Thread: Discussion: "Brain In A Vat" Theory

the brain in a vat theory is a dead end question unless the human being has a spirit. for example, a brain is still a body part therefore the only way to ever know you are a brain in a vat is to have an outer body experience. I also want to say dreaming would free you from the control of the vat as well, as the dream is entirely created by the brain and not the electrical impulses fed to your brain from an outside source

otherwise, the vat would be your reality

The cogito is the probably the only thing that cannot be flawed.

The point is that, you think, therefore you are, is that whatever you think, whatever you are, you know that YOU are thinking, therefore, you are whatever that is. Even if a demon is manipulating with his rationality, he still thinks, and therefore, he can be sure that he is. Furthermore, I would say the vision analogy is inappropriate and does not convey the cogito whatsoever.

Well, no.

The skeptical scenario is this: suppose there is a demon decieving me, and suppose this demon has the powers to meddle with my reasoning. I cannot therefore trust my own ability to think - I might think 1 + 1 = 2 is correct, when actually it isn't, and the demon is fooling me. This argument can take whatever form - brain in the vat, matrix etc.

Descartes tried to solve this by stating that the very fact that I am thinking at all proves that something exists to do the thinking. But this is circular as I stated before - you are using the very faculty under scrutiny to verify whether it is being decieved. This is fellacious.

The very statement 'I think' is itself a thought, not to mention the conclusion 'therefore I am,' which is a direct appeal to reason. But in this skeptical scenario, rationality cannot be used because it is the very faculty under doubt.

I understand the appeal of the Cartesian cogito. Cartesianism holds that the 'I' can be known through introspection. This introspection is the 'I think.' Yet again I must stress that thinking cannot be trusted as a means of defeating this skeptical scenario.

The vision analogy is not inappropriate at all.

If I were to test whether I was visually hallucinating a pink elephant in front of me, I would have to rely on another faculty other than vision to test this. Perhaps I might reach out and see if my hand goes through it. Testing whether the pink elephant I see in front of me is real by looking at it is circular.

If I suspected that I was a brain in a vat, or that a demon was fooling my perception including my reasoning, I could not use 'thinking' as a means of proving that I do exist. I would have to use some other means, but because every other faculty depends upon thinking in some way, there is no escaping it.

I also want to say dreaming would free you from the control of the vat as well, as the dream is entirely created by the brain and not the electrical impulses fed to your brain from an outside source

Well, the vat could be feeding your brain the electrical pulses to fool it into thinking it is dreaming. No different from fooling it into thinking it is awake, or any number of things.

Originally Posted by Roller

Well, no.

The skeptical scenario is this: suppose there is a demon decieving me, and suppose this demon has the powers to meddle with my reasoning. I cannot therefore trust my own ability to think - I might think 1 + 1 = 2 is correct, when actually it isn't, and the demon is fooling me. This argument can take whatever form - brain in the vat, matrix etc.

Descartes tried to solve this by stating that the very fact that I am thinking at all proves that something exists to do the thinking. But this is circular as I stated before - you are using the very faculty under scrutiny to verify whether it is being decieved. This is fellacious.

The very statement 'I think' is itself a thought, not to mention the conclusion 'therefore I am,' which is a direct appeal to reason. But in this skeptical scenario, rationality cannot be used because it is the very faculty under doubt.

I understand the appeal of the Cartesian cogito. Cartesianism holds that the 'I' can be known through introspection. This introspection is the 'I think.' Yet again I must stress that thinking cannot be trusted as a means of defeating this skeptical scenario.

The vision analogy is not inappropriate at all.

If I were to test whether I was visually hallucinating a pink elephant in front of me, I would have to rely on another faculty other than vision to test this. Perhaps I might reach out and see if my hand goes through it. Testing whether the pink elephant I see in front of me is real by looking at it is circular.

If I suspected that I was a brain in a vat, or that a demon was fooling my perception including my reasoning, I could not use 'thinking' as a means of proving that I do exist. I would have to use some other means, but because every other faculty depends upon thinking in some way, there is no escaping it.


Well, the vat could be feeding your brain the electrical pulses to fool it into thinking it is dreaming. No different from fooling it into thinking it is awake, or any number of things.

