Thursday, December 16, 2010

Cogito dialogue

A short dialogue on the Cogito: inference or performance?

MARY: ‘Cogito ergo sum’ – I think therefore I am – Descartes’ famous proof that he exists!
JOHN: I don’t see that Descartes has proved anything.
MARY: Why not?
JOHN: Well, before Descartes arrives at his ‘proof’, he sets about trying to subject all his beliefs to doubt, right?
MARY: Yes. That’s his famous ‘method of doubt’. He decides to set aside all of those beliefs which he can doubt, to see if he find any indubitable certainties. He wants to identify which of his beliefs are utterly secure, so that he can then rebuild knowledge upon them. They will provide him with a firm foundation. And the cogito is his starting point – Descartes cannot doubt that he exists because, by doubting he exists, he proves that he does. It’s a self-defeating doubt.
JOHN: Hmm. I am not so sure. Look, Descartes supposes at one point that there might be an evil demon intent on deceiving him – correct?
MARY: Yes. Descartes doesn't actually believe there is such a demon, of course. But he supposes, for the sake of argument, that there might be. A demon so powerful that it could cause Descartes to have deceptive experiences, deluding Descartes into supposing he inhabits a real, physical world of trees and houses and other people, when in truth it is all an illusion.
JOHN: Right. Descartes ask himself: how can I know that I am not being deceived by such a demon? After all, everything would seem just the same. And if I can’t tell that I am not, then I cannot know that I am not.
JOHN: Right.
MARY: But then Descartes realizes that, while such a powerful and deceitful demon might deceive him about there being a physical world, it could not deceive him into thinking he exists when he doesn’t. Not even such a demon could deceive Descartes about that.
JOHN: So you say. But look, Descartes admits that such a demon might mess with Descartes’ mind in other ways too. For example, it could make Descartes go wrong in his reasoning.
MARY: Yes, that’s true.
JOHN: But then Descartes ‘proof’ must be useless. Notice the word ‘ergo’ – therefore. Descartes has constructed a piece of reasoning, from the premise that he thinks to the conclusion that he exists. Correct?
MARY: It looks that way, yes.
JOHN: But then how does Descartes know that this little argument – I think, therefore, I am – is sound? Perhaps the demon is deluding Descartes into thinking it’s sound, when it not. You see? Descartes’ proof is a piece of reasoning, and Descartes cannot yet trust any of his reasoning, because the demon might be making him go wrong.
MARY: Okay, I see the problem. Or rather I see what you think the problem is for Descartes. In fact, I think you have misunderstood him.
JOHN: How?
MARY: ‘Cogito ergo sum’ looks like an argument, a piece of reasoning, true. But it’s not. It is something else. It is a performance.
JOHN: A performance? In what sense.
MARY: By doing some thinking – some doubting – Descartes shows that he exists. He doesn’t infer he exists. He actually demonstrates it, by thinking.
JOHN: So the cogito isn’t an argument after all? An inference from the premise ‘I think’ to the conclusion ‘I am’?
MARY: Correct. If it were, then Descartes could not be sure an evil demon had not made his reasoning go wrong. But the cogito is actually a performance. Descartes proves he exists by engaging in an activity – by thinking, demonstrates he exists.
JOHN: But wouldn’t another activity do just as well? Riding a bike, say? Wouldn’t that demonstrate he exists?
MARY: No, because Descartes couldn’t be sure he really was riding a bike. The evil demon might delude Descartes into thinking he’s riding a bike, when he’s not. But the demon cannot make Descartes think he’s thinking when he’s not.
JOHN: Hmm. I am still not sure Descartes has proved beyond all possible doubt that he exists. Let me think about it some more…

7 comments:

Christopher Gray said...

What happens to Descartes when he's asleep? Does he stop 'existing' simply because his own point of view - and ability to experience his own performance - stop existing? This inconsistency is what has always bothered me about Descartes' argument.

What you've written is undoubtedly what Descartes meant, I think, but I think it reveals that he didn't - and we still don't - really have a good definition of what 'thinking' is, and why it seems indicative of something 'existing', if only from its own internal point of view.

There's another problem as well. It's almost possible today to imagine a simulation, run by this devil, that contains intelligent self-aware 'thinking' software agents. In which case, even their ability to perform 'thinking' (and their awareness of it) is still just a part of the simulation. Then the term 'existence' is really just a label saying that the simulation contains it as an identifiable entity. It's a behaviour of that piece of code, and so it can't be used to show whether that piece of code is in the simulation or in some other higher-level 'real world' in which the simulation is being executed by our devil.

According to lots of modern theorists (E.g. Seth Lloyd) our physical world can be thought of as a large 'computed' universe - a kind of simulation, but with no need for a devil to run it. Our atoms/DNA/neurons can all be thought of as information undergoing complex functions and processes, but that doesn't mean we don't 'exist'.

I think this whole argument turns on what, exactly, we think this devil would be fooling - what does it mean for us to be 'fooled', as it bears on questions of experience and existence?

The Atheist Missionary said...

I think the Cogito falls apart with the "I". What does Descartes rely on to conclude that he has an individual consciousness? Alternatively, how can he with honest skepticism dispense with the Buddhist notion of anattā (i.e. "not-self")?

Mike said...

Interesting. I don't think Mary makes a good case, though. She says Descartes doesn't infer his existence, but instead "He actually demonstrates it, by thinking." But how would any sort of demonstration have meaning unless it were verifiable--either through the senses, or by reason? Both of those, as John points out, could fall under the spell of a demon.

(One small editing point: In John's fourth and fifth statements, you have him in dialogue with himself.)

John said...

I'm not sure either that the demonstration shows there is an 'I' thinking, merely that there are thoughts. Even if we accept something is percieving those thoughts, that something may not constitute an 'I'. My thoughts about this are fuzzy, but I suppose are informed by various contemporary models of consciousness (Marvin Minsky, Daniel Dennet).

Christopher Gray said...

I agree. The information contained within a demonstration is only extractable by interpretation, and interpretation is subject to the same mischievous undermining as the processes of all reason.

If you are the only one able to experience and interpret a demonstration - from within your own perception - then what is there to distinguish that experience from the demon's injection of a similar-looking scenario into your perception?

I think there can be no escape from within the scope of subjectivity to the outer world of 'genuine' existence, simply because if there were, then that outer world would also then fall under suspicion as being contained in a further shell of existence. You will never see what 'really' creates Plato's cave shadows.

There's an isomorphism to Gödel's incompleteness theorem, I think: no system of experience or self-awareness can ever be totally securely founded because the foundations themselves must rest on something that is not accessible to that system.

Hofstadter and Dennett (in "The Mind's I", and later in Hofstadter's own "I am a Strange Loop") found a good partial solution to this conundrum in that feedback loops don't require 'foundation' in order for them to be self-sustaining, and even bring about some emergent properties self-awareness. It's the only reasonably argued way out I've come across to address the Hard Question of consciousness.

Hugo said...

Christopher Gray said "What happens to Descartes when he's asleep? Does he stop 'existing' simply because his own point of view - and ability to experience his own performance - stop existing? This inconsistency is what has always bothered me about Descartes' argument."

That is not an inconsistency. Descartes' argument is that his thoughts imply his existence. Lack of his thoughts would not imply his non-existence.

Hugo said...

P.S. If there is a problem with "I think therefore I am", it is not that the conclusion does not follow from the premise; it is that Descartes cannot know that the premise is true.

If the premise is true, the existence of an "I" is presupposed. "I am" does follow from "I think".