts of his ship with a metal part the sailor would take the discarded piece of wood and hide it in his shed. When eventually he had collected all the wooden parts he re-assembled them into a ship again.

( https://www.philosophy-foundation.org/enquiries/view/the-ship-of-theseus )

( https://www.youtube.com/watch?v=SGAnLY46zAk )

( https://www.youtube.com/watch?v=iVlIZJTwgyQ )