Alright - how would explain this then:

Even if my faculty of reasoning is being manipulated by a demon, even if my rationality is the result of a malicious demon; how is it that that means that I do not exist? I ask because what you are saying is that, even though I think, I am not. Are you denying the cogito and saying that it is completely wrong or that we only sort of exist? If that is the case, how?
~

Alright - how would explain this then:

Even if my faculty of reasoning is being manipulated by a demon, even if my rationality is the result of a malicious demon; how is it that that means that I do not exist? I ask because what you are saying is that, even though I think, I am not. Are you denying the cogito and saying that it is completely wrong or that we only sort of exist? If that is the case, how?

It simply cannot be used to prove that we exist. The statement "I think" is a form of thinking itself - how does one know one is thinking? Through introspection, which is a form of thinking. The only thing that matters is that in the skeptical argument, thinking itself cannot be trusted at all as a means of assuring existence. One thing epistemology seeks to do is to defeat the skeptical argument, and Descartes fails to defeat his own skeptical argument.

haha i tried to bring this up in the forum some time ago but i couldn't find anything on it... i think i kept looking up "brain in a bucket" and didn't get any good leads.

good theory... as sound as most.

Originally Posted by Roller

It simply cannot be used to prove that we exist. The statement "I think" is a form of thinking itself - how does one know one is thinking? Through introspection, which is a form of thinking. The only thing that matters is that in the skeptical argument, thinking itself cannot be trusted at all as a means of assuring existence. One thing epistemology seeks to do is to defeat the skeptical argument, and Descartes fails to defeat his own skeptical argument.

Please explain how, I am curious. Even if my thinking is completely manipulated and maliciously deceptive, I can still prove to myself that I think.

Just to note that I never thought this proves to others that you think. I do not think anything can prove to other people that you think. However, the cogito can prove to yourself that you think.

If not - please explain how - I have yet to see a cogent argument.
~

Please explain how, I am curious. Even if my thinking is completely manipulated and maliciously deceptive, I can still prove to myself that I think.

Proving is an act of reasoning. You can think, but any argument applied to this 'thinking' fails, because of the said doubt in one's reasnoning faculties. To use one's cogito to prove anything, even to oneself, would go something like this:

a) I am thinking.

b) All thinking things exist.

c) Therefore, I exist.

But this is a form of argument, which requires use of rationality. Proceeding from the premises to the conclusion is an act of rationality, which we cannot use at all given the skeptical scenario. In fact, the simple construction of a premise is also an act of rationality. To construct premise a) into a belief uses rationality.

Not wanting to sound up-myself here, but I'm studying a course in epistemology at the moment and philosophers are still trying to provide a plausible argument for existence. The Cartesian Circle usually refers to Descartes' attempt to prove existence through an appeal to God.

In Foundationalism, Epistemic Principles, and the Cartesian Circle, James Van Cleve states,

"The problem of the Cartesian Circle arose for Descartes becasue he appeared to commit himself to each of the following propositions:

1) I can clearly know (be certain) that (p) whatever I perceive clearly and distinctly is true only if I first know (am Certain) that (q) God exists and is not a deceever.
2) I can know (be certain) that (q) God exists and is not a deceiver only if I first know (am certain) that (p) whatever I perceive clearly and distinctly is true.

Obviously, if (1) and (2) are both true, I can never be certain of either p or q. To be certain of one I would already have to be certain of the other" (55).

This is the formalised construction of the Cartesian Circle. Formulating this in terms of the cogito issue would be:

1) I can can clearly know (be certain) that (p) whatever I rationalise clearly and distinctly is true only if I first know (am certain) that (q) I exist and am thinking clearly.

2) I can know (be certain) that (q) I exist and am thinking clearly only if I first know that (p) whatever I rationalise clearly and distinctly is true.

Again, as in Van Cleve's case, if 1 and 2 are true, I cannot hold both P and Q. Both P and Q depend upon the other first existing. This is the Cartesian Circle.

