Having presented us with the Analogy of the Sun and the Analogy of the Line, Socrates now in the conversation introduces the Allegory of the Cave. Socrates is here still trying to clarify the four levels of intellect, the two levels of belief, and the two levels of knowledge.
For this allegory, we are to imagine an underground Cave, whose entrance/exit leads upward to daylight. There are prisoners in the Cave who have been chained there since their childhood; they are chained to the ground and chained by their heads. They can see only the wall of the Cave in front of them. A fire is burning behind the prisoners; between the fire and the arrested prisoners, there is a walkway where people walk and talk and carry objects. The prisoners perceive only shadows of the people and things passing on the walkway; the prisoners hear echoes of the talk coming from the shadows. The prisoners perceive the shadows and echoes as reality.
If we unchain one of the prisoners and make him turn around, he would be frightened, pained by new physical movement, dazzled by the fire, unable at first to see. When he is told that the people and things he now perceives are more real than the shadows, he will not believe it. He will want to return to his old perceptions of the shadows as reality. When we drag him out of the Cave and into the World of Day, the sun will blind him. But he will gradually see the stars and the moon; he will then be able to see shadows in the daylight thrown by the sun; then he will see objects in the full light of day. The sun makes this new perception possible. If we took the prisoner back into the Cave, into his old world, he would not be able to function well in his old world of shadows.
For the allegory, the Cave corresponds to the realm of belief; the World of Day corresponds to the realm of knowledge. The sun stands for the Form of Goodness itself. If the prisoner were to be returned to the Cave, his old fellows would not believe his experiences, since they have always been imprisoned in their world, the Cave.
Thus, allegorically, we must release the prisoners from their Cave: We must give the Guardians the experience of education so that they can become the philosopher-kings of the Ideal State, because they will be able to know the Forms and, finally, Goodness itself.
But it is not enough that the prisoner, freed, now possesses knowledge. He must be returned to the Cave to enlighten his erstwhile fellows about the knowledge he now perceives.
Glaucon objects: He argues that for the enlightened prisoner to return to the Cave would make him unhappy. It would be a lot of work to lead his fellows into the light of a kind of new dawn of knowledge. Socrates here reminds us, again, that the business of rulers is not to make themselves happy; their happiness is to be realized in the happiness of every citizen in the Ideal State.
It is useful and probably necessary at this juncture that we compare the diagrams of the Divided Line (in the preceding analysis) and the Allegory of the Cave, following.
As the prisoner ascends from the Cave and emerges into the World of Day, allegorically his levels of intellect improve as his ascension progresses. Intellectually, the developing thinker moves from the level of imagining, upward to common-sense belief, thence to thinking, thence to the summit of Dialectic, also termed intelligence or knowledge. (Refer to the conversation about the levels of intellect in the preceding analysis.)
Plato seems to believe that all levels of intellect are somehow connected, not disparate; the person who achieves Dialectic has already subsumed the other levels in his progress. For example, the prisoner whom we help ascend from the Cave originally imagines that the shadows on the wall are "real things"; when he is permitted to perceive walkway, fire, people, and objects carried, he perceives the shadows as shadows of real things. He has learned something "new," but it is a learning predicated upon a previous assumption.
Interestingly, the American philosopher William James (1842-1910) believed that, in the world of ideas, ideas are connected by a kind of next-to-next relationship. James believed that the highest form of intellect is manifested in the ability to perceive similarities in apparently dissimilar things. James called this the ability to "subsume novel data." It is said that, in applying these ideas to the world of "things" and empirical phenomena, James anticipated the science of modern physics. James' theories are interestingly similar to Plato's.
The conversation of the Allegory of the Cave is highly allusive. At that point when we lead our prisoner from the darkness into the light, the prisoner will likely be physically dazed and intellectually perplexed. This condition (perplexity, confusion) is similar to that of Cephalus, who exits our conversation early, and Polemarchus at the very beginning of the present dialogue. Too, Socrates says that, in order to avoid perplexity, students should be schooled first in mathematics, then in moral philosophy, before they may understand the Good. Socrates suggests, further, that when the prisoner returns to the Cave in order to lead his fellows to the light of understanding, they may be so dismayed at their having been wrenched from their comfortable state of ignorance that they may want to kill him — a likely allusion to the death of Socrates, the historical man. And the allusion is amplified: If the first prisoner, now enlightened by his contemplation of Justice itself, were to be hauled into a courtroom and faced with the unenlightened quibbles of lawyers trained in sophistry, he probably would not be able to defend himself. A character named Callicles, in a different dialogue, derides Socrates with Socrates' inability to defend himself in a court of law (Gorgias 486 A).
We now continue the conversation in order to discover how the Guardians are to be given a higher education.
"Better to be the poor servant . . . ." Odyssey IX, 489.