Tag Archives: epistemology

哲學功課: Cogito, ergo sum

The Cogito is the short form of “Cogito, ergo sum” in Latin, which means “I think, therefore I am” in English. The Cogito is the most famous quote from French philosopher Rene Descartes (1596 – 1650). Contrary to popular beliefs, the phrase “Cogito, ergo sum” is not used in his most important work, Meditations on First Philosophy (1641). This phrase is found in his earlier work, Discourse on Method (1637). However, Descartes offers the clearest explanation of the Cogito in the Meditations on First Philosophy. According to Descartes, the Cogito, awareness of one’s own existence, is the first secure step in the path to knowledge. The idea of the Cogito is Descartes’ solution to the problem of epistemology. He wants to show that we have foundations of knowledge by using the method of doubt. He keeps rejecting all the beliefs that are not absolutely certain, until he arrives at the one certain and unshakeable idea, which is the Cogito.

Descartes starts his inquiry about the true nature of knowledge by systematically questioning all his prior beliefs. First, he concludes that knowledge deriving from senses is not reliable. Human senses are prone to error from direct and immediate observations. A different answer often surfaces when the object in question is examined in further details. Second, he argues that we are not able to distinguish the real world from dreams. Descartes does not satisfy even if he has a clear understanding of the world through senses. He questions the existence of the world that he senses. Therefore, we cannot rely on any knowledge based on the observation of the external world. After all his briefs are filtered by these two powerful doubts, only abstract knowledge, namely mathematics, exists in his mind that remains trustworthy. At this point, Descartes takes another step and introduces an additional twist to his arguments. He claims that an evil demon may exist that aims to deceive him continuously. As a result, he cannot even rely on the truths coming from reasons, as well from experience. In this thought experiment, Descartes successfully falsify almost all his perceptions, except the Cogito.

Descartes asserts that although he no longer knows what is absolutely true, he cannot falsify what he seems to perceive. He knows that he is a “thinking thing” through the fact that he is thinking, doubting, understanding, affirming, denying, willing, refusing, perceiving senses and having mental images. This fact is the light at the end of the tunnel in his quest of knowledge. He cannot deny his own existence even with the three stages of doubts: senses, dreams and evil demon. He argues that he knows with absolute certitude that he has conscious experiences and thus he exists. Descartes used the phrase “I am, I exist” to conclude the proposition of his thought experiment. Ironically, even though this phase is more precise, it is not as remarkable as the phrase “I think, therefore I am” used in his earlier work. Thus his train of thoughts is often known to later generations in the form of “Cogito ergo sum”, which gives the Cogito its name.

It is important to point out that the Cogito can only be understood from the first-person perspective. We cannot consider the preposition of “Descartes is thinking, there he exists” is valid. Each of us should follow Descartes’ foot steps individually and formulate the arguments outlined in the Meditations I and II to convince ourselves that we really know that we exist. Once the proposition of “I exist” is understood, it can be served as the foundation for the rest of our knowledge.