25 de jul. de 2023

On episteme and theories of knowledge - by Plato


Episteme has Greek origin; means knowledge. In the course of history, different ways of explaining how knowledge was given or constructed in human everyday life emerged. In our work, whose proposal is an overview of the theory of knowledge exposed in the dialogue between Socrates and Theaetetus, written by Plato, we will primarily consider Platonism and empiricism, two diametrically opposed epistemological forms. Nevertheless, we will proceed with a brief analysis of the philosophies present in that text.

knowledge theories

Knowledge, for the Greek philosopher, is contemplation; it is theory, not intended to change the nature or reality of anything. However, we noticed that, in the text we studied, there are three definitions of knowledge that are worked on in the dialogue between Socrates and the young Theaetetus. In the conversation, Socrates uses the technique of irony by reduction to absurdity to convince Theaetetus that only one of the three proposed theories is true. He uses the argument contrary to what he defends to prove it weak and unsustainable. During the conversation, Socrates passes himself off as a person who accepts Theaetetus' arguments; however, in the course of the dialogue, he begins to show the weaknesses of the young man's propositions, even placing them as absurd. With this method, Socrates inaugurates “negative knowledge”, that is, knowledge based on what it is not, as we will approach in our work.

The three definitions of knowledge are:

Knowledge is sensation: in this definition, we clearly see that knowledge is based on experience, as it is the human senses that provide information in the foreground. Socrates argues that people's senses are different and therefore subjective. Furthermore, people's perceptions can change with age and time, making this knowledge unreliable. Furthermore, the wind that hits people, in any weather, anyway, can be cold for some of them and hot for others, a conclusion that does not contribute to a universal knowledge about what wind is. In this way, the subjectivity defended by Protagoras and the mobilization defended by Heraclitus are denied by Plato, as we will better exemplify later on.

Knowledge is the decomposition of the object for analysis: this is, without a doubt, the main defense proposition of empiricism, because, for a better analysis of each structure, each scientist, from each area of ​​knowledge, decomposes the object until looking for its particular. In this particular would reside the idea of ​​what knowledge is. This is another definition contested by Plato, who seeks exactly the opposite: a universal, immutable and eternal knowledge.

Justified true belief: in this third definition of knowledge, defended by Plato, the idea is worked that knowledge must be accepted within the society where it exists. Beliefs are beliefs held by groups of people because they are based on values, customs, and habits of those groups. We then infer that knowledge, to be true, within this conception, must be believed in the light of some criterion that is accepted by all. In this way, yes, according to Plato, one can build knowledge capable of transcending the particular and time, capable, finally, of reaching the intelligible.

Proposal by Plato and his competitors

Knowledge in Plato is linked to the conception that the real world is the world of ideas, in which sensible experiences have no real importance because they are subjective. The ideal (universal) is in fact, in Plato, the real. In this real, knowledge would be valid for all entities. On the contrary, the empiricist sees the universal as a non-existent thing; flatus vocals. Their belief is based solely on the existence of particulars. For example: while Plato would point to the universal concept of a table, worrying about the general characteristics belonging to all tables, that is, tables with three legs, with four, with two, made of wood, glass or plastic..., empiricists would be specifically concerned with the particularities of each one of them. There is not, for those concerned with particulars (the empiricists and the nominalists), a common table concept. They are concerned with the characteristics that make each entity different – ​​the tables with three legs, with four, with two, in wood, glass or plastic...

Plato's goal is the soul, as he believes that the world the body is in is a theater of leftovers. While we look at things and deceive ourselves, we can close our eyes and turn to ourselves, to the soul – where, for Plato, reality is. He points out that it is necessary to abandon, therefore, the sensitive, the experience. In Platonic philosophy, the soul is knowledge, as it is based on universal aspects, while the body would be the doxa (i) (what they talk about...).

For Plato, reason leads to knowledge of the intelligible. This statement demonstrates, above all, the need for man to be equipped to deal with his own wonders, wonders. Otherwise, the will never be able to leave the world of the sensible. In the painting, we perceive the intelligible as a point to be reached by the philosopher. Thus, reason would be in control, as emotions only concern what is lowest in man, farthest from the reflection and knowledge of the soul. We then realize that knowledge, for Plato, is knowledge of the soul; it is contemplation itself that denies experience.

Plato was an outspoken critic of empiricism. In Theaetetus, he frames Protagoras as an empiricist, as he states that “Man is the measure of all things” (Homo Mesura).

