Plato’s Theaetetus

A very detailed blog on the text that brought about our current understanding of knowledge as requiring justification.

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It is in the Theaetetus that the JTB (justified true belief) definition of knowledge emerges, and the first attempt to arrive at a definition is found.

Protagoras

The sophist Protagoras of Abdera (490–420 BC) is brought up and discussed in the dialogue. Philosophers and sophists were both concerned with wisdom and knowledge, but their methods and motivations were different. Also, a significant point of difference between sophists and philosophers was that the former charged people for teaching the art of rhetoric to sons of aristocrats to excel in their political careers. They learned how to be more persuasive rather than learning how to discover the ‘truth’. The sophists were driven by interests, and philosophers by truth. Thus, the focus of their arguments was more on being persuasive than on being rational. Protagoras was a disciple of the pre-Socratic philosopher Democritus. Even though the later Greek philosophers have often not spoken very kindly about the pre-Socratics and the sophists, Plato talked about Democritus and Protagoras (and in some instances, Heraclitus) with respect. Protagoras is known to have written eight books. At that time, writing was an expensive activity. One had to be both rich and respected to write and be known for it. But for philosophers, respect was a tricky and fickle thing. In his work ‘On The God’, Protagoras says that he does not know if the gods were even there/existent. This made him unpopular amongst the Athenians, who called him ‘Atheoi’, which means one without god and is the root of the word atheist.

Attempts at Defining Knowledge

When Socrates asked him what knowledge is, Theaetetus attempted to characterize knowledge in multiple ways. His initial response was that whatever Theodorus (his teacher) taught (which was Geometry) was knowledge. Socrates replied that that is not what he asked — he did not ask what one may have knowledge of, but what knowledge in itself is, which is assumed by Theaetetus when he gives instances of knowledge. This was the first time in Western thought that the question of the characteristics and objects of knowledge was raised.

First Definition — Knowledge is Perception

Protagoras famously said — “Man is the measure of all things.” (‘Homo mesura’) This can, in a way, be understood as a doctrine of relativism. Here, the locus of truth is the subject. It can be taken to mean that each thing is how it appears to me, and for you, each thing is how it appears to you. For subject A, x could appear to be ‘a’, and for subject B, x could appear to be ‘b’. Both of these would be true as per this doctrine because ‘a’ and ‘b’ have, as the locus of their truth, individual subjects, ‘a’ is inherent in A and ‘b’ is inherent in B, and not in X.

Protagoras’ ‘man is the measure of all things’ is equated with Theaetetus’s proposed definition of knowledge — ‘knowledge is perception’ by Plato’s Socrates. Why? Because of their relativist nature. Theaetetus puts forward this definition and it is evaluated by Socrates. Note that here, perception (aesthesis in Greek) includes all five senses but primarily refers to the eyes and ears.

Relativism

To support Protagoras’ doctrine of relativism, perception has to be unerring (since it is knowledge). And since everybody perceives, everybody’s perception must be right, or true. For Protagoras, truth and perception, both have as their locus the subject.

But Socrates believed that while perception’s locus is the subject, truth value’s locus has to be the object. Object here means object of knowledge or eidos (which is episteme), and not empirical object, as that is not in the realm of Episteme (like eidos are).

The position of relativism holds two contrast positions as true. But Socrates did not believe in the truth of relativism. Definition cannot be relative. Eidos is not relative but is absolute. Eidos is not relative or dependent as it is self-dependent. Socrates wished to deny the relativism of truth because it could pervade beyond merely material (which is seemingly unimportant to him as it holds no serious consequences) to social, ethical and political matters (which could, on the other hand, have serious consequences). And, by nature, we are averse to some things. The thought that justice could vary if truth could vary seemed absurd and dangerous to him. The moment one accepts relativism, one rejects universality, reason and truth. Protagoras went on to deny the concept of logos/order itself. He believed instead in ‘nomos’ or human-made laws, as he believed that humans were the measure of all truth.

