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Descartes: Cogito ergo sum; I think therefore I am ... what does it mean?

Updated on June 29, 2011
rene descartes
rene descartes

Cogito or Cogito ergo sum, is the Latin translation for Descartes famous claim ‘I think therefore I am.’ This is a pivotal part of the argument for existence that he gives in the Meditations. It is the first thing he says we can know for definite after doubting the existence of everything else. He says we must doubt everything because there is a chance that we are all being deceived by an evil demon so everything we believe to be true could just be an illusion. But it doesn’t make sense to say that we could be deceived about the way we think. The fact that we can have thoughts about the state of the world (regardless of what we doubt) means that there is some ‘I’ that exists. Perhaps there is an evil demon making us believe in a false reality, but there must be something in existence that the demon is manipulating. This is the thinking thing that Descartes calls ‘I.’ The claim ‘I think,’ or ‘I am thinking’ does not require us to have any knowledge or evidence of the world. It is not based on anything else; therefore it does not rely on the truth of a claim that could turn out to be false. From here, Descartes goes on to affirm the existence of God, as he knows his beliefs and thoughts are real (even if they are not true).

discourse on method and meditations
discourse on method and meditations

The Cogito can only assure Descartes of his own existence, not the existence of anyone else, and we can only use it to know of our own individual existence. This is because we can doubt the minds of other people and the existence of their thoughts. Similarly it can only verify our existence at the point in time when we declare ‘I think’ because anything in the past ‘I was thinking’ or the present, could be something the evil demon has deceived us on. There has been much debate over what Descartes means when he uses the word ‘think.’ Many people question whether this means understanding, reason, intellect etc and think that if it includes these then there is a problem with Descartes reasoning. Personally I think that when Descartes says ‘I think therefore I am’ he is referring to anything that we do that does not involve the existence of something else. For example, we can use reason and intellect a priori; without having to learn anything first or relying on some other concept. I think he also means anything that we can believe without implying a contradiction. It cannot for example, apply to memories, as they rely on an event in the past which we could be being deceived about.

Many people argue that ‘I think therefore I am’ is analogous to saying ‘I am walking therefore I am’ but I disagree with this. My interpretation of it is that Descartes is saying I think therefore I am a thinking thing. From saying that ‘I am walking …’ I can only claim the existence of a walking thing, not a thinking thing and even that can be called into doubt. You cannot claim to exist on the basis of walking because you could be being deceived into believing you had legs or you could be dreaming that you were walking. The only things you can be sure about are events that do not require any interactions to have taken place.

People also claim that Descartes is making a jump between thinking taking place and the existence of ‘I.’ They say that just because there is the existence of thought that does not mean he can conclude that it is he doing the thinking. I am inclined to disagree with this argument. Surely, as I have just said “he can conclude …” it has implied that there is some ‘I’ in Descartes that has allowed him to make this conclusion. The critics affirm Descartes existence whilst at the same time try to argue that he cannot be sure that he exists. A response to this would perhaps be that in the premise of the argument; ‘I think,’ Descartes refers to ‘I’ which he then proves in the conclusion. This is what is known as a circular argument as he uses what he is trying to prove in the premise. It is a fallacy that often occurs in arguments to proving the existence of God. Many would say that this makes the whole argument invalid.

So, to sum up: the Cogito (I think therefore I am) is the first piece of knowledge that Descartes can be certain of. It is highly important in the formulation of the rest of the Meditations. There are interpretation issues over pretty much every part of the Cogito; the use of ‘I’ in the premise and the scope of ‘I think’ being the main ones. I like the Cogito and to me it seems to make a lot of sense and appears fairly self-evident. When I think about things, or I put my thoughts into this hub I am convinced that it is my own capacity and ability to think that is allowing me to do so. However, I do wonder about the usefulness of the Cogito. All it can tell any one person is that they exist at one specific moment in time. It cannot relate to a third person and it cannot relate to the past or the future.


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    • profile image


      6 years ago

      These pieces really set a standard in the insutdry.

    • HeavyDosage profile image

      Jason Link 

      8 years ago from Berlin, Germany

      Sorry.. to elaborate:

      I've always been interested in this notion by Descartes. I really get troubled when people refer to the Matrix to communicate this idea, because I worry that people will have a very limited understanding as to what it means "to be." However, if anyone is interested in watching other movies about the veil of reality, and the possibility for deception, you can watch (as well as "The Matrix"): "eXistenZ" (1999) and "Inception" (2010).

      Now, the reason that it bothers me how people reference these movies is that it gives others a liminal understanding - they lose touch with the idea of Dualism. Certainly this idea can hold water as an interesting notion if you consider our deception to be a matter of "what reality we really are perceiving" (a la Matrix's cyberpunk reality being a world that physically exists, but we are unaware of it because of our senses being manipulated). However, people lose touch with the fact that the 'real world' in this case is really a similar notion to that infinite and Eternal "I AM" that is God.

      The point is that Descartes' statement in no way ratifies the existence of a physical reality, but only confirms the very existence of oneself. It is totally separate from any notion of a physical reality. Interestingly this idea is often ignored by those who advocate the absence of an existing God - namely because they consider 'physical' proof and not epistemological proof to be the basis for this kind of argument. This discussion further limits itself in the constraints of a "Christian God" or any popular manifestation of one, as opposed to the idea of spirituality in itself.

    • HeavyDosage profile image

      Jason Link 

      8 years ago from Berlin, Germany

      "And God said unto Moses, I AM THAT I AM: and he said, Thus shalt thou say unto the children of Israel, I AM hath sent me unto you."

      Exodus. 3:14 (King James Bible)

    • jenblacksheep profile imageAUTHOR


      9 years ago from England

      But if we were in the Matrix then you would "think" that it was real, you would be convinced that it was real. But if you were taken out of it and then given the option of being plugged back in (and forgetting it wasn't real) or living in a 'less good' real world, which would you choose?

    • profile image

      Park, Jae Kyung 

      9 years ago

      In my opinion, the reality is that we are living. It means we can hear, smell, touch, taste, see, and think. If we are thinking, we are living. If this is not real, then I will ask to myself "What is real? What will happen if we discovered the truth?". I believe we can live even if it's not real because we "think" we are real.

    • profile image

      lar and asr 

      10 years ago from Cathedral city, CA

      You think therefore you are, for there to be thought there neeeds to be one thinker(minumum) and you can create new ideas so you are at least one of the thinkers there might be no others but you though according to me you are a possible illusion


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