Originally Posted by Roller

Proving is an act of reasoning. You can think, but any argument applied to this 'thinking' fails, because of the said doubt in one's reasnoning faculties. To use one's cogito to prove anything, even to oneself, would go something like this:

a) I am thinking.

b) All thinking things exist.

c) Therefore, I exist.

I agree with the rest of what you said except for what I quoted here.

Here is how I would standardize the cogito:

a) Whatever I am, I am able to think this.
b) Therefore, I exist.

I do not think it should be separated into "all thinking things exist" but merely that you know that you are thinking, you are aware of your thinking. Thus, whatever you are, you exist.

We could cast doubt on the premise and say that even the rationality is manipulated or inauthentic. However, I can still then show to myself that I think. There is no reasoning required to do this - you are thinking right now, and because of that, you know you exist - whatever you may be or be the result of.

Are we on the same grounds in that matter..?
~

I agree with the rest of what you said except for what I quoted here.

Here is how I would standardize the cogito:

a) Whatever I am, I am able to think this.
b) Therefore, I exist.

Sorry, but that argument is invalid. I formulated the argument as I did because it is a valid way of putting the argument.

a) I think.

b) All thinking things exist.

c) Therefore, I exist.

This argument is valid because the premises a) and b) force the conclusion. If a) and b) are both true, it is impossible for c) not to be true. Your formulation of the cogito argument is invalid because the premise a) does not force the conclusion b). You need the 'all thinking things exist' premise, otherwise it could be possible that you are a thinking thing that does not exist (regardless of whether or not this is possible, it is merely a case of the logic of the argument.)

But yet again, I stress that existence cannot be proven through this argument. Even through your formulation of it:

a) Whatever I am, I am able to think this.
b) Therefore, I exist.

No matter how you formulate the argument, you always need a therefore or a because, which are both examples of rationalisation, or thinking. The skeptical scenario we are replying to here - either Descartes' demon, or the brain-in-the-vat etc - specifies that we cannot trust our reason.

Even if premise a) is granted, which I doubt it can be, making any sort of conclusion from this is an act of reason. Nothing can be trusted after the 'therefore' and nothing can be trusted before a 'because.' Any conclusion that is reached by reason cannot be trusted.

I can see where you're coming from, though, and I used to have exactly the same intuition. If something is thinking, then there must be something there to do the thinking, right? This is ordinarily quite a good intuition, the only problem it has is that it cannot defeat the skeptical argument - in fact no argument so far has been able to defeat it. Some philosophers argue that we're affording the skeptical argument too much of an advantage, but that's a whole different discussion.

Originally Posted by Roller

I can see where you're coming from, though, and I used to have exactly the same intuition. If something is thinking, then there must be something there to do the thinking, right? This is ordinarily quite a good intuition, the only problem it has is that it cannot defeat the skeptical argument - in fact no argument so far has been able to defeat it. Some philosophers argue that we're affording the skeptical argument too much of an advantage, but that's a whole different discussion.

This is where you mistakenly reading my posts. I am not saying that because something is thinking then there must be something there to think it, I am trying to show you that the cogito is a tautology but can only be applied to individuals who think it - no one else.

I will best show you the arguement in its prime form:
- I think.
- Therefore, I think.
Or
- I exist.
- Therefore, I exist

There is no other premises required because there is nothing else required. The conclusion does not need any more support than this. You could perhaps argue the second formulation and debate over what constitutes existance but the point I am trying to make is that you can think, to yourself, "I exist", and from that conclude, "I exist". There is nothing else to it besides that. You can prove to yourself that you exist by simply thinking. Whatever it may be, even if your rationality is manipulated beyond belief, even if your reasoning is inauthentic, then it only means you exist, but with inauthentic reasoning. I still exist, I know that about myself, any form of manipulation does not take away from my knowing that I exist.

Just do not misinterpret what I am saying to; all thinking things exist, or anything that think exists. What the cogito is intended for is the individual thinking it and no one else.
~

It seems we are at a stalemate here.

I see the tautological nature of what you are proposing, but I still disagree with your argument. I have no objection to your first premises. I have no doubt that a person can claim to be thinking, but as soon as the person tries to make a conclusion from this they are trapped by the skeptical argument.

here is no other premises required because there is nothing else required. The conclusion does not need any more support than this.

