One of the first things beginning philosophy students study is René Descartes' Discourse on the Method. This document, published in 1637, is the source of one of the most famous phrases in philosophical history: "I think, therefore I am." In Latin, the phrase is Cogito, ergo sum. This phrase represents what is commonly believed to be one of the most important turns in the history of philosophy, and many people have heard the phrase even if they have never studied Descartes at all. Despite its fame, however, this phrase (commonly called "the cogito") is quite widely misunderstood.
What is an Argument?
Due to the way Descartes phrased the cogito, it's understandable that many people would mistake its ultimate meaning. In philosophy, the word "therefore" very frequently indicates a conclusion to an argument. A famous example of such a usage is in the syllogism. A syllogism is a type of deductive argument. Perhaps the most widely used example of a syllogism runs: Socrates is a man, and all men are mortal, therefore Socrates is mortal. This argument consists of three parts that make up the syllogism. First, Socrates is a man. This states that Socrates is a member of the class of men. Second, all men are mortal. This makes an assertion about the class of men. These first two parts are called the premises of the argument. Taking these two premises together, it is possible to conclude that, third, Socrates is mortal. The conclusion follows logically from the premises, and the conclusion comes after the premises.
Is the Cogito an Argument?
To summarize what has been said so far, in the usual form of an argument (1) the conclusion comes after the premises and (2) the word "therefore" is often used to indicate the conclusion. This is important to understanding why Descartes' cogito is so frequently misunderstood. If the phrase "I think, therefore I am" is understood according to the usual form of an argument, it seems that the premise, "I think" should lead to the conclusion, "I am" in a linear way. Understanding the cogito in this fashion has allowed philosophers to make many counterarguments against what they take to be Descartes' logic. However, the cogito is not meant to be a linear, deductive argument.
In Discourse on the Method, Descartes clearly states the cogito is not a deductive argument but is, instead, an intuition. This is crucial to understanding what Descartes means. To say that something is an intuition is to say that it doesn't follow a deductive structure, and we know it immediately, all at once. Often, the most basic mathematical principles are cited as examples of things that are known through intuition. For example, it is impossible to show deductively that 1 = 1. We just know, intuitively, that it does. The cogito is meant to work the same way. To take the analogy further, one might restate the mathematical principle as, "One, therefore one." If you try to understand that deductively, assuming that the "conclusion" comes after the "premise," you will be forced to conclude that the argument is nonsense. But, like the cogito, it's not an argument, it's an intuition.
"I think, therefore I am."
What, exactly, is Descartes' intuition, and why is it an intuition rather than an argument? This is a complicated question, but it's possible to understand it by considering the content of the intuition. Descartes claims to know for certain that he exists because he thinks. But the reason the cogito can't be an argument is that, in order to think, "I think," one has to already exist. So there's no progress from one thing to another, it all comes at the same time. The thinking and the existing happen all at once, rather than one after another. Just like the statement 1 = 1, no logical concluding is necessary; it all comes to us at the same time. That's why "I think, therefore I am," is an intuition.
The Cogito in Other Words
It makes sense to ask why Descartes would choose to phrase his intuition like an argument in the first place. Only Descartes could know the answer to that. Perhaps Cogito, ergo sum just had a nice ring to it. Sometimes, it helps to understand philosophical principles in different words, and this is one of those times. Descartes could have said, "I know that I am because I am thinking," or "Here I am, engaged in a mode of existing called thinking." However you choose to understand the cogito, take care not to fall into the trap of thinking of it as a deductive argument. The importance of the cogito to Western philosophy depends on its strength as an intuition, and when you understand it as an intuition you can have the intuition yourself, which will help you come to terms with the reason why this simple phrase has such great importance.