THEAETETUS - (...) It seems to me, then, that whoever knows something feels what he knows. So what seems to me at this point is that knowledge is nothing more than sensation.

Socrates – (...) Perhaps your definition of knowledge has some value; it is the definition of Protagoras; in other words, he said the same thing. He claimed that man is the measure of all things, of the existence of those that exist and those that do not (Plato, 1973, p. 32).

There is a big problem, as Socrates comments, in this proposition: do we speak of man as an individual or of man as a species? If we admit the first hypothesis, we fall into subjectivism, in which there is no universally valid truth. As a species, we would neglect the existence of everything else. Still, relativism, which is also present in this issue, would call into question the qualities present in statements and propositions. This relativism that we commented on can be divided into three forms: the cognitive, which concerns perception; the ethical, which points out what is correct in each social formation; and the cultural, in which an object changes importance according to custom (custom is king).

Plato cannot accept these propositions, since his search concerns, mainly, the search for a universal truth, present in all beings; therefore not subjective, not relative to something else. This universal is immutable, it cannot be in transformation or in movement, which makes Plato oppose subjectivism, relativism and mobilization, the latter considered a plague by him in Hellas: “‘If something is at a certain moment, it ceased to be so at another moment”. With that statement, Panta-Rei, who has an identity now, will not have it a few seconds later. With mobilization, everything is in an eternal flux, process, in progress towards something, in an eternal becoming, in an eternal movement. As these transformations are impossible in the world of ideas, as they cause transformations, different representations of the same event, doxa (i), different sensations, Platonic philosophy becomes impossible.

From the translation of things, from the movement and from the mixture of one thing with other things, everything that we say exists is formed, without using the correct expression, because strictly speaking nothing is or exists, everything becomes. On this, with the exception of Parmenides, all the sages, in chronological order, agree: Protagoras, Heraclitus and Empedocles, and, among poets, the highest points of the two genres of poetry: Epicarmus in comedy and Homer in tragedy. When he refers – to the father of all eternal gods, the Ocean, and to the mother, Tethys, he implies that all things originate from flux and movement (Plato, 1973, p. 33-34).

In subjectivism, the truth is present in each individual. Socrates, by claiming that he knows nothing, uses a fallibilist stance to refute arguments based on empathy, subjectivism and becoming. It points out that we cannot be absolutely sure of anything. Irony, a demonstrative method used to dismantle the arguments of those who presume to know, bringing up belief without reason and lack of foundation, appears in this excerpt from the conversation between Socrates and Theaetetus.

Socrates – So, tell me, once more, if you accept that nothing exists and that everything is in a perpetual becoming: the good, the beautiful and everything else that we have just listed (Plato, 1973, p. 42).

Socratic irony aims to overthrow baseless beliefs, as we have already pointed out. He builds his knowledge through the elimination of errors, that is, in a negative episteme that seeks to learn by eliminating errors. Thus, each and every theory is fallibilist, that is, it is neither eternal nor fixed, and may fall at any moment.

Furthermore, there are forms of knowledge that are more valid, legitimate and of better effect than others, even if we are not absolutely sure of them, even if the method to approach it is based on not knowing, on what we know it is not. He speaks of the universal, of the common to all. As we pointed out, the prepared philosopher must use reality with the perspective of facing pure, eternal forms.


We can compare the Platonic proposal of knowledge through the world of ideas with the philosophical proposal of episteme, in which the philosopher would dedicate himself to a vision of the truth of the whole. In this way, declarative, imperative, prescriptive, interrogative, exclamatory propositions, among others, created by philosophers would lead to the various isms created to explain the world in which we live. These are the philosophical schools, characterized by being all closed systems of ideas that aim to explain the world, such as existentialism, Marxism, Aristotelianism... and Platonism itself.

On the other hand, the connection between empiricism and modern sciences is also clear, in which experience is the last word in the construction of truths. Although all knowledge moves towards explanatory unification, science branches out into several areas of activity, pointing to different answers to the same questions.

It should be noted here that the definition of knowledge as articulated true belief or justified true belief is the most accepted, both by philosophers and by scientists today.


HESSEN, J. Theory of knowledge. Coimbra: Successor, 1973.

PLATO. Dialogues, volume IX – Theaetetus – Cratylus. Belém: Federal University of Pará, 1973. Amazon Collection.

OLIVA, Alberto. Theory of Knowledge I classes, in the 1st period of 2007. Rio de Janeiro: UFRJ/IFCS, 2007.


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