I disagree with this though. The formulation I described in my previous post is a valid deductive argument. The argument you are describing is inductive, meaning that it cannot prove anything. The second premise that I added is required to make the argument deductive, even if it is only being used by a subject to prove existence to themselves. I think that you actually are using this argument without realising it.

the point I am trying to make is that you can think, to yourself, "I exist", and from that conclude, "I exist". There is nothing else to it besides that. You can prove to yourself that you exist by simply thinking.

Let me explain. I assume we both agree that one cannot prove existence by speaking the words 'I exist,' because a computer could be programmed to record and play back the sound of the words 'I exist.' Similarly, one cannot prove existence by writing 'I exist.' That is granted, and I know that you are not arguing this at all. What you are arguing is that the act of thinking 'I exist' proves existence. Sorry if it sounds like I'm stating the obvious here, but stay with me. So therefore, the first premise of your argument would be:

1) S ('S' here representing the subject) thinks 'I exist'
2) Therefore, S exists.

But this formulation still needs some work. What if the subject thinks 'I like spaghetti' for example? What you are arguing is that the act of thinking, no matter what the thought is, can prove existence. So we need to modify the first premise to:

1) S thinks
2) Therefore, S exists.

Again, sorry if I'm stating the obvious. I'm trying to show why the argument you are proposing actually takes the form that I explained in my last post. The above formulation seems intuitive enough, and I don't think you would protest at the above formulation. It is, however, an incomplete argument because the conclusion 2) in no way follows from the premise 1). Keep in mind that what I mean by this is that the premise 1) and the conclusion 2) when read in complete isolation, are not valid. I'll construct an analogous argument to demonstrate this:

1) S breathes.
2) Therefore, S is a 21-year-old male from Austria.

As you can see, this is an entirely invalid argument. I take it that all 21-year-old males from Austria breathe, but this doesn't mean that all breathing things are 21-year-old males from Austria. This is why the second premise is needed the Cogito argument:

1) S thinks
2) All thinking things exist
3) Therefore, S exists.

This has nothing to do with proving one's existence to other people, it is simply the correct formulation of the argument. If I were to use my thinking to prove my existence to myself, this is the argument that I must use.
Sorry to get everything caught up in logic here, and I'm not meaning to say that I know your argument better than you do yourself or anything, just that this is how the cogito argument has to be if it is to prove anything deductively. This formulation makes sure that there are no thinking unexistent things.

The reason that this argument does not defeat the skeptical argument is that it relies on reason. Every argument relies on reason. But under the skeptical argument, reason is not to be trusted. There is no way that the conclusion 3), or any other conclusion can be sound. You can think as much as you like, but for the fact that you are thinking to mean anything you have to use reason. Anytime you use a therefore, you are using reason, and because the faculty of reason is under question in the skeptical scenario, any conclusion whatsoever can not be trusted.

Even if you still disagree with my inclusion of the second premise, and even if you formulate the argument as you do in your last post:

a) I exist.
b) Therefore, I exist

You cannot be certain. Under the skeptical scenario, you could not even argue:

a) I am blue
b) Therefore, I am blue

Because all arguments rely on logical reasoning, and in this scenario reasoning is under seige.

Whatever it may be, even if your rationality is manipulated beyond belief, even if your reasoning is inauthentic, then it only means you exist, but with inauthentic reasoning.

But you have no way of knowing that thinking qualifies you for existence. It is not, like you said, a question of whether thinking things exist or not, it is a question of whether they can be shown to exist. And the cogito argument relies on reasoning to prove existence, which is inherently circular. There is no reason to believe ANY conclusion.

Originally Posted by Roller

1) S thinks
2) Therefore, S exists.

Again, sorry if I'm stating the obvious. I'm trying to show why the argument you are proposing actually takes the form that I explained in my last post. The above formulation seems intuitive enough, and I don't think you would protest at the above formulation. It is, however, an incomplete argument because the conclusion 2) in no way follows from the premise 1). Keep in mind that what I mean by this is that the premise 1) and the conclusion 2) when read in complete isolation, are not valid.