Suppose there is a knowledge claim about a thing X. X can be looked at in two ways. The Parmenidean way is to look at it as a stable being. The Heraclitan way is to look at it as a static becoming — an entity that is not yet ‘is’. Here, the notion of fire is also explicitly invoked to talk about change and motion. For Heraclitus, the soul can be equated with fire (and death with cold). Learning and studying are motions through which our soul gains knowledge. So here, the knower is the soul or the psuche. This understanding suggests that the soul itself is in the process of becoming, and that motion is good for the soul while rest is bad. It is important, again, to note that motion is not limited to the materiality of the world.

But if motion is the underlying principle then there can be no object or subject as there is no ‘is’ — everything is changing. If both the object and the subject are impermanent, how do we have perception?

Projecting Heraclitus on Protagoras, Socrates explores this definition in three ways:

1. The subject is in flux
2. The object is in flux
3. Both the subject and object are in flux

Perception is a relational product

The Greeks upheld the corpuscular theory, which is what modern science works with. For them, it was the Effluvium theory proposed by Empedocles. As per this theory, if a person perceives the color white in an object, the white is neither there in the object nor the eye. It is the result of the interaction of the eye and the object which generates minute particles called effluvia which are imperceptible themselves but are the basis of perception. Thus, this theory posits that there is some change through which this effluvium is emitted. This makes perception a relational product.

Let’s accept for a moment that perception is a relational product. And if perception is knowledge, then knowledge must also be a relational product. But what is it a relational product of? Through a Heraclitan lens, it has already been established that there cannot be a stable subject or object, as both are constantly in a state of flux.

The problem that Socrates was trying to raise was that if we are to accept what Protagoras said, we must accept that perception can never be erroneous. If we are to accept the Heraclitan understanding of the Protagorean definition of knowledge as perception, we must also accept that perception is a dual relational product and that knowledge and eidos/characteristics are all relational products.

An object O at time T1 generates a perception P1 for subject S. About this, the subject S makes a claim CP1. The subject S and object O both have changed as time changed from T1 to T2. Now, object O2 at time T2 generates a perception P2 for subject S2. The claim that S made for O, CP1, will not be valid for P2, as there is no continuity. S2 cannot say anything about P1. But even S cannot make a claim about O because the claim would need to be made after perception P which took place at T, at a time after T. Furthermore, for CP1 to be there, P1 should have been completed or ended. So, S cannot make a claim CP1 because time progresses to T2 and perception P is never completed. So this perception can be false, or rather, it cannot be claimed to be true.

Another flaw in this understanding of the definition is that it is not possible to make a judgment, because to do so, the subject must at least remain constant. But it is changing. Socrates’ suggestion that the subject is constantly changing latches on the belief that the subject is also an object. He aims to make being and becoming make sense together. Thus, if the subject is the object, as Heraclitus believes, then the subject is in flux too, ruling out the possibility of making judgements. To escape this, one has to show that the subject is not the object. But by default, one is one’s body, which is an object. So it has to be shown that the subject is more than the body.

What we understand from Heraclitus is that the body, which is confined to the material world, is in flux, but I am not confined to my body. This can be shown by showing that knowledge is not limited to perception. In Plato, we find the genesis of a very peculiar knower. The subject is the soul which mediates with the world through the body. So, eyes are not that with which we see but that through which we see. In the former understanding, we are limiting the subject to the body. In the latter understanding, the eyes are just a channel to the soul. The soul is an epistemic entity here. It is something that is not the body. It exists for the sake of knowing. Greek thought is not reductionist in the sense of reducing the soul to the body. The body, through its different sense organs, is only a means to perception. Then how can perception be knowledge? Experience demands something more than the body. The realization that to understand the knower is to understand the body is what gave rise to epistemology. Philosophers like Kant, in his unity of perception, Husserl, in his transcendental self, and Ponty, in his unified and embodied experience took this concept further and adopted different positions.

Objective and Subjective Relativism

Socrates talked about ‘objective relativism’, as per which both statements — X is hot and X is cold, could be held to be true, but here, the ‘is’ does not denote X as a being but as a continuum, or becoming.

