Descartes famously argued that the one undoubtable truth is that when he is thinking he exists. This idea, I think therefore I am, is clear and distinct, which are the marks of self-evident necessary truths. Descartes’ idea still has a lot of pull, but isn’t there an obvious kind of counter-example to it?
Couldn’t it be the case that the Evil Demon has multiple personality disorder and that I (or you) am a figment of this fragmented consciousness? Couldn’t it be the case that the Evil Demon has made me up in the telling of some story to ease his boredom? Or maybe the Evil Demon is a Solipsist. In reality He is the only thing that exists and all of us are just a backdrop his all-powerful mind has concocted…It would then be the case that I wonder whether I exist and yet I do not exist…aren’t these kinds of things counter-examples to the Cogito?
One response that might be made is that, while it is the case that I do not technically exist as I thought I did (as a mind-independent entity), I still exist (as a fictional mind-dependant entity). So, I still exist, just not in the way that I thought I did. This would allow us to keep the general truth that whenever there is some thinking there has to be a thinker (it would just be the Evil Demon himself who is actually doing the thinking), but it does seem to do violence to clearness and distinctness as a criterion of self-evident necessary truths.
Does anyone know if this kind of objection is ever dealt with by Descartes or any of his objectors/commentators?
Richard Brown 
Giambattista Vico argued, I forget on precisely what grounds, that the most Descartes could get is “I think, therefore something exists”, which is at least along those general lines.
Hi Brandon,
Thanks for the tip!
I don’t know much about Vico except that he was a poet who did not like Descartes’ philosophy and looks like an early constructivist…but you reminded me of Kant’s argument against Descartes. Kant argues that the Cartesians are mistaken in thinking that they can tell the true nature of the mind from introspection. We cannot tell if the mind is physical or non-physical. All we can conclude is that there is a noumenal self whose nature, like all noumena, must remain mysterious to us…this is just further evidence for the importance of Kant…but I think it also shows something else that Kant would not agree with. It shows that the true nature of my noumenal self may turn out to be not myself. If I am a figment of the Demon’s mind then there is not a distinct noumenla self that corresponds to my thinking. There can be self consciousness without a noumenal self…
Hi Richard,
I’ve often wondered why Russell thought that the Cogito should’ve been “I think, therefore there is thinking.” He didn’t give any reason that I’ve read about; but as a fan of Descartes, I totally love your hypothesis “that the Evil Demon has multiple personality disorder and that I (or you) am a figment of this fragmented consciousness”. There seem to be only two possible conclusions:
Yours)… I might be a fictional mind-dependent entity
Mine)… I might be a mad Demon
I regard it as obvious that no actual entity such as (by definition) myself could be fictional (except analogically, as when we think of the Creator as our author), even if fictional entities can be said to exist (in some sense), whence I prefer the second conclusion. Basically my response is sure, I might be wrong about much of what I think I know about myself.
It’s an interesting question, what I could not possibly be wrong about. In view of my conclusion, I think that I remain totally justified a priori, in my certainty that I exist; although that does depend upon my own interpretation of “I” as referring, not to some socially-defined personality (as some materialists would have it), but to some essential subject (so maybe I’m assuming that I exist in order to get my conclusion?)
Seems that what is lurking behind your response is a metaphysical commitment to the existence (in what sense?) of fictional objects. Just as ‘Santa Claus’ or ‘Sherlock Holmes’ would be analog concepts (not ‘unicorn’, at least if you by Kripke’s notion that ‘non-existence’ is a necessary property of a ‘unicorn’. Seems to be a form of fictionalism.
Hi Enigman, thanks for the comment!
Yeah, I think I agree that your option is an option (I sort of leaned this way already in the above comment to Brandon). Of course if you turn out to be the evil demon then that doublly skewers Descartes argument for the existence of God. Since it cannot be ruled out a priori that you are not really the evil demon you very well might have been the source of your idea of an infinite being. So, I think that Russell is right abou this. all we can get is that something thinks. We don’t get that enigman thinks, for it may be the evil demon that is doing the thinking!
Hi Flaffer, thanks for the comment as well!!
Sorry, but that link is messed up…but yeah, I guess I was assuming a commitment to fictional entities along the lines of Kripke’s view
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