Theory of Forms


Theory of Forms

Lecture for Phi100: Introduction to Philosophy

Prepared by Ms. Perez for Hopkinsville Community College; 2013

Created 2013 Updated: Feb 24th, 2018


The Theory of Forms was Plato's answer to objective knowledge. He devised examples to illustrate the perfect 'Form' of objects as they exist in the realm of the 'Forms'. He used a metaphor called the Allegory of the Cave to show how our flawed senses, weak perception, and passive reason hindered our ability to see objective knowledge. Theory of Forms represents Plato's idea that everything we see around us is an imperfect reflection of a true form, the only level at which things really exist must be the level of single properties separated from particular objects. Plato constructs the world where subjective opinion exists in one realm, the material realm, and true knowledge exists in another abstract realm, the transcendent realm of the forms.


  • Forms: A Form is an abstract property that is pure, transcendent, timeless, and real.
  • The Good: Ultimate Form of Knowledge
  • Innatism: characteristic you are born with

Key Philosophers:

Plato & Socrates

Primary Source Material:

Student should read the following before continuing. 

THE ALLEGORY OF THE CAVE Republic, VII 514 a, 2 to 517 a, 7 

By Plato


Biographical sketch provided by Mr. Richard Kraut of The Stanford Encyclopedia of Philosophy, Plato.

"Plato (429-347 B.C.E.) is one of the most dazzling writers in the Western literary tradition and one of the most penetrating, wide-ranging, and influential authors in the history of philosophy. An Athenian citizen of high status, he displays in his works his absorption in the political events and intellectual movements of his time, but the questions he raises are so profound, and the strategies he uses for tackling them so richly suggestive and provocative, that educated readers of nearly every period have in some way been influenced by him, and in practically every age there have been philosophers who count themselves Platonists in some important respects. He was not the first thinker or writer to whom the word "philosopher" should be applied. But, he was so self-conscious about how philosophy should be conceived, and what its scope and ambitions properly are, that he transformed the intellectual currents with which he grappled, that the subject of philosophy, as it is often conceived-a rigorous and systematic examination of ethical, political, metaphysical, and epistemological issues, armed with a distinctive method-can be called his invention. Few other authors in the history of Western philosophy approximate him in depth and range: perhaps only Aristotle (who studied with him), Aquinas, and Kant would be generally agreed to be of the same rank."1

Our Reason is Hindered by All Of These

Plato's The Allegory of the Cave is a metaphor for our flawed senses, our weak perception, and our reason is hindered by all of these. Allegory of the Cave, appears in Plato's The Republican of Plato's more popular and famous works, as an extended metaphor for how we perceive reality. The Theory of Forms represents Plato's idea that everything we see around us is an imperfect reflection of a true form, the only level at which things really exist must be the level of single properties separated from particular objects. Plato constructs the world where subjective opinion exists in one realm, the material realm, and true knowledge exists in another abstract realm, the transcendent realm of the forms. In contrast, his pupil Aristotle famously denounced such a notion when he claimed that "the senses were the only true form of knowledge" and, further that all general ideas are formed in our realm of perception, not in things outside nature (Durant 527).

Plato believed that knowledge was easily accessible to everyone but the problem was recognizing pure knowledge. Let us ask the question another way, can you ever know knowledge in a pure state?

Plato claimed that the fundamentals of knowledge couldn't be gained solely through reason or experience. We must come to recognize and understand knowledge by way of the internal. Meaning, we recognize and recall knowledge that is in us already; innate and inherent knowledge present since before birth. The appearance of the world around us is external. We soak in information from our senses. Plato believed our senses were deeply flawed. The only way to understand true pure knowledge was to seek the Good, or objective pure knowledge.

For Plato, all things are a recollection because all knowledge is innate within us. Plato offers an example by way of his parable The Allegory of Cave.

