How does Descartes say a thought necessarily means there is a thinker? In my opinion, "I think therefore I am" is egocentric because could really stem from an illusion of the thoughts belonging to an owner, and I don't really see why a thought couldn't exist on its own? It may be the definition of a thought but that's just semantics, isn't it?

It sounds like that's what this question was trying to ask but was misunderstood because the "I" in "I think" seems so intuitively obvious.

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    Not sure. But if "I think therefore I am" was an illusory thought belonging to a different entity than the "I", has not the "I" still come into existence within that illusion? Again... not really sure about this one. But if I as a thinker am able to create something that is capable of thinking "I think therefore I am", is not that something worthy of the title "I"? Commented Dec 27, 2022 at 14:03
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    My point is that the thought could belong to nothing, but I'm trying to figure out why it couldn't. Also, if the thought imagining the thinker is enough to say that the thinker (so, I) exists, then a lot more things exist just because we create them, though I'm not sure I understood your second point. Commented Dec 27, 2022 at 14:11
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    Yeah. Me either. Commented Dec 27, 2022 at 14:16
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    Because thinking is a mode (an affection) of thinking substance (mind). Commented Dec 27, 2022 at 14:24
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    It doesn't, this is a well-known gap in Descartes's argument, see Could 'cogito ergo sum' possibly be false?
    – Conifold
    Commented Dec 28, 2022 at 8:23

10 Answers 10


The "I" of the Cogito does not stand for Descartes, or for the subject, or for the subject's self. It stands for the thing thinking the Cogito when the subject thinks the Cogito.

The original Cogito, in French, "Je pense, donc je suis" translates in English not as "I think, therefore I am" as is usually offered, but as "I am thinking, therefore I am", which seems pretty incontrovertible.

That being said, the Cogito is not an argument. It is performative logic. Any human being in good mental health can think the Cogito for him or herself and experience the truth of the premise and so the truth of the conclusion.

No human could possibly convince another being, human or not, of his or her own mind's existence. The Cogito is meant for the thinker to think the obvious truth that as you are thinking, you are. It is logical but it is not an argument.

The whole point of Descartes' disquisition about doubt was to show that the idea that we possess knowledge of the world outside our mind is delusional. Given this, Descartes would obviously not have meant the Cogito as the incontrovertible proof (to other people) of his own existence.

"I think therefore I am" is egocentric because could really stem from an illusion of the thoughts belonging to an owner

Given what I just explained, it should be plain that the Cogito is not "egocentric".

Similarly, it is clear that Cogito does not say that our "thoughts" belong to "an owner". In fact, the whole point of the Cogito is that the "I", the thinking thing, does not actually know that there is a human being thinking the thoughts. It believes there is, but it doesn't know. This is expressed by Descartes' idea that we can doubt the existence of our own body. And this leaves zero room for illusion.

I don't really see why a thought couldn't exist on its own?

This possibility is not incompatible with the Cogito, but this was not Descartes' point. The "I", the thinking thing, believes it has a corporeal body. What Descartes' argument about the possibility of doubt is that it is only a belief, not actual knowledge, and as such it leaves open the possibility that said body doesn't even exist. However, Descartes is clearly not interested in going there, contrary to what many philosophers suggest with the fallacious equation "Cogito = Solipsism". Descartes doesn't want to argue solipsism because he is not solipsist. He explicitly recognises and acknowledges in his argument about doubt that we readily believe we have a corporeal body, that there is a material world outside our mind, that there are other people. His point is only that we know our own mind exists and we can only believe that our corporeal body does.

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    – Geoffrey Thomas
    Commented Jan 1, 2023 at 16:34

Who is thinking? You. So you exist.

The "I think therefore I am" is in response to question "What really exist?". The phrase response by saying that "Atleast I exist. I can be sure of that, because I just thought something. If I didn't exist I wouldn't have think that".

The thought can sure exist without you. Thats not the point. The point is, the thought cannot be thought by you if you don't exist. You would agree to that.

Edit (added): Let me prove this by contradiction. Can you think and do not exist? If so, who is thinking? The P part already take it for granted that "I think". Descartes argument is built on that. If you don't exist then you cannot do anything. How can you think then?

