4.1 What does it mean to have knowledge? The Allegory of the Cave.


By the end of this section you will discover:

  • The way in which philosophers understand knowledge as “true and justified belief.”
  • The difference between a priori knowledge and a posteriori knowledge.
  • How Plato’s Allegory of the Cave can be read as the discovery of higher, true knowledge.
  • The strengths and weaknesses of the Allegory of the Cave for understanding epistemology.

We use the verb “to know” in different ways. We can know another person, as in “Yes, I know Jeff” (acquaintance knowledge). We can know in the sense of “understanding” or relating, as in “I know you must be tired, so I will let you rest” (empathetic knowledge) We can use the word as an indicator of a procedure or ability, as in “I know how to speak German” (procedural knowledge). We can also use it in the general sense that we believe something even without proof, as in “I know that everything will turn out well.”

But when philosophers speak of knowing, they generally mean the attainment of a specific kind of knowledge: the knowledge that a statement is true. This is known as propositional knowledge.

The Meaning of Knowledge: Crash Course Philosophy #7

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For example, consider the statement:

“I know the earth is flat.”

This is a proposition that is either true or false. Philosophy holds that to know something is to have a true and justified belief about the claim. You will recall that when studying categorical syllogisms, we looked for something similar: a syllogism was said to be sound if it was both true and valid.

So, a philosopher would ask the question:

“How do you justify your belief that the earth is flat?”

In other words, “What arguments and proofs do you offer to convince us of this belief claim?”

How can we get to a true proposition? Different schools of epistemology will answer this question differently. Some, like the Skeptics, say the discovery of truth is not possible and is a wrong quest for philosophers. Others, like the Rationalists, speak of discovering clear and distinct ideas from mathematics and logic and using these to justify claims. The Empiricists, on the other hand, say that it is not reason but our sense experience that will best justify our claims to truth.

Propositional knowledge can be of two types, depending on its source:

  • a priori (or conceptual), where knowledge is possible separately from or “prior to” any experience and can be grasped with reason alone. An example of an a priori proposition is “all bachelors are unmarried men.” One does not need to go out and observe all bachelors in order to be able to know this. One can know this “before” observing, a priori.
  • a posteriori (or perceptual), where knowledge is possible only “after” or “posterior, to” experiencing the world. An example of an a posteriori proposition is “The tree outside my window is flowering.” Such a proposition requires one to observe the tree to know whether or not the statement is true.

One way to recognize these fundamental forms of knowing is to observe what happens in your mind in response to specific experiences. If, for example, I ask you to close your eyes and think of your smartphone, you will likely immediately conjure up a small picture of your phone. Perhaps you will also recall its texture or the sound of its ring. These mental recollections are examples of a posteriori or perceptual knowledge, the knowledge you have because you have already experienced your cell phone.

On the other hand, if I ask you to close your eyes and think of “representative democracy” you might find it difficult to conjure up perceptions. You may still know what this is, but you do not have a percept of it. Instead, you know it a priori or conceptually. Even if you managed to conjure up a mini picture of a senator addressing the senate, you have still not sufficiently expressed representative democracy. At best you have conjured up a percept (the senator) that points to or symbolizes the concept (democracy). Representative democracy is an example of an a priori idea that can only be known definitionally, not perceptually.

Keep in mind….

Try to observe how the mind responds to the following prompts to see if they are percepts or concepts. Then explain the difference between percepts and concepts to a friend and see how they do.

  • A stomach ache
  • Gastroenterology
  • The color of my dashboard
  • The smell of a candle
  • The agricultural industry
  • The chirp of a bird outside your window
  • Aviation


One of the most famous myths about the philosopher’s quest for knowledge comes from Plato in his “Allegory of the Cave” in Book 7 of Republic.

Excerpts from Plato’s Republic–The “Allegory of the Cave”

In this excerpt, consider:

What is the initial setting of the allegory; can you visualize it?

Notice the way Plato uses the verb “to see” throughout the allegory. Does he use it in more than one way?

What does this opening scene symbolize?

Socrates: And now, I said, let me show in a figure how far our nature is enlightened or unenlightened: –-Behold! human beings living in an underground den, which has a mouth open towards the light and reaching all along the den; here they have been from their childhood, and have their legs and necks chained so that they cannot move, and can only see before them, being prevented by the chains from turning round their heads. Above and behind them a fire is blazing at a distance, and between the fire and the prisoners there is a raised way; and you will see, if you look, a low wall built along the way, like the screen which marionette players have in front of them, over which they show the puppets.

Glaucon: I see.

Who are these puppeteers? Why are they doing this?

Socrates: And do you see, I said, men passing along the wall carrying all sorts of vessels, and statues and figures of animals made of wood and stone and various materials, which appear over the wall? Some of them are talking, others silent.

Glaucon: You have shown me a strange image, and they are strange prisoners.

How does what follows illustrate the Rationalist distrust of the senses?

Socrates: Like ourselves and they see only their own shadows, or the shadows of one another, which the fire throws on the opposite wall of the cave?

Glaucon: True how could they see anything but the shadows if they were never allowed to move their heads?

Socrates: And of the objects which are being carried in like manner they would only see the shadows?

Glaucon: Yes.

Socrates: And if they were able to converse with one another, would they not suppose that they were naming what was actually before them?

Glaucon: Very true.

Socrates: And suppose further that the prison had an echo which came from the other side, would they not be sure to fancy when one of the passersby spoke that the voice which they heard came from the passing shadow?

Glaucon: No question.

Socrates: To them, the truth would be literally nothing but the shadows of the images.

Glaucon: That is certain.

Again, here, note Plato’s concern with sight/blindness.

