Plato’s allegory of the cave (from Republic) is probably the best known simile for truth-seeking. It’s based on a talk between Socrates and Plato’s older brother Glaucon. However, as much as it describes epistemology, it is metaphorically concerned with political corruption and ideological bigotry as well.
Plato’s allegory begins as follows: Socrates is likening the “prisoners” dwelling in a cave to us humans.
“From the beginning people like this have never managed, whether on their own or with the help of others, to see anything besides the shadows that are continually projected on the wall opposite them by the glow of the fire.”
This critical description of humans is fundamental to the allegory. Socrates argues that people consider “real” what they see (artifacts on the wall) and hear (sounds reverberating off the wall), thereby remaining ignorant about the truth.
Now, Plato sets the stage for the philosopher, the wise man, to free the prisoners, one by one, from “their lack of insight”.
At first, the prisoner that is now unchained can’t see the fire (which used to be behind him as the source of the artifacts on the wall). Steadily, though, he gets used to the light of the flame. Then, the prisoner has to be taken out of the cave into daylight, sometimes against his will. As described by Plato, this will often be a very hurtful process; knowledge can indeed be uncomfortable and deterrent to those who don’t want to see it. And because it is this way, sometimes people will even turn around and go back into darkness. This must be what Immanuel Kant meant when he was referring to enlightenment as overcoming cowardice and laziness (“sapere aude”). In addition, there is no shortcut to acquiring knowledge about the world than profound and radical educational efforts, as pointed out by the Prussian thinker Wilhelm von Humboldt.
“No, however, if someone, using force, were to pull him (who had been freed from his chains) away from there and to drag him up the cave’s rough and steep ascent and not to let go of him until he had dragged him out into the light of the sun, would not the one who had been dragged like this feel, in the process, pain and rage?”
Being in the daylight, the former prisoner needs to get accustomed to the alien brightness. Once he is able to see though, he will see the things themselves. At first, these things might be the stars and the moon in the night sky since they are more pleasant to look at than the sun.
Eventually, the liberated (and emancipated) person will be able to stare into the sun itself, being able “to contemplate of what sort [she] is”. He will consider himself lucky to have found wisdom while condemning the other prisoners for remaining blind to the truth.
Now, the allegory is getting more political. Socrates is asking Glaucon:
“Do you think the one who had gotten out of the cave would still envy those within the cave and would want to compete with them who are esteemed and who have power?”
For the emancipated prisoner going back into the cave would become “filling his eyes with darkness” again. Furthermore, the rare sparkle of wisdom in his eyes would cause ridicule among the prisoners. And if he dared to drag them into the light as well, the moment his hands tried to get hold of them, they would kill him.
The quintessence in Plato’s simile is that truth may sometimes hurt the holders of outdated beliefs and views. More importantly, though, truth may not always prevail and may eventually be sacrificed (together with the protagonists that were trying to advance their ideas) on the altar of political power and ideological bigotry.