Saying a sentence like ‘Maybe it is like a bird’ implies that there is a universal form of bird. Interestingly, this can be taken to mean that Socrates already had the notion of forms, the abstract idea that there exist universals, in his mind. Aristotle, in his Metaphysics, writes that Socrates can be credited with coming up with the concept of definition and universal, but did not separate them.

If, as per objective relativism, the object is always changing, then how can one make any meaningful claim about the nature of knowledge? Truth can only pertain to being or eidos, which is stable. Knowledge of a thing can be equated with knowledge of being, as it presupposes stability.

Since Heraclitus’ position is that of ‘objective relativism’, the characteristics of an object must not change until the object itself changes. But they do. For example, imagine a regular-sized glass full of water. It appears to have a lot of water until we place a very big glass of water next to it. Then, it appears to have a little. Another example could be that of beauty. One person might appear beautiful until an extremely beautiful person is standing next to them, making them look plain. In both cases, when the other object appears, the perception of the initial object changes even when it does not undergo any change itself. And both the judgements, before and after the other object’s appearance, seem to be true. This would mean that the characteristics of an object depend on the subject. But how can this be? It seems unacceptable, because if we accept it, we accept subjective relativism, as per which a subject can ascribe any characteristic to an object. Definition is not a predication. For an object that is stable at T1 and T2, characteristics cannot change, but we need to attribute change to claims about its characteristics. But we cannot violate reason, as we had earlier admitted. Even Theaetetus agreed that one who agrees with Protagoras’ position would have to accept this unacceptable theory, thus rejecting it himself. This is the demolition of the first defense of the definition that knowledge is perception.

The characteristics of more and less full, as in the case of the glass of water, are not given to us by perception. They come to use afterwards, when we perceive another object and compare. So, it cannot be a part of the object since it is not available to us when we perceive it. It is available when we think and compare. So perception is not knowledge.

Coming back to subjective relativism, characteristics must depend not only on the subject but the object. As per this, the subject-object dependency relation, if true, does not have the subject or the perceiver as the central entity, but the object. The perceiver is passive while the object is active. The subject only becomes active after receiving characteristics. So, during the production of characteristics, the object is active while the subject is passive. Though perception is a production, it is dependent on the object. The motion of the object is transferred to the subject. This is another understanding of the definition ‘knowledge is perception’, in which perception is dependent on and governed by the object and not the subject, making ‘objective perception’ knowledge, meaning that Protagoras did not mean that perception (in general) can never be erroneous. Socrates added that Protagoras taught this ‘truth’ only to his students.

But, to refute Protagoras’ claim that perception cannot be erroneous, Socrates put forward the following challenges:

1. Cases of misperception may be present when we are dreaming or are diseased. If such conditions exist, false perceptions might arise.
2. We do not have any evidence to affirm that we are awake and are not dreaming.

This seems like the anticipation of Descartes’ dream argument. One problem that lies in asking the question about which perception is objective perception is that it assumes that there is a perception that is not erroneous.

Even if one is able to save the ‘objective perception’ idea theoretically, how can one claim that their perception is objective? Additional questions arise — where one can place reality, in sleep or during wakefulness? Can truth be decided by the majority? Often, truth is determined by number and time, which seems absurd. This is why Plato did not defend democracy, because to make truth ‘true’, one cannot invoke number or time. In fact, that which is a true object of knowledge does not depend on whether one believes it or not. Objects of knowledge are independent of beliefs. Here, we can extend this understanding to Plato’s forms. Forms are eternal and are not mere assumptions.

The third problem with the first definition focuses on the subject — that the subject is also changing. The same object O can generate two perceptions for two different subjects, as perceptions are relational products. The knowing self is active. The same wine can be bitter to one while tasting sweet to another. This will mean that all perceptions are equally true/justified.

But a pig also has a body. If knowledge is perception which is limited to the body, then does the pig also have knowledge? It seems absurd to admit this. There is something peculiar to humans that is not there in animals.