Something which does not exist cannot think. Anything which thinks obviously exists. I think you're using some strange definition of 'existence' or something. How can you doubt the existence of something which is able to form a thought?

Originally Posted by Roller

But you have no way of knowing that thinking qualifies you for existence. It is not, like you said, a question of whether thinking things exist or not, it is a question of whether they can be shown to exist. And the cogito argument relies on reasoning to prove existence, which is inherently circular. There is no reason to believe ANY conclusion.

Again, your definition of 'exists' is very strange. You don't have to 'qualify' to exist - you just have to BE. Anything which thinks clearly IS - even neurologically speaking, a thought is action among neurons. Therefore, if you are able to formulate a thought, then you must have neurons and so you must exist physically.

I don't see any room for argument here. Are you suggesting that things which do not exist are able to think?

Originally Posted by Roller

It seems we are at a stalemate here.

But you have no way of knowing that thinking qualifies you for existence. It is not, like you said, a question of whether thinking things exist or not, it is a question of whether they can be shown to exist. And the cogito argument relies on reasoning to prove existence, which is inherently circular. There is no reason to believe ANY conclusion.

I understand the nature of your arguement. However, there are problems in how you are forming it.

Most problematic - existance does not depend on logical justification. You seem to be arguing that, in order to prove existance, we must rationaly justify it with a logical process. Looking at it from this perspective, it is impossible to prove existance, even to oneself.

There is no logic required, rationalized, or anything to prove to yourself that you exist. The very fact that you exist can prove to yourself, without any reasoning, logic, standardized thought process - that you exist.

When you isolate the ability to prove existance in language and logic, you isolate it to an impossibility.

Furthermore, consider this:
- I think
- All thinking things exist
- Therefore, I exist

Before this arguement can be valid, we must prove the truthfulness of the second premise. When we do that intuitively (because we know that we exist, this being the person thinking it only), we have already proven the existance. This arguement is merely a means to explain the mental process you can individually take to show yourself.

The Cartesian Circle is the problematic illogical process of relying justifying existance in the logical world alone. Whereas, I think we can both agree that logic can never do such a thing. If you disagree and want to read my reasoning why (which I imagine you agree), read my thread "Tractaus; Language is not Transcendental".
~

Originally Posted by juroara

the brain in a vat theory is a dead end question unless the human being has a spirit. for example, a brain is still a body part therefore the only way to ever know you are a brain in a vat is to have an outer body experience.

True, true. Shame there's no spirit eh.

Originally Posted by juroara

I also want to say dreaming would free you from the control of the vat as well, as the dream is entirely created by the brain and not the electrical impulses fed to your brain from an outside source

No. you fail.

The experiances your dreams are based on would be simply what the impulses had fed your brain, hence they would be entirely restricted by the impulses.

There is no freedom to be had here.

Originally Posted by O'nus

I understand the nature of your arguement. However, there are problems in how you are forming it.

Most problematic - existance does not depend on logical justification. You seem to be arguing that, in order to prove existance, we must rationaly justify it with a logical process. Looking at it from this perspective, it is impossible to prove existance, even to oneself.

There is no logic required, rationalized, or anything to prove to yourself that you exist. The very fact that you exist can prove to yourself, without any reasoning, logic, standardized thought process - that you exist.

When you isolate the ability to prove existance in language and logic, you isolate it to an impossibility.

Furthermore, consider this:
- I think
- All thinking things exist
- Therefore, I exist

Before this arguement can be valid, we must prove the truthfulness of the second premise. When we do that intuitively (because we know that we exist, this being the person thinking it only), we have already proven the existance. This arguement is merely a means to explain the mental process you can individually take to show yourself.

The Cartesian Circle is the problematic illogical process of relying justifying existance in the logical world alone. Whereas, I think we can both agree that logic can never do such a thing. If you disagree and want to read my reasoning why (which I imagine you agree), read my thread "Tractaus; Language is not Transcendental".
~

I agree with Onus on this. The thing with cogito, is that the mere process of doubting the cogito, proves the cogito, which is where it's strength lies essentially.