The Form of the Good

The Allegory of the Cave is a parable from Book VII of Plato's, The Republic, a long involved look into the making of Utopia -- perfect justice and virtues. The parable speaks of a group of men chained up with their heads affixed towards a wall. They're unable to move their heads left or right. As they sit there, shadows dance on the wall in front of them. These shadows represent all they know to be real. This is their reality being they do not know they're prisoners, nor do they know the shadows are projections; this is their reality. One day, one of the prisoners is released from his chains. He turns to see his captors by the fire and people walking in front of the fire holding shapes. He looks back onto the cave wall and realizes the shadows are no more than the projection of those shapes. He stumbles towards the opening of the cave where bright light shines. When he exits the cave, he sees a new world of wonder and clarity. Outside the cave, Socrates tells us, is a Form of the 'Good', and 'the Good' is what all men should seek in life. The Good is the ultimate path to Knowledge. The Good allows the mind to understand all things by their essence, not its appearance, and not tainted by our hindered perception.Without the Good, we will forever be a prisoner bound to our chains of appearance and perception. The prisoner runs back into the cave to tell his fellow prisoners what he has discovered but, they only see him as a shadow on the wall. Socrates emphasized this is the Human Condition. We are satisfied with a passive perception of the world and do not seek a higher understanding but, those who do seek a greater understanding will gain the ultimate knowledge. The seekers of wisdom are what Socrates called the Philosopher King.

Enlightened and Un'enlighted

This wisdom is not hard to find. Socrates tells us the Forms exist in all of us. We do not have to seek the exit of the cave because within our mind the Forms already exist. You can experience the outside of the cave inside the cave as well. As soon as the prisoner realized the shapes were a projection, he was already releasing himself to the Forms. In our mind exists all knowledge. We need only look passed our passivity, our passions, and our vices. Knowledge is there for the taking, you need only be open to seeing it.

Where is it?? It's in you already, Plato would say yes. Let's begin to break down this story with the opening paragraph:

[Socrates] And now, I said, let me show in a figure how far our nature is enlightened or unenlightened:--Behold! Human beings living in a underground cave, which has a mouth open towards the light and reaching all along the cave; 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.

Socrates asked Glaucon to analyze the effects of 'those who are educated' vs. 'those who are not' on knowledge. In other words, If knowledge were to stand in the center of the room and the only way out was through one of two doors, what would be the appearance of knowledge on the other side. One door is the face of the educated, while the other is the face of the uneducated. He sees a bewildered look on Glaucon's face so he paints him a picture by saying, --Behold! Human beings living. He tells him of bound prisoners forced to stare at a wall with shadows on it. As you read, this is a strange sight and surely something odd for most of us. I want to draw your attention to a pattern I saw while I read it. Socrates seems to address a particular aspect of the prisoners... their senses.

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

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

[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 passers-by spoke that the voice which they heard came from the passing shadow?

[Glaucon] No question, he replied.

[Socrates] To them, I said, the truth would be literally nothing but the shadows of the images.

He asked if they can see anything (sight), do they know what are the shadow's voices (speak), and what can they hear (hearing). Then Socrates says, the truth would depend on the senses or sight, sound and hearing confirm the truth; as if the senses form and confirm what is real.

[Socrates] And now look again, and see what will naturally follow if the prisoners are released and disabused of their error.

Draw a Perfect Ball

Let's pause on that word, 'release'. What are the prisoners released from? It appears they're being released from the grips of their senses. What implications come from obtaining knowledge sans our senses?

Socrates then asked Glaucon a series of questions: What compels the prisoners to stand up? Who compels the prisoner to stand? What was life like bound vs. unbound? How is vision corrected now that he is released?

Socrates speaks the heart of his argument, what is more real, the concept of the shadow or the shadow itself? Let's consider a ball.