Thus, there has to be something more to knowledge than the power of perception. But why is it that only man is the measure of all things and not any other creature? Also, if every person’s perception is equally legitimate, then why should one read Protagoras’ book? How does it contribute in any way? Therefore, there is something inherently wrong in Protagoras’ thesis. Aristotle talked about the bipolarity of perception. Perception is either true or false. It is not inherently legitimate, or else there would have been no need for learning. By believing that ‘man is the measure of all things’, one is removing the option of false by default, which defeats the purpose of teaching. So, the fault must lie within the subject as some subjects have faulty perceptions while others do not. The object must be stable.

The thesis ‘perception is knowledge’ changes to ‘seeing is knowing’. Socrates attempts to dismantle the relationship between knowledge and perception. This can be understood through an example. The first time that you perceived a pencil, did you know that it was a pencil? No, you needed to be taught that. Like Hume said — I don’t know when I perceive fire that it burns me. Thus, interpretation and understanding require insight or right thinking. This added element signals that there is more to knowledge than perception because insight is not a bodily function, it is the function of the soul. The soul is more than life principle, it is the knower.

Also, when you remember something you know, you are not perceiving it. Thus, knowledge is perception negates the possibility of gaining knowledge through memory. Giving up memory would be giving up temporality, which leads to denying the possibility of knowledge itself. We cannot confine knowledge to ‘now’. Thus, Socrates points out that we have to admit that perception is one thing while knowledge is another.

End of critique of the first definition of knowledge

The definition that knowledge is perception has been dismantled by showing that:

1. Perception is not always right
2. Knowledge cannot be a relational product
3. Objective and subjective relativist doctrine of knowledge are problematic
4. Knowledge cannot be limited to perception; memory and insight are essential to it

Through his critique of the first definition of knowledge, Socrates is highlighting the following two points:

1. He is trying to generate the idea of the knower as an entity not limited by the body (and hence perception). Even though this was touched upon by the pre-Socratics, it is Socrates who first makes this point explicit.
2. He emphasizes how the objects of knowledge are not just material but can go beyond the senses, or the materiality of the world. Thus, it is possible for one to grasp more than what can be grasped by the hands. It is important to note that ‘beyond materiality of the world’ should not be conflated with ‘beyond the material world’. That’s what Aristotle said, that Socrates did not go beyond the material world, only the materiality of the world. He believed that Plato misunderstood Socrates by positing the realm of forms.

Accounting for Error

In the epistemology of Western philosophy, theories of error are not seen. But most classical theorists are concerned with questions like — how do we account for error? Is the knower always in access to knowledge? What is peculiar to the knower? Is there a homogenous nature of the knower? Socrates’ main focus was to provide an account for the claim that perception can be erroneous.

‘Knowledge is perception’ can be taken as a relation of identity. Thus, if we have an account of how perception is possible, we should also be able to explain how knowledge is possible. As established, knowledge can be equated with Being, as both are stable and belong to the realm of episteme. Being is the highest form of eidos, which cannot be grasped by perception, as they are not material. Thus, perception and knowledge cannot have a relation of identity.

But establishing this is not enough as the error also needs to be explained. What is the source of the error? Is it the subject or the object? But the subject is also an object. As per Parmenides, what is, is. If the object ‘is’, then the error cannot be in the object and the material subject. So it must be in something abstract, something beyond. It must lie in the faulty insight or thinking of the subject. The process of thinking can be understood as ‘the soul talking to itself’. Thinking is that which mediates between the sense perceptions and the soul and leads one to become a knower. The product of this process is a judgment. Socrates then talks about the hierarchization of the epistemic subject. We already operate with this assumption, because if we did not, we would not have felt the need to read what thinkers like Socrates said. Thus, the question of ‘better’ or ‘worse’ men may arise if one believes the doctrine that man is the measure of all things. Passing a judgment is not a passive act but an active one. The subject is the one who does the thinking, so the error must also lie within the subject. Error can be accounted for if one recognizes the role played by the subject. Therefore, the possibility of being either true or false is inherent in the subject. In Euthyphro, Plato wrote that man becomes God when he becomes just and pious with understanding.

