AKA
I think therefore I am.
How and why is the process of thought a proof of existance?
As opposed to?
I think this goes to the extreme philosophical debate of being able to “prove” if anything actually exists. Perhaps I am plugged into a computer in some lab somewhere ala The Matrix and everything I see around me is merely a computer generated fantasy of mine (or whoever runs the computer). We are all really locked inside our own heads and the only thing I can say with certainty is, “I think, therefore I am.” I may not be what I think I am…maybe I am a Little Green Man from Mars taking a holiday in my super computer that is generating the rest of the world for me but something is processing what I see so I feel confident that there is a “me” that exists.
Of course you can say the same thing back to me that you exist and I do not but really I know that is just my computer scripting you to say that. 
Can you postulate any way in which you could think and not exist?
You appear to exist but may be a figment of my imagination.
In other words, the only perception that cannot be false is that of your own existence, because the mere fact you can perceive at all proves you do.
Basically, it goes like this:
“Hmm. I wonder if I exist? Well… I’m wondering right now, right? If I didn’t exist, I couldn’t be wondering about it in the first place*. So, I do exist.”
(*It’s assumed that nonexistent objects cannot think.)
But this only tells you that there is “thinking” going on. You still can’t tell whether you’re a person or whether you’re the only thing in the universe, and you can’t tell whether you will continue to exist for any length of time. You can be certain of your existence only while you’re thinking.
So for all we know, maybe we cease to exist every time we go to sleep…
The way out of this absurd trap is to take Turing’s view on the matter, and conclude that anything that cannot be behaviorally distinguished from a sentient being is a sentient being. This relegates to the dustbin of uninteresting ideas (that is, premises from which no useful conclusion can flow) such absurdities as ‘philosophical zombies’ and the whole semi-mystical claptrap about ‘qualia’.
The problem with the Turing test is that it tests the tester, not the object. It can provide a guess on the likelihood of sentience in the tested object, but all it really tells you is how gullible (or lazy) the person applying the Turing test is.
If the Turing test is to be trusted, then I would have to say all answering machines are sentient. You’ve been tricked into believing “the voice” was the real deal, haven’t you?
Actually, that wasn’t a very complete response.
What I was trying to say is that the Turing test depends heavily on the test-giver. Some chatbots these days can already fool certain people, especially when they’re not deliberately looking for sentience. Technically, the chatbot has passed the Turing test and thus must be sentient. But the guy who wrote the chatbot knows that it isn’t. To define “sentience” in this way reduces the meaning to “able to mimic a human well” – which is not necessarily the same as being conscious and actually thinking thoughts.
But then again… what is “thought”? Sentience is meaningless until we can first define that.
So the Turing Test isn’t a proof of anything. Show me one thing in the hard sciences that is. Every method, every test, employed by the hard sciences is a means for gathering evidence, and evidence can never prove anything (ref: Karl Popper). All arguments based on evidence, as opposed to axiomatic systems, are probabalistic in nature and subject to disproof the instant disconfirming evidence comes to light. Since the result of a Turing Test is just such an argument based on evidence, the process of testing never conclusively ends.
Some probabilities are so high they are treated as 1 for the purposes of other tests. This shorthand is required for all progress, simply because we do not have time to check and recheck everything every time. Some test results remain useful even though an underpinning test result has been disproven: Star charts assume a geocentric universe, and they remain useful for navigation even after the work of Copernicus and Galileio. Thus, the results of the Turing Test we everyday apply to everyone we meet are treated as foregone conclusions simply for the purposes of social discourse and our normal routine. Even if everyone else is a zombie, things work best if we assume they are just as human as we are.
The OP deals with philosophy and logic, not science.
You mentioned “uninteresting ideas (that is, premises from which no useful conclusion can flow)”. They may be uninteresting from a hard science standpoint, but they are very interesting from a philosophical standpoint.
Yeah, but it’s of philosophical interest to know whether “philosophical zombies” are possible, even in principle. Even if no zombies actually exist, I don’t think they can be “relegated to the dustbin of uninteresting ideas” as you said.
But if you want to talk probabilities: Without knowing that all humans have true consciousness, how would you possibly go about determining the probability of a non-conscious entity violating the turing test. If it turns out that I’m the only conscious human on the planet, the probability of the turing test suceeeding when sampling from the human population seems to be only about 1 in 6.5 billion.
With regard to your last point, that things work best if we assume everyone is a truly conscious human being, this is probably true, but it doesn’t mean the possibility that they’re not loses its philosophical interest.
Why should we? We’re talking in the realms of philosophy, and here we can in fact get completely true answers to some questions. Such as the question “Do I exist?” Yes, I do; cogito ergo sum.