What is a ball? Why not take a minute to draw a ball, any ball you like- soccer, football, or a basketball? How about just draw anything circular? Let's say I drew a ball too, a soccer ball to be exact. Did my ball, or circular object, match yours? Most likely it did not but we both understood the concept of the 'circular ball'. The ball we drew was a concept and will remain in our minds as such. Together, we can recognize the notion of a perfect ball, even if we can't agree on what exactly a ball should look like. We know a ball must be circular in nature; perhaps it will bounce and must hold air in order to perform.

Although they are not completely perfect, we can agree that the ball exists in our mind in perfect 'form'. Plato claims the 'form' of the ball is the only ball that exists and all others, yours and mine, are imperfect copies, or reflections of the ball. The 'ball' that you drew exists in the material world but its likeness exists in another realm. Its roundness exists independently of the ball and will never change, and in the realm of the Forms, its roundness will still exist if the ball is deflated or destroyed. It is the material world, perceived through the senses, where things change. The realm of Forms is permanent and immutable.

Let's continue with the reading.

[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 is now called realities.

After the prisoner is dragged to the surface, Socrates begins with another pattern. The prisoner sees objects from lowest to highest.

[Socrates] He will 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?

Shadows on the wall

The prisoner sees shadows, then man, and then objects in the water. Consider for a moment what a shadow looks like. It's distorted, skewed, and blurred. The image of man is similar from afar. We aren't quite sure what we're looking at until we adjust our vision or move closer. It's important to point out that he mentioned 'objects in the water'. The prisoner is still using his senses to see everything and to him, nothing makes sense. The ripples in the water distort the objects underneath and the shadows still appear foreign.

[Socrates] Last of 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.

Once his eyes adjust he sees the study of things, the study of things above like the sky and stars, and finally the sun. Why is it we cannot look directly at the sun, I wonder? Socrates asked that question, "Why do we need to study the source?" Think for a moment the appearance of a flower. If you look at a field of flowers, do you not see the blooms first? We see the blooming flower but not the stem, nor do we see the seed below, which is the source. But, we know without the seed, or the source of the flower, we would not have the flower. We know the seed is there even though we aren't always looking at it; similar to the Sun. This begs the question, why do we see in reverse? Could it be our senses absorb too fast for our reason to process? Does our reason provide shortcuts that skew beliefs? Surely this cannot be pure knowledge we obtain?

[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?

Finally, our prisoner has learned to look past his senses and infer the information. INFER - here's a word I want us to define.

Infer: deduce (information) from evidence and reasoning, rather than from explicit statements, or statements that leave no room for doubt.

To infer means you've come to a logical conclusion by means of deduction from evidence and reasoning - basically, you aren't just guessing. The prisoner finally, after going through the cave opening, adjusting his vision to the new world, now infers what it all means. He says, "in a certain way the cause of all things", he concludes that without the sun, there would no shadows, no men, no objects in the water, nor would there be anything to see at all. The sun is the source of all things; it's the cause of all things. Socrates wants us to know that without the sun, which is the source of all things, we would not have anything at all. We come to understand the Sun is wisdom. We should all seek wisdom in our lives, Socrates says. This brings us back to the driving question: How does this innate quality affect our ability to reason and obtain knowledge?

Our prisoner recalls the source of all knowledge was the fire but now it's the sun. He returns back to the cave and sees the fire and bound prisoners with their eyes affixed to the wall.

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

What was the wisdom of the cave?

Clearly, he believed he was learning something. The world he knew before was real to him. Whatever beliefs he had about the world are still fresh and real in his mind. But now, he sees something else, something pure and everlasting, something older than time. Plato called these items of perfection, Forms. The prisoner ascended out of darkness, confused and unsure, and through his weak eyes sees reality through by means reason and contemplation, not the raw data from his senses.

The Forms are:

  • Pure
  • Transcendent
  • Archetypical
  • Real
  • First Cause
  • Interconnected

Returning to the BALL example. All balls share a likeness to the ideal ball, and it's this relationship to the ball that connects all balls.