Equally you can use this with a empiricist point of view, and take into account experience as some sort of proof. For example;


-I am looking at a red cloth

-The red cloth may be an illusion, it may be a creation of my mind, it may not be real.

-Even so, I am experiencing RED. This is entirely undoubtable and self justifying.

-The experience of RED is taking place, in some form, even if there is nothing physical, I am still experiencing RED.

-Hence in order to experience I must be.

-This fits snugly in with the rationalist foundationalist argument of Cogito ergo sum.

Sorry it's taken me a while to respond, I've been pretty busy the last few weeks.

Something which does not exist cannot think. Anything which thinks obviously exists. I think you're using some strange definition of 'existence' or something. How can you doubt the existence of something which is able to form a thought?

Knowing you exist and existing are different things. The brain in a vat hypothesis and Descartes' Meditations are about knowledge. The question is not about existing itself, but a means by which existence can be 'known.' My point in my previous post is that for 'I think therefore I am' or the cogito to count as knowledge, there is an implied second premise, 'all thinking things exist.' This has nothing to do with whether thinking things do or do not exist, but I am merely demonstrating the hidden part of the cogito argument to show just how much reasoning is involved. I'm not suggesting that there are things that do not exist which think.

Most problematic - existance does not depend on logical justification. You seem to be arguing that, in order to prove existance, we must rationaly justify it with a logical process. Looking at it from this perspective, it is impossible to prove existance, even to oneself.

That, in a nutshell, is exactly the problem. The cartesian cogito cannot defeat the skeptical argument from ignorance as a means of proving knowledge of the fact 'I exist.' This comes mainly from problems of the definition of knowledge. There is a general consensus in the field of epistemology that knowledge at least requires justified, true belief. This has been shown by Gettier to not be sufficient, but these requirements are at least neccessary.

So, by looking at existence through the epistemic proof requirements of justified, true belief (henceforth JTB) we can see it as:

What does it take for me to know I exist?
I need to have the belief 'I exist.'
This belief needs to be true.
This belief needs to be justified.

Ok, so we're assuming that using the cogito argument, person S already believes that they exist. The truth value, person S would claim, is the fact that S is thinking, or the cogito. Now we reach the justification for the belief, which is reasoning. Again, the same problem: reasoning is the faculty under investigation and doubt, so cannot be used to prove knowledge.

There is no logic required, rationalized, or anything to prove to yourself that you exist. The very fact that you exist can prove to yourself, without any reasoning, logic, standardized thought process - that you exist.

I disagree with this. I haven't read Wittgenstein, but I'll have a look at your other thread in a bit. It is simply that the justification for existence as concieved through the cartesian cogito relies upon reasoning. Ultimately, all justification relies upon reasoning, and reasoning is part of justification. You cannot have belief without justification.

-The experience of RED is taking place, in some form, even if there is nothing physical, I am still experiencing RED.

How do you know you are experiencing RED? Through introspection, which is a form of thought.

-Hence in order to experience I must be.

This belief is justified by your previous points. Justification, however, is a form of rationalisation, which makes the argumetn circular against the particular skeptical argument.

Descartes' Skeptical Scenario - Rational Doubt:

1. What if I am being decieved? What if when I think that 2 + 3 = 5 I am wrong, and my rational thinking is being tricked by a demon?

As you can see, any reply to this that relies upon reasoning in any way becomes circular. Sorry for repeating this point but I want to make it entirely clear.

Justification for 'I think, therefore I am' is that 'I am thinking, all thinking things exist, therefore I exist.' The justification requires rationality, which is under doubt, and therefore becomes a circular means of proving the belief 'I exist' is knowledge. For a belief to be knowledge it must be justified, true and believed.

The cogito is circular, and therefore does not offer proof that we know we exist.

Originally Posted by Roller

Justification for 'I think, therefore I am' is that 'I am thinking, all thinking things exist, therefore I exist.' The justification requires rationality, which is under doubt, and therefore becomes a circular means of proving the belief 'I exist' is knowledge.

Rationality is not under doubt, existence is.

The awareness of anything at all necessitates existence, because that is the definition of existence. It doesn't matter if your reasoning is correct or not, the simple fact that you're aware of your reasoning at all indicates that you exist. There is no way you could be thinking if you did not exist, therefore you must exist if you think.