–Cliffy
No sir, them non-existent objects ain’t got two brain cells to rub together, bless their little hearts. Dumber than a sack of hammers.
And just to amplify on that a bit, you can’t be certain that your memories are memories of a real past that actually happened. This could be a false perception too, along with everything else. But your existence now — no wait, now — no, now — can’t be denied.
I think in Dennett’s book, Consciousness Explained, he proposes that any device capable of simulating an entire world would have to be as complicated as the entire world, so you might as well assume the world you perceive is actually out there, in some form at least approximately as it appears. It’s the least convoluted hypothesis. You’re very probably not a brain in a jar, being fed illusions of a completely fabricated world. You can assume this is so, not just for pragmatic reasons (I interact with all these “people” and go to my “job” and feed the “cat” because the dream is nicer that way), but also because it’s the more plausible assumption.
Putting it another way: the solipsists could be right — but if they are, then they don’t exist. That’ll teach 'em!
From Dark Star, where Doolittle attempts to keep Bomb #20 from exploding on the ship:
The rest of the scene can be read here. There’s also a link with the page’s author’s conclusion as to whether Bomb #20 passes Philosophy 101.
To understand what Descarte meant by cogito, ergo sum, you have to know the context of the statement.
In his Discourse on Method, Descarte describes a philosophical exercise that he once undertook (apparently to relieve the boredom of being snowed in). He sorted all of his accumulated knowledge into two classes – a) that which he had learned from his own observations (sensory input); and b) that which had been passed on to him by other people. Knowing from experience that a) one may be deceived by one’s own senses, and that b) people lie, he attempted to reconstruct a state of pure intellectual innocence. In other words, when one strips away everything that might be untrue, what is one left with? The answer, he said, was that he retained only the knowledge that he, himself, existed.
Descartes then took the exercise a little further. How did he know that he existed? Because even when separated from all the accumulated mental baggage of a fully grown (and well educated) adult, there was clearly something going on. He was thinking.
One more step. How does one know that one is thinking? This knowledge cannot be a conclusion drawn from sensory data, nor is it passed on from others. So how does one know? Descartes solved this by adding another category of knowledge to his pre-defined listing – he added intuition.
Don’t know if this helps anyone, but (assuming that I got it all right) my dearly departed philosophy prof would be proud of me for remembering all of this.
I remember reading that the philosopher A J Ayer said that Descartes could only claim “there are thoughts”. What wasn’t clear to me was whether he was merely picking a hole in Descartes’ reasoning, or he actually disagreed with the conclusion. Any of our resident philosophers care to elaborate?
Ah, but what if your mind and the thouhts it generates are only matrix computer programs?
The proof of your existance is only an illusion…a concept found in various eastern religeons.
I am not anything more than an armchair philosopher so cannot authoritatively speak to what Ayer was really trying to get at there but here is how I take what he said.
I know there are thoughts because clearly something is perceiving this thing around me called the world/universe. However, everything I see may be a lie (or not truly exist) as it could all be a hallucination or god/computer driven fantasy or what have you. As mentioned earlier I may be a brain in a jar on someone’s desk with all my perceptions being fed to me.
So, “I” may not exist as the person I think I am but I can say “something” exists that is “me” as clearly (to me anyway) my thoughts do exist…however misinformed they may be.
Hmm. Interesting, but I don’t find that particularly convincing. In dreams, for instance, stuff that doesn’t make any sense seems to make sense. It may be the same with the waking world – there might well be huge gaps in logic which we fail to perceive or forget about as soon as we see them. So the world-sim might be much less complicated than the real world would be, but there’s a correcting mechanism that fills in the blanks like your eye does in the blind spot.
–Cliffy
As I just wrote above I may indeed not be the person I think I am (ala really a brain in a jar). Everything I think I know may be a lie/illusion as you alluded to. However, something that is me is processing all this, lie or not. So, while you all may be part of my hallucination I feel comfortable in saying I do exist else what is it that is having the illusion in the first place?
If you were truly trying to simulate the entire world in one go then I agree such a system would monstrously complex. But as an avid computer gamer I know it is not necessary to simulate the whole “world” simultaneously. All that really needs to be worked on is what is in front of me at the moment. The rest of the game world can be ignored…saves on loads of processor time. When I roam to a new part the game dutifully figures what is supposed to be there and displays it.
So, if you are all my hallucination, there is no need to simulate “you” when you are out of my immedaiate perception. If I ever get back to you the illusion figures what your appropriate actions are for the moment at that time. Essentially the rest of the world can be on hold till needed.