The ancient alchemists based their theories on ancient knowledge that was mainly passed down orally. They often used symbols and signs to decrypt what some believed should remain hidden. It's fair enough to ask, why did it have to remain hidden? The simplest thing to think is that hidden things fascinate more and when we look for them they become a real desire for research for us. But not only that, finding something hidden is also a game. Like the ancient hide and seek or the Cops and Thieves. Two categories of people. The “guardians” are the guardians, who ensure justice, while the thieves, at least as we know them today,  they are those who instead want to take something away from someone. The word thief derives from the Latin latro, “latronis”, derived, in turn, from the Latin latus, lateris which means side or side.  Originally it indicated a person who walked alongside a person of a certain rank in order to protect him from possible attacks by ill-intentioned people. The ancient thief was a shoulder, someone who walked with you, but not only that, his role was to protect you. Today we could call him the Bodyguard. When in the game Cops and Thieves, someone manages to avoid being seen by the guards and reaches the command post, the word he shouts is: "Tana free everyone". Its profound meaning is to reach a lair, a hiding place, something profound and when he manages to reach it he manages to free everyone. This ancient game has its roots in Platonic philosophy. The allegory of the cave (The Den) explains how one becomes a philosopher, that is, how one acquires the knowledge necessary to govern the city well, freeing oneself from opinions and accessing knowledge of reality. He considers knowledge to be divided into two kinds: sensitive knowledge, which is acquired through the senses and is aimed at the world of becoming, and intelligible knowledge which instead concerns ideas, that is, the immutable and certain elements of the world. The first type of knowledge is doxa, opinion, uncertain and variable; the second instead is episteme, science, certain and stable.  

At the beginning of Book VII of the dialogue, Socrates proposes an allegory to Glaucon. Imagine people who have lived since childhood locked in a cave, chained so tightly that they cannot even turn their heads. The cave has an opening that opens onto the outside, but the people who live there have their gaze turned towards the back wall, and cannot see the exit. Behind the prisoners, high up and away from them, there is a fire lit that sheds light. Between the fire and the prisoners there is a wall, long and low, like those that line country roads. Behind the wall, other people hold objects in their hands (statuettes of animals and men and other objects of all kinds) and make them protrude above the wall. The light from the fire therefore projects the shadows of the objects on the wall in front of the prisoners. Those shadows are the only things the prisoners have ever seen, forced as they are to stand there still, unable to turn around. So Socrates says those people believe that shadows are real objects. 

At this point, Glaucon interrupts Socrates and comments:«strange image describes strange prisoners» (515a). In fact, it is an unusual image, we know of no cases of people who have lived chained since birth, forced at the bottom of a cave. Surprisingly, Socrates replies that the prisoners are"similar to us". We too have only known shadows, projections of real objects, because truly real objects, ideas, are not known as such by everyone. It takes a good philosophical education to get out of the cave of opinion and access knowledge and science.