After a discussion about the "difficulties to distinguish knowledge from faith" someone replied to me that the quote implies faith because it uses the word "think". But as it is generally understood:

As Descartes explained, "We cannot doubt of our existence while we doubt." A fuller form, dubito, ergo cogito, ergo sum ("I doubt, therefore I think, therefore I am”), aptly captures Descartes’ intent.

The quote is used by Descartes so to define secure knowledge.

by wiki:

This proposition became a fundamental element of Western philosophy, as it purported to form a secure foundation for knowledge in the face of radical doubt.

This "I am means i securely know that i exist.


In Principles of Philosophy Descartes's notes:

Latin: "Non posse à nobis dubitari, quin existamus dum dubitamus: at que hoc esse primum quod ordine philosophando cognoscimus."

English: "That we cannot doubt of our existence while we doubt, and that this is the first knowledge we acquire when we philosophize in order."

The proposition is sometimes given as dubito, ergo cogito, ergo sum. This fuller form was penned by the eloquent French literary critic, Antoine Léonard Thomas, in an award-winning 1765 essay in praise of Descartes, where it appeared as "Puisque je doute, je pense; puisque je pense, j'existe." In English, this is "Since I doubt, I think; since I think I exist"; with rearrangement and compaction, "I doubt, therefore I think, therefore I am", or in Latin, "dubito, ergo cogito, ergo sum".

A further expansion, dubito, ergo cogito, ergo sum—res cogitans ("…—a thinking thing") extends the cogito with Descartes's statement in the subsequent Meditation, "I am a thinking (conscious) thing, that is, a being who doubts, affirms, denies, knows a few objects, and is ignorant of many …". This has been referred to as "the expanded cogito".

So the question is what is the consensus about this argument regarding secure knowledge? As i know all major philosophical doctrines espouse it (including idealism of all forms, materialism) and only radical skepticism and poor empiricism tries to attack it.

  • 'Dubito ergo sum' goes back to Augustine, and is the indirect motivation for 'cogito ergo sum'.
    – user9166
    Commented Oct 25, 2015 at 17:14
  • This question has been answered before philosophy.stackexchange.com/questions/70/… The consensus is that Descartes's argument doesn't work, one does not have to be a skeptic for that. The most obvious leap is from doubting and thinking to "I think", where "I" is an item smuggled in from an insecure empirical observation that thinking is usually accompanied by a thinker. But cogito does not even establish that doubting and thinking "exist" securely, if thinking was enough to produce knowing we could know that unicorns exist by reflecting on them.
    – Conifold
    Commented Oct 26, 2015 at 19:19
  • Psychoanalysing people is still not what we are here for. Finding a philosophical weakness in an argument is not the same as directly believing its opposite. And it says nothing about the psychology of the philosopher.
    – user9166
    Commented Oct 26, 2015 at 19:51
  • @John Am I am not even expressing my own view, the objection is so well known that even Wikipedia lists it, along with many others en.wikipedia.org/wiki/… Descartes also made many other well known logical mistakes in his reasoning, for which he can be easily forgiven considering he was one of the first to advance a completely new style of philosophy. His mistakes seem silly only in hindsight, after they were analyzed to death by countless people. Today, the insecurity is in needing "affirmation" of self-existence, and settling for cogito.
    – Conifold
    Commented Oct 27, 2015 at 1:12
  • @ Conifold My argument was not pointed to you personally but to the way of thinking that rejects ability of a self to affirm own self. For me needing "affirmation" for self existence is not right. Who gives this affirmation?
    – John Am
    Commented Oct 27, 2015 at 9:08

4 Answers 4


According to Descartes, his methodological doubt does not confirm his existence as a person with mind and body.

Descartes divides the human being into two components, body (res extensa) and soul = mind (res cogitans). Hence any mental activity, notably doubting or reasoning, demonstrates the existence of mind. But it does not prove that the ideas of his thinking have a relation to reality, i.e. that the ideas refer to existent objects. Hence thinking alone does not prove the existence of the second component, the body.

But Descartes develops an argument how one can conclude that also the body exists. This argument employs the idea of God. It is expanded e.g., in Descartes's Meditation.

For the whole issue see also How does Descartes use god in his Meditations? and Besides the Cartesian Circle, what flaws are there in Descartes' use of God .

  • 1
    Yes, it is secure knowledge - according to Descartes. Namely clear and distinct insight. But the fact, that clear and distinct insight affirmes the thruth of the insight, does not follow as a direct consequence from the mental activity of doubting. It follows by the whole argumentation expanded in the Meditations - according to Descartes.
    – Jo Wehler
    Commented Oct 25, 2015 at 9:22
  • 3
    @draks According to Descartes there is a gap between body and mind. The methodoligal doubt affirmes only the existence of the mind. The conclusion from the existence of the mind to the existence of the body is achieved by a long argumentation in the Meditations.
    – Jo Wehler
    Commented Oct 26, 2015 at 12:30
  • 1
    and the long way is necessary, since we can't be sure if there is a demon sitting in front of the mind, making us believe that we sense things and (re-)act on an outer world. Like that?
    – draks ...
    Commented Oct 26, 2015 at 12:37
  • 2
    @draks: Yes :-)
    – Jo Wehler
    Commented Oct 26, 2015 at 14:16
  • 1
    since you agreed, you also agreed that there is an interface from the mind to something outside the mind, right? How else would the putative evil genuis be able to draw a red herring across our track?
    – draks ...
    Commented Oct 27, 2015 at 7:11

See Descartes' Epistemology : 4. Cogito Ergo Sum, for some key points, including :

In short, the success of the cogito does not presuppose Descartes' mind-body dualism.