  • When you say the "thought can exist without you", I think you mean the contents of the thought, don't you? When I think of the thought, I mean the experience of it, not the contents, and I'm not sure how it would make any sense to say a thought exists if it's not the one that is experienced. But I didn't really think of the definition of thought to be honest and I think I'll be thinking more about what it is and defining my problem better because I'm getting lost right now. Commented Dec 27, 2022 at 14:40
  • @Gui yes, the contents of thought obviously. It would be someone else thinking. It can be any thought, thats the point. "I think therefore I am" is not specific to a particular thought. It can be thought about a chair, about a girl, about sky whatever. If I can think (about anything) I must exist (otherwise, who is thinking?)
    – Atif
    Commented Dec 27, 2022 at 14:46
  • Okay, so if I rephrase it, if we say the thought is the content and not the experience, at least we can agree that the action of thinking is the experience. And I'm pretty sure Descartes means that when he says "I think", doesn't he? He thinks he is there to experience that content whatever it is. I know it's not specific to a particular thought. Whether other people have that experience is out of the question as well. So back to mine, if we go to the essence of what the experience is, why can't it exist alone? That experience is what is percieved and that's the sole thing in the world. Commented Dec 27, 2022 at 14:55
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    The expression is "I think therefore I am". The "I think" part is pre-supposed. Its a given as far as this expression is concerned. You cannot question the P in P implies Q. All that you can do is argue that P do not imply Q. If you don't think that its you who is thinking then Descartes have nothing for you.
    – Atif
    Commented Dec 27, 2022 at 16:29
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    Your problem is you are not looking at data (observation) with a clean head. Descartes was thinking "Do anything exist?" Then it occured to him that this very thought, that happened to him, proved that atleast he exist. The "that thought that just occured to me" is data. You are arguing that he pre-supposes the "I", how can he be sure that its he who had the thought? Well, thats his observation. His data show that. He dont find anybody else having the thought. If the thought is shared there is no evidence of it so why suppose that? "All he know" is, he thought :)
    – Atif
    Commented Dec 27, 2022 at 16:37

It doesn’t imply there is a thinker. What would it even mean for there to be a thinker? You would need some already pre existing entity experiencing the process of a thought. But wouldn’t this entity be encapsulated by yet another thought? That would be circular.

If what Descartes really meant is that you can’t doubt anything except the experience in your mind, then it would have been better to simply state that as such. The “I think, therefore I am” phrase seems meaningless.

  • Thanks for your answer Commented Dec 28, 2022 at 8:50
  • I try to tell people this, but it doesn't go over well: "What would it even mean to say that you exist?" ha ha
    – Scott Rowe
    Commented Dec 28, 2022 at 11:42

Descartes presumes thinking is an action performed by someone; thus, if it is occurring, then someone must exist to be doing it. The thought can’t occur without a thinker there to think it.

The Taoist philosopher Zhuangzi (a.k.a. Chuang Tzu) suggested the possibility of mistakenly identifying the thinker: “Once upon a time, I dreamt I was a butterfly…. Now I do not know whether I was then a man dreaming I was a butterfly, or whether I am now a butterfly, dreaming I am a man.” However, whether man or butterfly, again someone was doing the dreaming — or thinking.

The Matrix films bring up another way to look at it: when Neo is still in the Matrix thinking he exists in a human city, the thought is being performed by a real human being inside a cocoon, in effect “dreaming” his alternate existence. He still exists, just not how or where he believes.

The knotty question is, when the AI program “Agent Smith” expresses opinions, in effect also saying “I think…”, does that mean he exists? Or is the actual “thinker” the Matrix itself, of which he is merely an aspect or expression? (But again a “thinker” exists somewhere, just not how or where it appears to — a case of Zhuangzi’s dreaming butterfly.)

Likewise, if you’re in a role-playing game such as D&D, and declare your character “thinks” something, does that character really exist? Or are you the actual thinker of that thought? (What if you don’t think the same thing as your character, i.e., you think your character is mistaken?)