Roller:

So, in synopsis of the cogito's circular reasoning:
- We believe that we exist
- We believe that we exist because we think.
- Therefore, we exist.

So, in order for the cogito to be acceptable, we must accept that we are existant beings.

Correct..?
~

Rationality is not under doubt, existence is.

It is in the skeptical scenario that Descartes proposes. The brain in the vat theory is an example of the skeptical argument from ignorance, which is:

Person S knows that P (I have hands) just in case:

Person S believes that P;
P is true;
S is justified in believing that P.

But, if person S were a brain in a vat:

Person S would believe 'I have hands'
P would be false;
S would not be justified in believing that P

If person S does not know that they are a brain in a vat, then they do not know anything. However, if they were a brain in a vat they would be experiencing life just as they are now, so S cannot know not to be a brain in a vat, so cannot be said to know anything.

Descartes' version was with a demon who is tricking him. Descartes states in his Meditation on First Philosophy:

"I will suppose, then... that some evil demon, who is at once exceedingly potent and decietful, has employed all his artifice to decieve me; I will suppose that the sky, the air, the earth, colours, figures, sounds and all external things are no better than the illusions of dreams, by means of which this being has laid snares for my credulity..."

Descartes also states:

"And, further, as I sometimes think that others are in error respecting matters of which they believe themselves to possess a perfect knowledge, how doI know that I am not also decieved each time I add together two and three, or number the sides of a square, or form some judgement still more simple, if more simple can be imagined?"

This is where Descartes introduces the doubt about his own rationality. Basically he's being skeptical by first doubting everything he percieves, and then being even more skeptical by doubting his own ability to rationalise or think. This is where the circularity of using rationality to prove one's own existence when rationality is itself under doubt.

Roller:

So, in synopsis of the cogito's circular reasoning:
- We believe that we exist
- We believe that we exist because we think.
- Therefore, we exist.

So, in order for the cogito to be acceptable, we must accept that we are existant beings.

Correct..?

Because of the cicularity of the cogito argument when faced with doubt of rationality, we have to accept the belief 'I am an existent being,' without using any rationality to prove this. But such a belief would be unjustified, which becomes a problem.

This problem mainly occurs because the cartesian cogito argument is a foundationalist account of knowledge, which itself encounters many problems. Foundationalist accounts of knowledge hold that there is some basic, foundational 'undoubtable' belief that serves as a base from which to build all other beliefs. The problem here is that for this 'basic' belief to be epistemically viable, it must be justified. If it needs to be justified, however, it cannot be a basic belief. It's a sort of catch-22 circularity.

For the cogito, 'I exist' is a belief that has to be justified. Unfortunately, the act of justification is an act of rationalisation, which is defeated by the 'doubting of rationality' argument that Descartes proposes.

What I don't want to say is that we can never be shown to exist. If I've accidentally stated that in any previous post, I revoke it. Of course we exist - by letting skepticism run amok many crazy things can happen. What I am arguing is that Descartes' cogito is inadequate to prove our existence.

Also, another point to make is that skepticism is an argument about knowledge. We exist, but the cogito argument cannot be used to show that we have knowledge of anything, let alone the belief 'I exist.' I think that other accounts of knowledge do work at showing that we have knowledge, and, therefore, allowing us to properly form the belief 'I exist.' Actual existence and knowledge of existence are slightly different.

Originally Posted by Roller

Because of the cicularity of the cogito argument when faced with doubt of rationality, we have to accept the belief 'I am an existent being,' without using any rationality to prove this. But such a belief would be unjustified, which becomes a problem.

I don't quite follow that - you're saying that since the argument doesn't hold if we doubt our rationalization, then we can't use rationalization at all?

I think it's foolish to doubt your rationality, because even the act of doubting is a rational process. You will never get outside of your flawed rationalizations and be able to correct for them if you are truly irrational. Therefore, it doesn't matter whether or not you're rational - you can't do anything about it, so you might as well just make do with what you have.

Originally Posted by Roller

Because of the cicularity of the cogito argument when faced with doubt of rationality, we have to accept the belief 'I am an existent being,' without using any rationality to prove this. But such a belief would be unjustified, which becomes a problem.

