What Did Descartes Mean With “Cogito Ergo Sum”?

‘Cogito ergo sum’, or ‘I think, therefore I am’, was René Descartes’ most famed maxim. But what did he really mean?

Aug 24, 2023By Luke Dunne, BA Philosophy & Theology

cogito ergo sum rene descartes


“Cogito ergo sum” is a Latin phrase that translates to “I think, therefore I am.” It was coined by the philosopher René Descartes, a French thinker who is seen as the first philosopher of the modern period. René Descartes introduced this famous statement in his work Discourse on Method, a work which Descartes published in 1637. In this work, Descartes set up to explain some of the fundamental principles of philosophical enquiry.


Descartes Argued That We Should Be Skeptical 

Portrait of René Descartes, Pieter Nason, 1647, Agnes Art Center


Before we get into the details of what Descartes meant by “cogito ergo sum”, it is important to recognize that this idea – which is really just a very brief argument or assertion – comes up in the context of Descartes’ skepticism.


Descartes is known, above all, for his method of doubt. He wanted us to throw all of our beliefs into question, and to allow for the possibility that everything we think we know is wrong. This move in Descartes’ philosophy has proven to be enormously important to the history of philosophy. Some philosophers still don’t think we have a good answer to the skeptical worries Descartes articulates. Descartes begins his philosophical enquiry with doubt, and by asking what the limits of our capacity to doubt are. In other words, he wants to know what it is that we cannot doubt.


Descartes claimed that he doubted everything he had learned throughout his life, including the information acquired through the senses, the reliability of his own perceptions, and even the existence of the external world.

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Descartes Believed We Should Value Thought

Dream, Think, Speak, Christopher Le Brun, 1982, via Tate


This is where “cogito ergo sum”, Descarte’s famous quote, starts to come in – we can doubt many things, but we cannot doubt that we think. After all, even doubting is a kind of thinking. “Cogito ergo sum” is, for this reason, a fundamental element of Descartes’ philosophical method. This method aimed to establish a firm and indubitable foundation for knowledge. Descartes realized that he could not doubt the act of doubting itself. Even if he was being deceived (or, as Descartes puts it, being misled by some kind of evil demon), there had to be a thinking entity (in this case, himself) that was being deceived. In other words, he found it impossible to doubt the existence of the “I” that was doing the doubting.


We Should Trust That We Exist

René Descartes, Frans Hals, 1649, via Wikimedia Commons


Descartes famously concluded that the act of thinking, or the process of doubt itself, was evidence of his existence. In other words, Descartes doesn’t just think that we are capable of thinking. He also believe that, by virtue of our having the ability to think, we can also justifiably claim to exist.


In his own words, he wrote: “Cogito, ergo sum” or “I think, therefore I am.” This “I” or thinking entity became the first indubitable truth in his philosophical system. That means that his denial of doubt became groundwork – the basis and justification – for his subsequent attempts to build on a solid and certain foundation.


In other words, Descartes wants us to trust in the power of thought to allow us access to truths about the world. This makes “cogito ergo sum” an epistemological argument – one which is concerned to make a claim not just about how things are, but about how we know them to be that way.


We Should Build On His Work

Building Site Oxford Street, Leon Kossoff, 1952, via Tate


Descartes focuses on doubt in a single-minded way precisely because he is attempting to lay the groundwork for a philosophical understanding of the world. The purpose of focusing on doubt in particular is to free us from the skeptical worries which he himself was plagued by, and thereby give us space to philosophize more boldly.


For Descartes, the purpose of “cogito ergo sum” was to restore our faith in the power of thought, and in our right to build systems of thought using reason. Descartes as a rationalist – one who believes knowledge can be deduced, rather than acquired from experience – and so for him a defense of the power of thought was of the utmost importance.


In conclusion, Descartes’ “Cogito” has had a profound influence on the development of modern philosophy and in particular epistemology, which is the study of knowledge. It remains one of the most well-known and debated philosophical ideas today, because it captures a very influential response to the problem of doubt in philosophy.

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By Luke DunneBA Philosophy & TheologyLuke is a graduate of the University of Oxford's departments of Philosophy and Theology, his main interests include the history of philosophy, the metaphysics of mind, and social theory.