If your computer, of whatever size, asserts the Cogito — does it thereby acquire civil rights as a sentient being? Or can you declare the Cogito false in that situation? If the latter, why not in all situations declare that others are not really thinking/existing — the solipsistic position? Then why not go further and suspect that you yourself do not really think or exist — but are only a butterfly’s dream? That the thought occurs, but does not come from you the human being, only from some other place? Perhaps we are all simulations within one great computer….

Conversely, if you sit zazen and successfully stop thinking, do you then cease to exist?

  • Ah, but if you think that your character has a mistaken thought, does that mean that mistaken thought actually exists, any more than, say, the the dragon that he mistakenly believes somewhere other than its lair?
    – Mary
    Commented Dec 30, 2022 at 0:59

So the idea you're proposing is Hume's bundle theory of self:


ie: there are just a bunch of thoughts/sensations without some entity "having" all these thoughts/experiences

Some objections:

  1. The standard objection is how are all these thoughts/sensations bound together if not by some entity. These thoughts/sensations are somehow unified together.

  2. I don't see how there can be "pain" without some being that is "in pain". Certain sensations are pleasant/unpleasant... without being pleasant or unpleasant to anyone?

EDIT: I think feelings are much more indicative of a subject. For example feeling cold. How would a "feeling" exist apart from a being having a feeling. And I think Descartes really meant for his argument to encompass all types of experience, not necessarily just "thoughts". So "I feel" therefore "I am."

  • Thanks, that seems interesting, I will read about that! Commented Dec 28, 2022 at 8:53
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    If you consider a collective entity like a forest or ant colony, the collective might have issues that the individuals do not. Each ant might have enough food for example, but the overall food supply might be dwindling. So 'bundles' can have different issues than individuals or parts. Maybe that is what is meant?
    – Scott Rowe
    Commented Dec 28, 2022 at 11:40

The most that Descartes was entitled to say was that "thinking is occurring", not that "I am thinking". That is an entirely a valid argument as stated on the wiki page of Cogito Ergo Sum.

Dubito / Cogito - Ergo Sum isn't stated to emphasize the self, I. It is a reflection on existence vs dream and immateriality ... also free will.

Descartes was interested in free will, volition and self awareness, as they weren't as formalized in the philosophy of his time.

Dubito ergo sum also emphasizes the cynicism that is necessary for higher thought and awareness of conflicting views.

  • I see, thanks for your answer! Commented Dec 28, 2022 at 8:51

To be anachronistic: imagine formulating the cogito in the flavor of modern first-order logic (not "real" FOL altgoether, though; as I'm looking over what I've written here, my mind is screaming at me that the translations I've given have the same flavor but aren't really the same dish, so to speak). Let i be the (to-be-bound) variable and T the predicate of thought. Then, in FOL, we would not merely write Ti, but ∃i(Ti). By A&BA (not in a strictly valid manner, though) we can then generate the following line of reasoning:

  1. i(Ti)
  2. i(Ti) → ∃i
  3. ∴ ∃i

A somewhat different way of saying it:

  1. x((x = i) & Ti)
  2. i → ∃x
  3. ∴ ∃x

(2) in the first reformulation of the cogito is not strictly valid, or perhaps is not strictly well-formed (regardless of validity) in that we're not FOL-wise meant to write down quantified expressions "just like that." I'm not actually sure how the equals sign works in FOL, so I'm not sure about if (1) in the second reformulation is licit. Anyway, the whole bit can be convoluted some by consideration of the theory of indexicals as a whole, since i is meant as an indexical variable.

Again, there seems to be something off about these reformulations. The SEP article on Descartes' epistemology mentions competing interpretations of the cogito as an axiom vs. as a theorem. The presence of a "therefore" in some versions of the cogito makes it look theorematic, but as the above shows, it's hard to make it look theorematic in anything more than an, "AA," kind of way.

Alternatively, I'm actually sympathetic to the idea that the cogito falls apart on a deeper level, in the sense that I'm not sure that the concept of existence is ultimately coherent, in which case "inferring" the existence of something will be an invalid inference by the by. So one would be able to say, "I think, but I don't exist; I don't anti-exist, either; indeed, nothing exists or anti-exists." Then the cogito would become, "I think; therefore I think."