[...] much of the debate over whether the cogito involves inference, or is instead a simple intuition (roughly, self-evident), is preempted by two observations. [...] As Descartes writes:

When someone says “I am thinking, therefore I am, or I exist,” he does not deduce existence from thought by means of a syllogism, but recognizes it as something self-evident by a simple intuition of the mind. (Replies 2, AT 7:140).

  • Thanks for your insight. I have to reread the replies it is an important part of the meditations. Yes "cogito", is not a syllogism is a compact form -a resume- of the elaborated confrontation by Descartes of the problem of knowledge. So (according to Descartes) this self-evident thing is a truth, a secure knowledge about ones mind existence or not?
    – John Am
    Commented Oct 25, 2015 at 11:31
  • en.wikipedia.org/wiki/Archimedean_point
    – John Am
    Commented Oct 25, 2015 at 11:51
  • @JohnAm : according to my understanfing, intuition for D is a "source" of certain knowledge, like the intuition of the basic facts of geometry and mathematics. Thus, the intuition inherent to the cogito is the certainty that the "perception" of my act of doubting is inscindible from the "perception" of my mind (my I) performing that act : je pense, donc je suis. Commented Oct 25, 2015 at 12:03

Your question was, What is the consensus about this argument..?

As Conifold noted, it is not generally accepted today... as an argument. This is not a malign judgment about whether or not things exist. Or even whether "secure" knowledge exists. It is simply that his argument, as observed by Jo Wehler does not really have the sort of empirical component modernity expects and ends up based on intuition, God, and some circularity.

And as Conifold said, it infers an "I" from thinking. Again, this is not a question of solipsism or radical skepticism. It is just that an ""I" has a lot of implications in it. Some might assume it entails a body. Or a certain type of continuity that stands apart from the body. Or a psychological ego with needs of of some sort. So the complaint is that this "secure foundation" is more like a rabbit out of a hat. A more judicious wording might go, "There is doubting, so there is some doubting substance."

In a sense, Descartes was more or less "clearing the decks," and employing radical doubt to refute it. But you are mistaken to assume all the "great thinkers" simply accepted this particular argument. That is not the case for either Kant or Hume, for example, nor for most modern philosophers. What was crucial was Descartes' whole approach.

To say that the "consensus" do not find it inarguably "secure" does not mean a wild leap into nihilism and epistemological anarchy. Indeed, many find Descartes too close to solipsism for comfort. He begins with a cellular autonomy that does not really account for other minds and requires great mental labors and a deity to arrive back at "things."

  • Thanks for the answer. It seems to me that in relation to some "modern" trends in epistemology Descartes position "close to solipsism" and the "great mental labors and a deity to arrive back at things" are worth the effort because at the end you get minds, things and even a deity. I admire skepticism as a knowledge tool, but careless usage is like putting your finger down the drill.
    – John Am
    Commented Oct 26, 2015 at 23:43
  • Kant thought that skepticism was entirely necessary, but most necessary in defending against skepticism itself. You cannot win against the skeptic, but you can always fight skepticism to a draw and turn to other matters. Skepticism itself is not a belief system. So most "skeptics" are simply posting warnings against hasty acceptance of certain "truths" or ways of reasoning. In Hume's Scotland, for example, people could still be hung for refuting the "truths" of the church. His attack on "truth" was a humane endeavor. Commented Oct 27, 2015 at 1:01
  • I started the whole thread as a reaction to repetitive statements driven by "modern empiricism" that refute knowledge of one's self but affirm a god with easiness. I will continue to attack this type of humanitarian obsolescence.
    – John Am
    Commented Oct 27, 2015 at 8:25
  • Hmm. I don't know which philosophies you refer to. But "self" and "God" are not stable, obvious terms of reference, so much of the argument may hinge on those concepts and their meanings. And culture comes into it. Some of the critical attacks on the "self" and defense of "God" may be acting as correctives to a modern society with an unexamined and unbalanced emphasis on the "individual," utilitarianism, and consumerism. Commented Oct 27, 2015 at 12:39

Is it: Some 'thing' 'thinks' (or produces what we call thought) and therefore some 'thing' is? Wow, that solves everything!

Nietzsche Beyond Good and Evil: Let the people suppose that knowledge means knowing things entirely; the philosopher must say to himself: "When I analyze the process that is expressed in this sentence, 'I think,' I find a whole series of daring assertions that would be difficult, perhaps impossible, to prove—for example, that it is I who think, that there must necessarily be something that thinks, that thinking is an activity and operation on the part of a being who is thought of as a cause, that there is an 'ego,' and, finally, that it is already determined what is to be designated by thinking—that I know what thinking is.

With regard to the superstitions of logicians, I shall never tire of emphasizing a small terse fact, which these superstitious minds hate to concede—namely, that a thought comes when "it" wishes, and not when "I" wish, so that it is a falsification of the facts of the case to say that the subject "I" is the condition of the predicate "think." It thinks: but that this "it" is precisely the famous old "ego" is, to put it mildly, only a supposition, an assertion, and assuredly not an "immediate certainty." After all, one has even gone too far with this "it thinks"—even the "it" contains an interpretation of the process, and does not belong to the process itself. One infers here according to the grammatical habit "thinking is an activity; every activity requires an agent; consequently—."

  • If you have references to those who take a similar view this would help support your answer and give the reader a place to go for more information. Welcome. Commented Oct 10, 2019 at 13:07

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .