We recently studied about Descartes in school and my teacher said that Descartes was a sceptic, he doubted everything and had an idea of creator who decieves us. But the only thing he didn't doubt was his doubting. And we all know the famous quote by Descartes - "I doubt, therefore I think, therefore I exist".

My question/the thing I can not grasp or explain to myself is: How was Descartes sure that his doubting was his own? If this so called creator decieves us then he could as well make us doubt things just for fun? Example for this are video games now days, many characters in them are doubting but they are programmed to do so, what if we are programmed to do the same but by higher being?

Sorry if the question is lame, but I can't explain or understand this. Thank you all in advance.

  • what bearing does the origin of a thought have on its veracity? suppose the thought was one plus one equal two. Does it matter one way or the other if it was planted in one's head by someone else?
    – nir
    Commented Jun 13, 2016 at 12:35
  • 1
    This is exactly the question of the third meditation in his Meditationes de prima philosophia. If God was a deceiver, he would lack morality (broadly spoken), and in lacking something, he would not be God, i.e. perfect.
    – Philip Klöcking
    Commented Jun 13, 2016 at 12:48
  • @PédeLeão: Exactly. It is immediatly apparent through the natural light, as Descartes puts it all to often. One might argue against the argumental status of "natural light", though.
    – Philip Klöcking
    Commented Jun 13, 2016 at 12:59
  • 1
    Descartes was not a skeptic. Commented Jun 13, 2016 at 13:59
  • 1
    Of course, we can disagree with D's approach; the fact that after 400 years students are still struggling with it means that it is not so easy (as D thinked) to find an "absolute ground" for our knowledge. The best thing is to read D's original work supplemented by some good book, like The Cambridge Companion to D. Commented Jun 13, 2016 at 14:57

4 Answers 4


I don't believe that Descartes answered this particular question, but if I had to answer for him I might argue the following:

  1. Doubting by definition is experiencing.
  2. Whoever doubts is experiencing something.
  3. Let's assume that Descartes is doubting according to God's decree.
  4. Let's also assume that the doubt belongs to someone else.
  5. Since Descartes is doubting, he is experiencing something.
  6. In this case, he is experiencing something that belongs to someone else.
  7. If Descartes is experiencing something belonging to another, he is experiencing.
  8. He experienced, therefore he was.

That's a roundabout way of saying that neither the cause of the doubt nor its belonging to someone else (whatever that might mean) is relevant, given that you are assuming that he is experiencing doubt. As you said, "But the only thing he didn't doubt was his doubting."


Philip Klöcking suggested that this question might be addressed according to the fact that Descartes rejected the idea that God is a deceiver:

"From this it is manifest that [God] cannot be a deceiver, since the light of nature teaches us that fraud and deception necessarily proceed from some defect." (First Meditation)

However, that doesn't rule out the possibility of deception coming from another source, which was an idea that Descartes also entertained:

"I shall remain obstinately attached to this idea, and if by this means it is not in my power to arrive at the knowledge of any truth, I may at least do what is in my power [i.e. suspend my judgment], and with firm purpose avoid giving credence to any false thing, or being imposed upon by this arch deceiver, however powerful and deceptive he may be." (First Meditation)

In either case, he would be doubting.

  • Regarding Descartes own argumentation, see my comment on the question.
    – Philip Klöcking
    Commented Jun 13, 2016 at 12:49
  • In response to proposition 7, I think that one of the earliest parts of his Meditations discusses the inability to experience something belonging to another. This is the foundation for doubting others exist, and pushing the scope to be reduced to one's own experiences alone. Commented Jun 14, 2016 at 5:24

An uneducated opinion, but:

Because other than the game character, he (Descartes) could be presented with arguments that would remedy his doubts. And, in not accepting these arguments, he would know he's still doubting.

Or, if he does accept the arguments, he may still doubt that the arguments themselves are sufficiently thorough to accept the given context as a general truth.

PS: The video game character parrots doubts, it does not think/contemplate them.


First of all, why do you assume that the video game character's doubt does not belong to them? Yes, the creator gave them doubt but that doubt is a characteristic of that specific character and no other. The characters also exist - within the game - and so the only missing part of Descartes' statement is the "I think"

This may answer the question of how Descartes knew his doubt was his own. Descartes couldn't know that the doubt originated in himself; however, he could know that the doubt existed as a characteristic of himself. He experienced the doubt as a thought, and therefore he was.


The deceiver is primarily a concern because Descartes acknowledges that his senses are prone to defect. So when Descartes argues that his doubting is evidence of his own self, it is more a reflection that only "the fact that thought exists" confirms existence. This is how we derive "I think, therefore I am".

It is not really important whether the doubt is a programmed characteristic or not. Its that doubt inherently implies an internal consideration that is beyond that of the senses and the external world.

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