Socrates: And now look again, and see what will naturally follow if the prisoners are released and disabused of their error. At first, when any of them is liberated and compelled suddenly to stand up and turn his neck round and walk and look towards the light, he will suffer sharp pains; the glare will distress him, and he will be unable to see the realities of which in his former state he had seen the shadows; and then conceive someone saying to him, that what he saw before was an illusion, but that now, when he is approaching nearer to being and his eye is turned towards more real existence, he has a clearer vision, what will be his reply?

And you may further imagine that his instructor is pointing to the objects as they pass and requiring him to name them, will he not be perplexed? Will he not fancy that the shadows which he formerly saw are truer than the objects which are now shown to him?

Glaucon: Far truer.

Socrates: And if he is compelled to look straight at the light, will he not have a pain in his eyes which will make him turn away to take and take in the objects of vision which he can see, and which he will conceive to be in reality clearer than the things which are now being shown to him?

Glaucon: True.

Socrates: And suppose, once more, that he is reluctantly dragged up a steep and rugged ascent, and held fast until he’s forced into the presence of the sun himself, is he not likely to be pained and irritated? When he approaches the light his eyes will be dazzled, and he will not be able to see anything at all of what are now called realities.

Glaucon: Not all in a moment.

What is this world outside the cave? What do you think Plato is trying to say here?

Socrates: He will require to grow accustomed to the sight of the upper world. And first he will see the shadows best, next the reflections of men and other objects in the water, and then the objects themselves; then he will gaze upon the light of the moon and the stars and the spangled heaven; and he will see the sky and the stars by night better than the sun or the light of the sun by day?

Glaucon: Certainly.

Socrates: Last of all he will be able to see the sun, and not mere reflections of him in the water, but he will see him in his own proper place, and not in another; and he will contemplate him as he is.

Glaucon: Certainly.

Socrates: He will then proceed to argue that this is he who gives the season and the years, and is the guardian of all that is in the visible world, and in a certain way the cause of all things which he and his fellows have been accustomed to behold?

Glaucon: Clearly he would first see the sun and then reason about him.

Having seen the world outside the cave, the prisoner now returns to his former comrades.

Socrates: And when he remembered his old habitation, and the wisdom of the den and his fellow prisoners, do you not suppose that he would felicitate himself on the change, and pity them?

Glaucon: Certainly, he would.

Socrates: And if they were in the habit of conferring honors among themselves on those who were quickest to observe the passing shadows and to remark which of them went before, and which followed after, and which were together; and who were therefore best able to draw conclusions as to the future, do you think that he would care for such honors and glories, or envy the possessors of them? Would he not say with Homer, “To be the poor servant of a poor master,” and to endure anything, rather than think as they do and live after their manner?

Glaucon: Yes, I think that he would rather suffer anything than entertain these false notions and live in this miserable manner.

Socrates: Imagine once more, such an one coming suddenly out of the sun to be replaced in his old situation; would he not be certain to have his eyes full of darkness?

Glaucon: To be sure.

How would the returned prisoner now view life at the bottom of the cave?

Socrates: And if there were a contest, and he had to compete in measuring the shadows with the prisoners who had never moved out of the den, while his sight was still weak, and before his eyes had become steady (and the time which would be needed to acquire this new habit of sight might be very considerable) would he not be ridiculous? Men would say of him that up he went and down he came without his eyes; and that it was better not even to think of ascending; and if anyone tried to loosen another and lead him up to the light, let them only catch the offender, and they would put him to death.

Glaucon: No question

(Plato, “Republic, Book 7,” in PLATO IN TWELVE VOLUMES, trans. Paul Shorey, vol. 5 and 6, 12 vols. (Cambridge, MA: Harvard University Press, 1969), http://data.perseus.org/citations/urn:cts:greekLit:tlg0059.tlg030.perseus-eng1:1.)

Here Plato has Socrates metaphorically describe the struggles of the philosopher who “sees” without the senses while at the same time indicating both the difficulties in attaining such sight as well as the great rewards of full rational vision.

Strengths and weaknesses of the “allegory of the cave” as a guide to epistemology.

Here are some of the notable strengths and weaknesses of the allegory of the cave from Plato’s Republic as a metaphor for understanding epistemology:

On the one hand:

  1. The story dramatically conveys the compelling distinction between inferior awareness based on appearances vs an awakened grasp of deeper reality.
  2. It explains why surface truth may actually distort our knowledge and how reasoning can break from common opinions to uncover truer underlying forms.
  3. The educational ascent illustrates the development of understanding, the initial pains facing truths, and the difficulty returning to the darkness to try to share what you have learned.

On the other hand:

  1. The stark light/dark dualism risks wrongly implying that one is either in total ignorance or full enlightenment rather than more the likelihood that all knowlege exists on a spectrum.
  2. The story underplays other ways to gain knowledge–by experience, data, logic checks – and focuses predominately on a kind of transcendental insight.
  3. Its imagery does not make a strong distinction between theoretical knowledge and the full virtuous wisdom that should guide our action.
  4. It doesn’t address the potential fallibility of reasoning or arguments that may modulate confidence in our conclusions, instead it suggests reason can bring indisputable certainty.

So while succeeding marvelously as a vivid thought-provoking illustration differentiating shallow appearance from penetrating reality, overtones of absolutism and rationalist escapism from the world remain philosophically objectionable.



Works Cited

CrashCourse, director. The Meaning of Knowledge: Crash Course Philosophy #7. YouTube, YouTube, 21 Mar. 2016, https://youtu.be/kXhJ3hHK9hQ. Accessed 5 Apr. 2022.


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PPSC PHI 1011: The Philosopher's Quest by Daniel G. Shaw, Ph.D. is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License, except where otherwise noted.

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