Philosophy can be defined as the systematic pursuit of knowledge and human excellence. This paper looks at the differences between Descartes’ epistemology in Meditations on First Philosophy and Plato’s in The Republic.
Descartes’ epistemology is known as foundationalism. In the Meditations, Descartes doubts everything he was taught to believe because it is human tendency to believe what is false. He claims that most of what he believes is from his senses and that those senses are sometimes deceived. His solution to doubting everything is compared to a basket of apples. You fear that some apples have gone bad and you don’t want the others to rot, so you throw all the apples out of the basket. Once this is done, you examine each one and return the good apples to the basket. This is what he does with his beliefs. He keeps only those he truly believes in. We must discard our beliefs as a whole and then examine each one individually. We must build on the good beliefs. Descartes, nevertheless, realizes we can’t throw every belief out because they are a part of us. If we throw away everything, we would have no basis for recovering any of our beliefs. As a result, we would not be able to justify anything.
No belief based on sense-perception is free from doubt. According to Descartes, it is possible that life is all a dream and we are being deceived into thinking it is reality. He also holds false anything that is physical exists, including his own body. The only things we should trust are those beliefs that are subject to rational scrutiny. We must also declare our mathematical judgments to be false also because an evil demon might be deceiving us.
Now, Descartes doubts everything else except himself. He cannot be deceived about himself. It is on himself that he will be able to rebuild his knowledge of other things. If he had no knowledge of himself, then nothing can be certain. If he doubts, he must be an existing self which is engaged in doubting. If he doubts, he must also be thinking and Descartes said “I think, therefore I am.” Descartes states that his doubt in his sense and what he has been taught to believe in has ultimately resulted in him believing in himself. It is not possible to have no beliefs therefore Descartes, who doubts everything else including his existence, only believes in himself.
He must also exist so that he can be deceived. If he is dreaming, then he is also thinking, thus he still exists. This is the first step to acquiring knowledge, according to Descartes. You must build on what you know is certain, starting with yourself as the foundation.
In the second meditation, Descartes tries to show we know bodies through reason and not through senses. He uses a piece of wax to demonstrate this. Over a period of time, a freshly produced piece of wax placed by the fire loses or changes all its specific properties, yet it is known to be the same object. Its taste and odor disappear. Its color, size, and shape are completely transformed. It loses its hardness and coldness to liquidity and warmth. To know the wax, you must be able to anticipate its changes. Descartes argues, though, that the imagination could not possibly figure out all conditions, for they are infinite. One can only know an object through understanding, rather than through images, sensation or imagination. He now has knowledge about himself and any object that he has thought about through reason.
In the third meditation, Descartes, develops another building block of knowledge, God. We look at the example of two plus three equaling five. We see this to be clear and distinct, but there is a possibility that we are being deceived. He tries to dispel the doubt about propositions of mathematics by claiming that God exists and would not allow such a deception. He makes an argument for God’s existence. The basis for the existence of God is that we have an idea of God. The second basis is that the only way to have an idea of God is if God exists. Therefore, the conclusion is that God exists. Us having an idea of God mean us having an understanding of the infinite. We can’t understand the infinite through the finite, but only through the infinite, thus God must also be the cause of the idea of God. We as finite substances cannot cause the existence of an infinite substance. The idea is also an objective reality, thus it can be held as true. God is not deceiving us and now we have added the final building block to our house of knowledge.
In The Republic, Plato has his own epistemology which is based more on idealism. As opposed to Descartes, Plato believes that ascent to knowledge is not based upon understanding an object, but understanding the idea of that object. The highest idea or form is the idea of the Good itself. Socrates is the main character of this section of The Republic. He engages in a conversation with Glaucon about knowledge. Socrates gives two images of the ascent from chaotic opinion to orderly knowledge, the image of the divided line and of the Cave. Knowledge is what is certain and true and opinion is what is fallible. This is where we may see a connection between Plato and Descartes. They both agree that knowledge must be certain and all other things false.
Plato held that all knowledge can be derived from a single set of principles. Knowledge rests on the Good as its foundation, unlike Descartes, where one’s self is the foundation. Plato compares the power of the Good to the power of the sun. The sun illuminates things and makes them visible to the eye. The absolute good illuminates things of the mind and makes them intelligible. According to Plato, the idea of the Good is too much for humans to understand, but can be thought of as the idea of absolute order. The sun is the cause of generation, nourishment, growth, and visibility. The Good is the cause of essences, structures, forms, and knowledge. This is somewhat similar to Descartes because God is the cause of the idea of Himself, thus the cause of everything else also.