Addenda. Here are some other "deviant" options, with their problems mentioned in passing:

Work in a modal logic with an actuality operator on propositions, where, "⚬A," reads, "It is actual/actually true that A." See Bumble's answer to this PhilosophySE question for what seems to be an indirect counterexample to, "A → ⚬A," but otherwise assume that A → ⚬A. Then say:

  1. Ti → ⚬Ti
  2. Alternatively, ∃i(Ti) → ⚬∃i(Ti)

Still, not really anything better than AA, it seems. —Background problem (in Descartes hermeneutics, anyway): Cartesian modal logic seems to encode for contingently necessary truths, so one would like to be careful about how one might read an actuality operator into that logic (contingently necessary truths fly in the face of standard modal logic, wherein ◊□A goes to □A; so since Cartesian modal logic is nonstandard by the by, one is reluctant to haphazardly throw an actuality operator into that mix).

Even more deviously:

Work in a logic with an existence predicate E!, like a Zalta (or pseudo-Zalta) logic for abstract objects. Then write (for any generic variable x and any generic predicate F):

  1. x(Fx) → ∃x(E!x)
  2. i(Ti)
  3. ∴ ∃i(E!i)

Background problem: again, as far as interpreting Descartes goes, one wishes to be careful about introducing existential quantifiers and predicates together, especially in the form of a conditional like (1) that seems as if it would have to be as fundamentally knowable (if knowable at all) as the cogito is itself supposed to be.

One more option, here:

Work in a weak epistemic (propositional) logic ("weak" as in "not thought out in much detail"), where, "kA," reads, "It is known that A." For present purposes, also use E! instead of ∃. Say that:

  1. k(Ti)
  2. k(Fx) → k(E!x)
  3. k(E!i)

This seems theorematic enough to license a "therefore" in its wording, though again, now, isn't (2) a principle that has to be as fundamental as the cogito is supposed to be?

A parallel interpretation problem. Another way to reformulate it could be, "I perform the act of thought; therefore, I am a substantial being." Not just, "I perform an action; therefore, I am an active being," but a substantial one, and Descartes inherited the waning of scholasticism, especially considering his ethnicity/nationality, so even so did he mean by "substance" what the scholastics attributed to Aristotle, viz. the doctrine that the things worthy to be called by the name of "substance" were those things which "are always a subject and never a predicate only" in the objective ordering of form and matter.

So this is a stronger claim than, "I think, and my thinking implies my existence." He is specifically claiming that he knows, from the fact that his thoughts are his own actions, the deeper fact that he is such as to be a "subject that can never only be predicate." In this, he is significantly prefiguring Immanuel Kant's use of what Kant calls "the" I-think, a fundamental propositional force in empirical cognition, a proposition-forming operator that is constantly taking operands and yielding much of our cognition thereby. Recall that Descartes at one point (not necessarily in the Meditations, or I mean I don't recall where exactly) goes over the difference between adventitious ideas and innate ideas. This inner capacity to differentiate ideas both formally and materially establishes that these ideas are predicates of us by the by, are predicates of the I-think even, whereas the I-think can become its own predicate, as I-think-that-I-think, but only then in such a way that it remains a subject of itself. So it satisfies the postscholastic sense Descartes had about the concept of subsistence (not necessarily the wording he used, granted, but more like his culturally conditioned propensity to use the kinds of concepts that are affiliated with the word often enough, and especially in philosophy).

Accordingly, "I think," would go to, "I perform the act of thought, which means that I am a substance of which thoughts are predicates."

One last reformulation, in erotetic logic. Usually, erotetic logic is understood as the art of inferring questions from assertions, or from other questions. Inferring assertions from questions is not often explicitly spoken of, though G. E. Moore's open-question argument might be styled such an act of reasoning. Alternatively, tracking the alleged presuppositions of a question could be thought of as transcendentally arguing from questions to assertions. So now consider:

  1. Do I exist?
  2. ∴ I do exist.

This will perhaps not be a universally valid argument scheme, i.e., "Does x exist?" will not always go to, "x does exist." At least, we might rephrase the inference so:

  1. Is there an x such that I am x and x is asking this very question?
  2. ∴ There is an x such that I am x and x is asking this very question.

Then the inference to me as existing is given through the indexical for "this very question," i.e. that impersonal indexical nevertheless is convertible into the personal one, "and we are done." QED

  • I'm not sure I completely understood your answer, but I think what I'm questionning is ∃x. Is the "there exist something that this thought is from", or said an other way "something has to be the source of the thought" just accepted or is there an explaination? Commented Dec 27, 2022 at 14:23
  • @GuillaumeDerex, there's the rub. Descartes can't really get the cogito off the ground as a theorem, as a statement worthy of a "therefore," without assuming the thing to be proved. Yet for all that, he didn't always write down the cogito with a "therefore" in place. Alternatively, we have a case where coherentism is in play, with all the attendant advantages and potential drawbacks. Commented Dec 27, 2022 at 14:31
  • thanks for your answer, it makes more sense to me now. Commented Dec 27, 2022 at 14:42
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    This line of reasoning doesn't get you to an 'I' but to a subject that is thinking. Nor is the thinking thing guaranteed to be unique. This may mirror the traditional criticism of Descartes' argument that he is not entitled to claim "I am thinking" since this presupposes a single coherent and persistent self. If you start instead from "there are some thoughts" then it is difficult to make progress without additional assumptions.
    – Bumble
    Commented Dec 27, 2022 at 19:25
  • @Bumble, yeah the i-variable has to be presupposed as an indexical, and a specific kind of indexical then. I think SpeakPigeon's observation about how the cogito reads in the French original testifies on behalf of an axiomhood vs. a theoremhood picture of the cogito. Then perhaps the "therefore" in other text might be better taken for a conditional arrow more than a three-dots triangle counterpart. Commented Dec 27, 2022 at 22:37

Descartes believed that the fact that he was able to think, and that he was aware of his own thoughts, proved that he existed as a thinking being. He argued that the only thing he could be certain of was his own existence as a thinking being, and that everything else was open to doubt.

This idea is known as Cartesian dualism, which is the belief that the mind and the body are separate entities. Descartes believed that the mind, or consciousness, was the non-physical aspect of a person, while the body was the physical aspect.

So, in the phrase "I think, therefore I am," the act of thinking is used as evidence of the existence of the thinker. Descartes believed that this was the only thing that he could be certain of, and that everything else was open to doubt.


In relation to your statement:

"I don't really see why a thought couldn't exist on its own".

As linked by Conifold in the comments, a hugely popular and accepted answer to 'Could cogito ergo sum possibly be false?, states:

Possibly, "there are thoughts" is the true minimum statement that can be reached using Descartes' method; this does not presuppose the existence of some sort of unified consciousness having the thoughts.

This leads to contemplation of how thoughts might exist in the absence of a thinker.

Four ways in which thoughts might exist without a thinker (which likely point to there being others as well):

  1. Thoughts might exist post-death of the thinker, much like smoke might exist after the extinguishing of a fire. This may align with aspects of mind-body dualism.
  2. A sufficiently advanced species might program thoughts into some kind of ether or application, where they reside as phenomena providing the illusion of having been thought when in fact they were merely constructed. See simulation hypothesis.
  3. If infinite universes exist, thoughts might inevitably come into being, as emergent phenomena not of a thinker, but of sheer randomness.
  4. If it eventuates that there is in fact some kind of mental realm beyond the physical, as some people seem to believe (again, see mind-body dualism, then the thoughts of different people could feasibly coalesce into new thought forms, like water from a river entering a sea.

I'm not a philosopher but an engineer, so I try to argue purely logical, without interpretation of what a thinker or a thought is.

For me your premise is invalid.

"How does a thought imply there is a thinker in "I think therefore I am"?"

"I think therefore I am"

Where in that, do you read, that there is a though?

"to think" is a verb here, a process, an action being performed.

"I" is the subject performing that task.

My premise is: There is no statement or implication whatsoever, that an object of type thought is required for the subject to perform the action. The execution of said action is actually proofing the subject existence. At least that is the logical statement here (independent if its truth value). There is no thought at all, unless you interpret, hat said action requires one - which is not stated. Maybe the thinker "thinks a dream or a fart".

Surely, as you say, a thought may exist without any attachments, but that is unrelated (without further conditioning or interpretation) to the (English) phrase in question.

I read somewhere:

On stackoverflow invalidating a premise is also a valid answer

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