So, it has been established thus far that perception is inadequate for gaining knowledge, and that thinking or judging the object of perception for the evaluation of truth is required. What do you understand by thinking? Thinking is a conversation one has with oneself about one’s perceptions. The body is not responsible for the grasping of being, and thus has no share in grasping knowledge. This is the end of the demolition of the definition that knowledge is perception.

Second Definition — Knowledge is True Judgment

After the first definition fails, Theaetetus proposes a second definition. Knowledge is true judgment. But if one is to accept that knowledge is true judgment, how does one know when a judgment is true or false?

Since an object already ‘is’, there is no way to account for error through it. So the fault must lie in the subject. The subject’s mediation of the object through thinking (or judgment) must be wrong. If we are continuing with our Parmenidean notion of being and ‘is’, how can a false judgment give rise to something that ‘is not’. How can it not have an object? The resolution is that false judgements do have objects, but we judge them to be something else that is. This is why perception cannot account for error, because there is no difference between an erroneous judgment and non-erroneous judgment in terms of having an object.

Can perception’s locus be found in the body? Perceptions do seem to be limited to certain senses. But Socrates believed that confining oneself to perception will not account for even perception itself. What is one educating? It should not be limited to the body. Knowledge is found not in experience but in the process of reasoning about them. Parmenides said that quality must presuppose unity. Perception will never give one access to being, but only to particular bodily characters. Being is common to all perceptions but it cannot be known through perceptions. It requires one to go beyond. In modern philosophy, the distinction of substance and quality is similar to this. This was brought up by Descartes in the mind/body identity relation, in which the mind cannot be equated with the body as the body is essentially in space while the mind is not. Perception itself cannot be confined to the body because, without something else, you cannot have a synthetic unity of experience. To understand this, think about two different perceptions — the sound of a glass falling and the sight of it. Even though they are different in perception they make up the same experience.

The role of perception ends when one has to arrive at a judgment because perception is confined to its own different particulars and passing a judgment would involve something more. If asked to judge which glass has more water, I would need to compare the two individual particulars. This comparison is made possible through thinking, which is different from perception.

Knowledge is necessarily definitional. Perception can only give one knowledge of particular instances. But knowledge is not about particulars. It has to rise beyond. This can be understood as pointing towards the eidos. That is perhaps what Plato meant when he said that one should look through the eyes of the mind or the soul. The soul functions through a power that is peculiar to it. This is the ‘thinking function’ which is present in the thought of Heraclitus and Parmenides as well. Two aspects of it need to be understood:

1. It cannot be located in perception
2. We cannot elaborate perception without it

When we perceive a red crayon, do we perceive it as red? The idea of redness is necessary and we are only aware that the crayon is red, or that it even is a crayon, after we have mediated our perception through thinking. This signals a move towards the abstraction of forms.

Knowledge of categories is necessarily presupposed by any judgment that individuals experience. The most fundamental category is that of Being/is, as all ness-es but be. For perception to be possible, one needs to already have some form of knowledge/characterization. This knowledge is central as it makes decisiveness about other knowledge possible. Here arises another problem. How do we get this knowledge? One solution is to claim that this knowledge is innate. This is what Plato expresses in Meno, that the soul already knows. But there are problems with the innate knowledge doctrine. Why do we not know when we are born? Why do we not have homogenous cultures? These have been raised by philosophers like Russell and Locke. In Theaetetus, this problem remains unresolved.

Socrates believes that we must differentiate between ‘possessing’ and ‘having’. Socrates gives the famous aviary example here. You possess the birds in the aviary, but you do not have them, as you are not necessarily in control of them. Interaction should not be conflated with subjugation.

As discussed above, because an object already ‘is’, there is no way to account for error through it. So the error must lie in the subject. This gives rise to the paradigm of objectivity. As per this, the error lies within the subject. To judge is to make a statement to oneself. ‘Something I know’ can be equated with ‘eidos’. The fault cannot be in the object, or in the eidos that one already has. The only way to account for error is by examining the nature of the soul that is accessing the eidos. The judgment is false if one cannot access the eidos. Thus, account for error is essential in determining if the judgment made is true or false. So the second definition of knowledge is inadequate.

