"cogito ergo sum" and then...?



After his ever so famous "cogito ergo sum", Rene Descartes' second (deep?) thought was something like "God exists" (according to my literature). I think he brought this up mainly due to historical reasons or personal belief, but to me (although I believe in something) that's far less obvious than how he started out.

Why didn't he at least continue with something like "there exist impressions, that fed my mind, such that I can doubt their existence, because I think they are created by putative evil demons" or "there exist senses, that fed my mind with data, be it right or wrong"?

To me, these two expressions are as clear as the first one. Am I right and are there other simple truths?

draks ...

Posted 2014-03-24T21:59:53.843

Reputation: 708


Not at all. That conclusion is based on his ontological arguments, not cogito. Re-read the Meditations (Meditation 5 in particular). This SEP article should help.

– Hunan Rostomyan – 2014-03-24T22:12:29.160

Not at all what? You mean the conclusion that God exists is not based on cogito? I agree on that. But what about "there exist senses that fed my mind"? – draks ... – 2014-03-24T22:27:46.427

The 'continuation' you're offering is something he began with, namely that sense impressions cannot be trusted (given the possibility of the evil demon). Cogito is something that follows that thought. – Hunan Rostomyan – 2014-03-24T22:36:01.320

@HunanRostomyan ok, but this fact that doesn't matter to my question. Thanks for the link... – draks ... – 2014-03-24T22:38:02.477

1Well, in that case: what is your question? – Hunan Rostomyan – 2014-03-24T22:39:25.380

@HunanRostomyan if "there exist impressions that fed my mind such that I can doubt their existence" or "there exist senses that fed my mind" would be as valid/true as "cogito ergo sum"? – draks ... – 2014-03-24T22:41:49.307

I'm having trouble parsing your first two sentences. Perhaps someone else will understand what they mean. I give up. – Hunan Rostomyan – 2014-03-24T22:46:36.533

@HunanRostomyan too sad. One last shot: Rene says something like "I doubt my sensation, therefore I am". Why doesn't he say "There is sensation"? Without judging if it's true or false. – draks ... – 2014-03-24T22:53:30.090

1That there is a sensation is indubitable, actually. While the existence of the sensation is indubitable, the possibility of the evil demon makes it impossible to say whether the sensation has the appropriate kind of causal relations to the world. Concretely, if you look at object x and see it to be a red apple, it is indubitable that you're experiencing redness!, but it is dubitable whether x is actually a red apple (because it's possible that the evil demon is intercepting the light emanating from a green apple and messing with the frequencies before it gets to you). – Hunan Rostomyan – 2014-03-24T23:31:41.427

It is not clear to me if you are concerned with (i) an "emeneuthical" issue , i.e. the "correct" reading of Descartes' work and thought, or with (ii) a philosophical "review" of the soundness of Descartes' argument. About (ii), it is clear that he do not achieve "indubitable" foundations regarding human knowledge ... we are still discussing about it today. – Mauro ALLEGRANZA – 2014-03-25T07:36:19.550

@MauroALLEGRANZA I'm concerned about (ii)...What do you think of my extensions? – draks ... – 2014-03-25T08:13:48.373

@HunanRostomyan I would be glad to read your opinion on Mauro's answer? – draks ... – 2014-03-26T11:22:19.783

@draks... Sorry for the late reply. I more or less agree with him. – Hunan Rostomyan – 2014-03-27T18:39:17.473



The path Descartes followed from the "discovery" of the "first truth" : cogito, ergo sum to the existence of the self, God and the external world was a complex one, made of all the six Meditations, with a lot of subtle arguments :

The cogito raises numerous philosophical questions and has generated an enormous literature.

You must follow this path at least trough the relevant SEP entries : Descartes' Ontological Argument and Descartes' Epistemology :

Descartes' reference to an “I”, in the “I think”, is not intended to presuppose the existence of a substantial self. In the very next sentence following the initial statement of the cogito, the meditator says: “But I do not yet have a sufficient understanding of what this ‘I’ is, that now necessarily exists” (Med. 2, AT 7:25). The cogito purports to yield certainty that I exist insofar as I am a thinking thing, whatever that turns out to be.

In the final analysis, Descartes thinks he shows that the occurrence of thought depends (ontologically) on the existence of a substantial self — to wit, on the existence of an infinite substance, namely God (cf. Med. 3, AT 7:48ff). But Descartes denies that an acceptance of these ontological matters is epistemically prior to the cogito: [...].

If the cogito does not presuppose a substantial self, what then is the epistemic basis for injecting the “I” into the “I think”? Some critics have complained that, in referring to the “I”, Descartes begs the question by presupposing what he means to establish in the “I exist.” Among the critics, Bertrand Russell objects that “the word ‘I’ is really illegitimate”; that Descartes should have, instead, stated “his ultimate premiss in the form ‘there are thoughts’.” Russell adds that “the word ‘I’ is grammatically convenient, but does not describe a datum.” Accordingly, “there is pain” and “I am in pain” have different contents, and Descartes is entitled only to the former.

But note that :

As the canonical formulation has it, I think therefore I am. (Latin: cogito ergo sum; French: je pense, donc je suis.) This formulation does not expressly arise in the Meditations.


Posted 2014-03-24T21:59:53.843

Reputation: 33 575

Coming back to "senses", the thinking sense, called brain, could work without an external world (for a while, before turning insane)... – draks ... – 2018-09-24T12:56:40.173

Thank you, that was really quite interesting to read. I added the german translation. What about my question, concerning my own thoughts? – draks ... – 2014-03-25T22:00:09.663

@draks... - the german translation was not included because the paragraph is extracted from teh SEP entry and it includes only the latin and the french versions (I think because they are extracted form Descrates' later work Principia Philosophiae (1644), published in Latin and translated into French (1647). – Mauro ALLEGRANZA – 2014-03-26T08:25:46.140

I think that, basically, the aim od D was not to prove that "I" exists (and I feel, perceive, and so on ...). This is the "easy task". He want to prove that the "external" world exists: that what I feel and perceive is not an illusion but the effect of somthing independent from myself that act on me and that my "perception" of this external reality is (at least in part) "reliable". In order to achieve this goal, he needs the existence of a (non-deceiving) God. – Mauro ALLEGRANZA – 2014-03-26T09:50:35.373

If you mind, please remove the german translation. So you say that my own thoughts are kind of trivial? But still they are true, right? – draks ... – 2014-03-26T11:22:38.593

@draks... - I'm not saying that. From the fact that I think and I feel, what I can infer ? According to D, I'm not licensed to infer directly that there is something real outside me that act on my sense and that my sensations are faithful witnesses of that "something". Only through the certainty (or belief) in the existence of a non-deceiving God, I can assert this conclusion. – Mauro ALLEGRANZA – 2014-03-26T11:52:01.197

The thing is that I don't care about the external world, outside my mind. I only care about the existence of the interface to whatever. I also don't care if it is faithful. Or do you mean that we can't speak about this interface without proving that there is an real interface partner and not a evil genius? – draks ... – 2016-01-25T06:34:43.213