The ideal, abstract, or concept of the ball is the Form of the ball. The actual ball, the ball that you can touch and feel is the material replication of the ball. (Note the capital F - we aren't talking about the word 'form', we're talking about a 'Form')

For example, if we want to look at the Form of the ball, we need to separate the ball from all its attributes. We would separate its roundness, its color, its material, and its function; each attribute would be a Form in its own right, existing outside our time and space in perfect conceptual 'Form'.

Let's look at 'roundness'. Every object that is round, or circular, pulls from the Form of roundness. Or, let us look at the attribute of color - all things that are red pull from the Form of red that exists in the intelligible realm of the Forms. In this sense, the Forms are real and all objects in our material world are mere copies of their Form. The Forms are pure and perfect, which, if you think about it, they could not exist in our realm being our world, is far from pure. Consider the Forms as perfect models, or the perfect idea of the object.

The Forms have a hierarchy as well. All Forms are systematically ordered with lower Forms leading to higher Forms. Ultimately, all Forms lead to the highest of the Forms - the Form of the Good. In the story, Socrates uses the Sun as an allegory for this Form. The prisoner learned that without the Sun there would be nothing. So, too, without the highest of Forms, there would be nothing; Goodis the source and origins of all things because it's the highest of the Forms.

All Forms fall under the Good and being all objects in our material world descend from their perfect Form, the Forms become the first cause of their object. In that way, all the Forms are interconnected. Returning to the story.

[Socrates] This entire allegory, I said, the prison-house is the world of sight, the light of the fire is the sun, and you will not misapprehend me if you interpret the journey upwards to be the ascent of the soul into the intellectual world according to my poor belief, which, at your desire, I have expressed whether rightly or wrongly God knows.

The Cave is our Senses

The prison-house is the cave, or more poignantly the cave is our senses. The light of the fire is our wisdom, or more like our source of reason. The release from our senses and ascent into the intellectual world of the Forms is a shock to our beliefs. Our beliefs are questioned and securitized for authenticity. Earlier inThe Republic, before Socrates mentions the Cave, he offers two other examples of knowledge, the Simile of the Sun and the Divided Line.

"Now take a line which has been cut into two unequal parts, and divide each of them again in the same proportion, and suppose the two main divisions to answer, one to the visible and the other to the intelligible, and then compare the subdivisions in respect of their clearness and want of clearness, and you will find that the first section in the sphere of the visible consists of images. And by images, I mean, in the first place, shadows, and in the second place, reflections in water and in solid, smooth and polished bodies and the like, Imagine, now, the other section, of which this is only the resemblance, to include the animals which we see, and everything that grows or is made" (The Republic: the Divided Line: 509d).

As you climb upwards on the dividing line, you enter into the area of the Forms.

"A line is cut into two unequal parts, and each of them is divided again in the same proportion. The two main divisions correspond to the intelligible world and to the visible world. One section in the visible division consists of images, that is, shadows and reflections, and is accessed through imagination. The other, higher section in the visible division consists of sensible particulars and is accessed through belief. One section in the intelligible division consists of Forms and is accessed through the mind, but via sensible particulars and hypotheses, as when geometers use a picture of a triangle to help reason about triangularity or make an appeal to axioms to prove theorems. The other, higher section in the intelligible division also consists of Forms but is accessed by understanding, a purely abstract science which requires neither sensible particulars nor hypotheses, but only an unhypothetical first principle, namely, the Form of the Good. The purpose of education is to move the philosopher through the various sections of the line until he reaches the Form of the Good" (The Republic: The Divided Line: 509d).

As gracious as this description is for us, it tends to be very technical, so let's break it down.

The Divided Line

The vertical line is the wanderer between two worlds (reason). It travels between the Visible Material World (where you live and breathe) and the Intelligible World (where you think and perceive). You cannot physically cross between these two realms but you can move back and forth over it through your mind. On the bottom, we have the Visible world, where we live and breathe, here we can touch the ball, bounce the ball, and see the ball. In the Visible world, we have the image of the ball available to the natural senses. Above the great Divided Line, we have a concept of the ball. We can think of its circular nature and its ideal existence. In this realm, we have what Immanuel Kant called the noumenal or the Intelligible World. In this realm, Plato says the Forms exist but cannot be seen, only thought.

Exercise: Move Up the Line

Let's pick a random topic and move it across the Divided Line and expose our ideas to it.

Let's pick flowers. Picture a flower in your mind.

What does the flower look like? What impressions of the flower do you have of it? Where did you first learn about flowers?

Plato tells us the flower, the one we see, is only an imitation of the pure flower existing in the realm of the Forms. That means when you see a flower it is only at stage one.

At the bottom of the line, the flower exists in our material world as an illusion based on imagination and myth. We believe it to be a flower because that is what we were told a flower to be but, is it really a flower? But does the flower we see represent all the flowers in the world? Compare the flowers below, are they what you expect in a flower?

The flower in my mind is much different than that weird flower with SPIKES! Why is it, when we picture a flower it's never an ugly flower? Why is it always a beautiful flower? Well, I'm assuming you think that way but, you get my point. If we move the flower across the Divided Line, Plato tells us, the flower changes from our perception of the flower to the pure Form of a flower. Each step along the way, the flower changes. Moving up the line to the Dianoia stage, or the stage where our assumptions are tested with systematic logic and reason, the flower is no longer represented as something only I perceive it to be but moves towards the universal idea of the flower. We, as the combined collective consciousness, can each instinctually think of this pure perfect flower-the ideal Form of the Flower. Do you see how the flower changes as it moves up the line?

Plato says, even if you have never been introduced to a flower, the idea of the perfect flower innately resides in your mind, waiting to be recalled. Ultimately, this means I will never understand the true nature of a flower until I have explored every flower. So, then, I have to wonder, what subconscious ideas were tainting my perception of the flower, more importantly, what subconscious ideas are affecting other ideas I have on objects, or people, or ideas?

For this exercise, I want you to pick an object, type of person, or idea and using the blue image above, move the idea, person, or thing, up the line. You could pick a car, house, or dog. You could pick a lover, parent, or child, you could even use war, religion, or education - whatever you like. How does (insert choice here) change from Eikasia to Noesis? Draw it out if it helps you. But, you must tell me how the object changed at each level, and ultimately, what does this exercise reveal about our understanding at each level?

How would the Dividing Line look if you added something more complex such as ideas and images of Christianity, Islam, or a political issue such as Gun Control or Abortion Rights?

How do we see 'religion' as opposed to how it would be represented in its pure state?

The Simile of the Sun

Let's try another experiment, let's redraw that ball, except this time, turn out all the lights and close your eyes. Now draw the ball. Did you do it? How did it look? Maybe we should turn the lights back on and open our eyes. Plato said that in order for us to see in the Visible World we need the sun. The sun illuminates the Visible World so we can see. Similarly, in the Intelligible World, you cannot understand knowledge without the illumination of the Good shining upon it. It is the 'form of the Good' that makes it possible for us to understand knowledge and know how to live. In all things, we do, we must reach passed our passive understanding and reach for the Good - the objective sense of knowledge. Might be a long reach, right?!

Three questions come to mind:

  • Can you go back to ignorance?
  • Can you un-know something?
  • Can you enlighten those who live in ignorance? Why?

[Socrates] But, whether true or false, my opinion is that in the world of knowledge the idea of Good appears last of all, and is seen only with an effort; and, when seen, is also inferred to be the universal author of all things beautiful and right, parent of light and of the lord of light in this visible world, and the immediate source of reason and truth in the intellectual; and that this is the power upon which he who would act rationally, either in public or private life must have his eye fixed.

Socrates leaves Glaucon with a few musings about the Forms. Why is it we don't seek the origins or authenticity of an idea before we believe it? Why are so many things taken at face value? He says, "and is seen only with an effort". We can assume ideas exist in a tainted state because the chains of perception bind us. But, if we can see past our own broken sense data, and properly infer the origins of an idea or belief, we are responsible for that new knowledge, "and, when seen, is also inferred to be the universal author of all things beautiful". By responsible I mean we are now placed in a position to look past the fire, out the cave, and affix our eyes on reason and wisdom; one "would act rationally" and pursue the Good.

Historical Context

It's easier to understand the Theory of Forms if we put Plato in historical context. Imagine a time when everything changes, at the whim of the gods. Let me give you a few relatable examples.

  • Religion: As a follower of a particular faith, you have allowed yourself to follow a set of principles, i.e. do not steal, lie, or cheat etc. What if the clouds opened and your god sent you a new set of principles to follow, i.e. now you have to steal, lie, or cheat? If you want to be a follower of that god, you have to comply.
  • Work: As an employee, you have to follow the rules or you're fired. Then one day you show up to work and all the rules have changed, you have new procedures, and you have a new boss.
  • Student: As a student, you go from instructor to instructor, each with new due dates, new syllabus guidelines, and new discussion board rubrics.

Wouldn't it be nice if there was one universal way of doing everything?! Wouldn't it be nice if there was one universal moral code that never changed and applied to everyone?

Maybe students would stop worrying about replying to three, two, or four other students. Maybe employees would enjoy going to work, and maybe peace would befall the Earth.

As a frustrated member of the Greek society, Plato heard Socrates speak of such universal ideas. However, instead of calling them principles, rules, or rubrics, Socrates called them Forms. Socrates thought long and hard about the Forms. He elaborated on each one in great detail in his treatise, The Republic.

Answer the questions below for this assessment: (not an assignment, just food for thought)

1) Describe how the people in the cave are situated in Plato's parable. Why can't they move their legs or necks to take a look around? What is the only thing they are capable of seeing? What is their only source of light? What do these prisoners trapped in the cavern belief is real?

2) What are the stages of the liberated prisoner's experience outside the cave? How do the prisoners react when they first see sunlight? Why? If a prisoner is released from the cave and compelled to look toward the light, what will he experience? Why? What are some things the allegory suggests about the process of enlightenment or education?

3) What does Plato's Allegory of the Cave tell us about how we recognize things? What does Plato's cave tell us about what we see with our eyes? What is the Truth according to Plato in this allegory?

4) Describe an experience you have had in which something that looked true turned out to be false, or was false turned out to be true. How is it possible that people can believe in illusion and accept it as reality? What sometimes happens to people when the illusion is shattered and reality is revealed?

5) Describe other "caves" in modern life in which people might be "imprisoned" or feel "imprisoned". If the liberated prisoner goes back to the cave and tries to explain to his former fellow prisoners, what kind of reaction will he get? Why?

6) To what extent do you find Socrates point about the human tendency to confuse "shadows" with "reality" relevant today? What could be the elements that prevent people from seeing the truth, or regarding "shadow" as the "truth"? (Be sure to use an example from Current Events).


  • 1Kraut, Richard, "Plato", The Stanford Encyclopedia of Philosophy (Fall 2013 Edition), Edward N. Zalta (ed.), <>.
  • 2Burton, Neel. "Plato's Metaphors: The Sun, Line, and Cave." Outre Monde. N.p., n.d. Web. 27 July 2014.
  • 3Plato. "The Internet Classics Archive ' Meno by Plato." Meno by Plato. The Internet Classics Archive, n.d. Web. 27 July 2014.
  • 4Durant, Will. "The Story of Philosophy." Washington Square Press. New York. 1961.
  • 5Gonzalez, Pedro, Dr. "The University Bookman." : Plato's Idea of the Teacher. University of Bookman, 01 Apr. 2013. Web. 04 Dec. 2014.