Descartes and Plato

EssayCompare and Contrast Essay
Jan 1, 2007

Epistemology is an important branch of Philosophy. Where Philosophy is the pursuit of knowledge and human excellence, epistemology is concerned with how we acquire and process knowledge. The study of epistemology is deeply related to our beliefs and ethics, which is what makes it important when writing essays about Philosophy . Plato and Descartes are two of the most well-known philosophers in the field of epistemology. They both presented the most elaborate theories of knowledge from which numerous other theories emerged. Although Plato and Descartes do not agree on the source of our knowledge, and in the process of ascertaining the truth of our knowledge, they agree in the need for critical thinking skills when evaluating knowledge and thus, our beliefs. In this term paper, the author will compare and contrast Plato’s and Descartes’ epistemology and analyze their continuous importance in Philosophy.

Both Plato and Descartes say that there is only one source of knowledge. And although humans have no direct access to this source, we are born with an innate knowledge of the world. According to them, humans’ understanding of the world, however, is distorted or limited by the world we live in. For Plato, he expresses this as the cave in the Allegory of the Cave, while for Descartes, it is simply our senses that may be deceiving us. According to Plato, the source of all knowledge is the True Good. True Good is where all things are based on. While for Descartes, truth and the pursuit of the truth should be based on ourselves, because it and God are the only ones that are without doubt.

Differences Between Plato And Descartes

Plato’s Epistemology

Plato’s epistemology attempts to understand what is means to know and how knowledge can be good for the person. Plato expounds on this in the Allegory of the Cave in The Republic . In the Allegory of the Cave, prisoners who are unaware of the Theory of Forms are chained to a cave and unable to turn their heads. Their source of light is a fire, and behind them is a puppeteer who holds up puppets to cast shadows onto the wall. The prisoners’ idea of objects is confined in what they see and hear from the shadows cast by each object. Thus, their image of the objects is inaccurate and possibly distorted. Furthermore, since they are unaware of the existence of the real objects, and have only seen the shadow versions, they would think that the shadows are real. Then, when one of the prisoners manages to escape and sees the ‘real’ world, he is blinded by the light coming from the sun. He struggles while his eyes adjust to the light. When it does, he realizes that the world he had known in the cave was full of misunderstandings. However, when he imparts this knowledge and attempts to free the other prisoners, they refuse and threaten to kill him.

Plato implies that we are like the prisoners—that the things we see in this world are not real, but are mere shadows of the real things. So, the names we use to refer to objects are names of objects we cannot see, but only grasp with our minds. Thus, knowledge of the empirical world alone is insufficient, as it is bound to be distorted. According to Plato, it is important to be aware that the things we perceive are not the same as their true form, that we are only perceiving shadows. In the allegory, the prisoner who escapes and learns about the truth represents the philosophers who seek knowledge outside of the empirical world.

Plato’s Allegory of the Cave is not meant to drive people away from empirical knowledge. Rather, empirical knowledge can be used as a bridge toward the pursuit of truth. So, empirical knowledge is not entirely useless or false. However, we must not be complacent with such knowledge. It must be understood as mere jumping point toward the truth.

What is most important in Plato’s allegory is the point that empirical knowledge, though it is based on seemingly concrete objects, is not fallible. These are shadows—mere reflections of the real thing, and thus can be distorted by our perception. Pursuit of the true forms, according to Plato, leads to the pursuit of the highest idea, which is the true form of Good. True Good is the source of all things and all knowledge. Thus, we pursue True Good with the help of our empirical knowledge.

Descartes’s Foundationalism

Descartes’ epistemology is called foundationalism. In the Meditations, Descartes claims that humans must doubt everything they were taught because of our tendency to believe what is false. He presents numerous basis for this claim. The first is because most of our beliefs is based on our senses, which are often deceived. He also believes that anything physical exists, and that we should only trust beliefs that uphold against rational scrutiny. Thus, according to Descartes, anything based on sensory-perception must be doubted. However, Descartes also claims that we must doubt even mathematical judgements as these could be lies concocted by someone evil. In fact, it seems that the only thing certain for Descartes is doubt itself. The only aspect of the world that Descartes does not doubt is oneself. Thus, the infamous quote, “ Cogito, ergo sum (I think, therefore I think I am).” So, according to him, we must build out knowledge based on ourselves. In his second meditation, Descartes explains that our knowledge is based on reason and not on sensory-perception. He demonstrates this through the concept of wax, which we identify as wax despite varieties in form, scent, and color. Our knowledge of things, such as wax, is to be able to anticipate its changes. However, this anticipation of changes is not the mere product of the imagination, for that would be unlimited. Rather, it is through understanding and reason. The third meditation is anchored on the existence of God. According to Descartes, God’s existence cannot be doubted for the fact that we have an idea of God verifies His existence. As such, there are facts that we know for sure to be true because they came from God. 

Comparison Of Plato’s And Descartes’ Epistemology

In this section, the author will compare and contrast the philosophies of Plato and Descartes. Plato and Descartes have different concepts for ascertaining the truth in the things we know. On the one hand, for Plato, we must seek the truth by basing it on our empirical knowledge. Plato acknowledges the limitations of the human mind in comprehending true forms, so we can only seek true good by building on empirical knowledge. On the other hand, according to Descartes, we must discard all our prior knowledge and beliefs and build true knowledge based on ourselves. Thus, their main difference is in their estimation of the human mind.

Despite these fundamental differences, Plato and Descartes somehow agree that there is a one true source of truth. For Plato it is True Good, which implies that to see the truth is also to seek good. For Descartes, the source of truth is God, who will not deceive us. This is, in fact, the main basis for his first meditation that we must base our knowledge on ourselves.


The most crucial similarity between Plato and Descartes’ epistemology, however, is their argument that we must not be complacent with the knowledge presented to us. We must examine their validity and to seek only truth. Regardless of their philosophies about knowledge and truth, both Plato and Descartes confirm the purpose of Philosophy to seek human excellence. Thus, in our pursuit of good and justice, we must always be vigilant and critical.

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