Third Definition — Knowledge is True Judgment With An Account

The chain of thought leads Socrates to the third definition of knowledge. Knowledge must be a judgment that is true, and we must be able to account for it. True judgment mediated by thinking (which requires the lens of eidos and is a function of the soul) and an account of having arrived at the judgment is needed if one is to claim to have knowledge. Since truth ‘is’, it can be equated with being (in the same way knowledge can be).

Eidos cannot be provided to us by perception. Our souls are already imprinted upon by eidos. You cannot be a creator of eidos and can only be a discoverer, as eidos is presupposed for there to be an epistemic knower and for there to be order in the cosmos. If there is to be knowledge, there must be eidos, which is ‘being’. On equating eidos and ‘being’, we can equate their characteristics also. Eidos is ‘given’ and is uncreated. Plato never makes Socrates explicitly talk about the Theory of Recollection, rather, he hints at the theory by making him say that he has heard so-and-so from ‘wise’ people. Meno provides us with the theory of recollection which is an attempted solution for the prior demand of eidos, as per which we have both active and passive memories. The soul possesses but does not have eidos. The moment it has eidos, it has knowledge. Plato claimed that when one does have access to eidos, it will be so self-evident that they would not require justification. Heidegger’s Alethea (self-evident truth) concept seems to be inspired by Plato. This understanding leads to one problem — one needs to have knowledge to create definitions but definitions require one to already have some eidos.

In Plato’s thought, what is open for argument is one’s clarity in accessing eidos. (The modern-day term for ‘eidos’ is ‘a-priori’.) But what is not open for argument is the presence of a-priori and innate knowledge. How does the soul already have eidos? We do not know. The theory of recollection is just one attempted solution to explain their innateness. It can be denied. But the prior demand for eidos in the soul cannot be denied. Even Descartes had to accept innate ideas because he realized that without them, the epistemic enterprise has no foundation. But we are still unable to provide an account for the innate knowledge of eidos. The role of the account is to show that the judgment is made in line with the eidos. In other words, this account would disclose that this judgment aptly grasps the eidos on which it is based.

Plato, through Socrates, points out the flaws in the JTB definition of knowledge. If knowledge is a true judgment with an account, that account itself needs to be true and have a justification, ad infinitum. This infinite regress arises because accounts require justification. Keeping this infinite regress aside, the third definition of knowledge is accepted, but what counts as an account is still not clear. For example, love is the greatest emotion, but how do I define love? But just because I cannot account for it, or define it, does not mean that I will discard my hypothesis or claim of knowledge. Thus, Socrates arrived at a definition of knowledge, but he was not able to give an account for its account. Aristotle, through his deductive syllogism, believed that he had solved this problem.

Theaetetus — Takeaways

The takeaways from Theaetetus are:

1. If you want to define knowledge, you must accept that there are prior elements of knowledge that you possess
2. Perception can be erroneous
3. The soul is more than the body

The Greek thinkers believed that the cosmos must have a principle of order. Most of the pre-Socratic found it in material elements. Plato found it in eidos. He believed that there is order in the world because of eidos. Plato emphasizes that we have to understand that we must have a soul and that there is a demand for eidos.

Theaetetus — Additional Things

For a change, Socrates’ interlocutors in Theaetetus do not readily agree with him, and he is required to put in more effort to prove the efficacy of the Socratic method.

Plato’s Socrates, in Theaetetus, proclaims, at a point, that gender is of no relevance to a philosopher. In Plato’s Republic, the possibility of females to be the Philosopher King is not ruled out. Labelling all of philosophy as being patriarchal would be an oversimplification. If we take the example of Plato, we can see both sides — a pull of the current, dominant (for him) patriarchal tradition and the older, matriarchal tradition. This (being more conscious of the context in which a philosopher thought) would help expose hidden nuances in their work.