This problem mainly occurs because the cartesian cogito argument is a foundationalist account of knowledge, which itself encounters many problems. Foundationalist accounts of knowledge hold that there is some basic, foundational 'undoubtable' belief that serves as a base from which to build all other beliefs. The problem here is that for this 'basic' belief to be epistemically viable, it must be justified. If it needs to be justified, however, it cannot be a basic belief. It's a sort of catch-22 circularity.

For the cogito, 'I exist' is a belief that has to be justified. Unfortunately, the act of justification is an act of rationalisation, which is defeated by the 'doubting of rationality' argument that Descartes proposes.

What I don't want to say is that we can never be shown to exist. If I've accidentally stated that in any previous post, I revoke it. Of course we exist - by letting skepticism run amok many crazy things can happen. What I am arguing is that Descartes' cogito is inadequate to prove our existence.

Also, another point to make is that skepticism is an argument about knowledge. We exist, but the cogito argument cannot be used to show that we have knowledge of anything, let alone the belief 'I exist.' I think that other accounts of knowledge do work at showing that we have knowledge, and, therefore, allowing us to properly form the belief 'I exist.' Actual existence and knowledge of existence are slightly different.

The gnome makes a good point in response to this - you're walking into Pyrrhic skepticism now, really. We can easily doubt the existance of everything, including even that we do not even know that do not know anything - even not knowing that, etc. In this case, we cannot know our rationality is justified because, in order to do so, we have to use rationality. However, in order to show that this unrational unjustification of justifying rationality, is irrational. I think you see the problem - we can just do this forever.

The problem, I think, is that you're isolating logic and rationalism to the point where it is the only way we can prove existance. The fact is, you can undeniably prove, to yourself, that you exist by simply existing. Whatever it is that you are as an existant being, you exist. You do not need rationality to do this and you should not use it, once you start to try and prove your existance to yourself through rationality, you will step into the problem you have introduced.
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I think it's foolish to doubt your rationality, because even the act of doubting is a rational process. You will never get outside of your flawed rationalizations and be able to correct for them if you are truly irrational. Therefore, it doesn't matter whether or not you're rational - you can't do anything about it, so you might as well just make do with what you have.

I also think that it's foolish to doubt our rationality. To do so would be entirely pessimistic and defeatist. I'm not saying that we should doubt our rationality, but that Descartes' skeptical scenario argument does include the doubt of rationality, and so can only be defeated in a non-circular way, which means an argument that does not rely on rationality. The skeptical scenario is a thought-experiment, and so it does not matter whether it is true or not. It works on setting a hypothetical scenario and finding arguments and solutions to it which elucidate what we mean by certain things - in this case 'knowledge.'

The problem, I think, is that you're isolating logic and rationalism to the point where it is the only way we can prove existance. The fact is, you can undeniably prove, to yourself, that you exist by simply existing. Whatever it is that you are as an existant being, you exist. You do not need rationality to do this and you should not use it, once you start to try and prove your existance to yourself through rationality, you will step into the problem you have introduced.

Yes, and some philosophers have made this point. I can prove to myself that I exist simply by waving my arm and saying 'I exist.' The problem is having knowledge that one exists. Skepticism isn't the idea that 'nothing exists,' but the problem that 'we can't be shown to know that anything exists.' The two ideas are similar, but I think they create a lot of problem. While not being an exernalist, I think it's safe to say that things will keep on existing whether I am alive or not. However, while I am alive, the problem is, according to skepticism, that I can't be said to know that the things around me exist. Skepticism, unless defeated, holds that I can't be said to know anything at all.

I think that skepticism can be defeated - I think that we do have knowledge - but I simply think that the cartesian concept of 'self knowledge' or the cogito is not successful in defeating skepticism. This is mainly due to the foundationalist nature of cartesianism, and the criterion of knowledge itself - that of justified, true belief. Foundationalism doesn't hold as a theory of knowledge, and neither does its rival, Coherentism. I think that a hybrid of the two, using evolutionary reliablism, is the most promising way to secure knowledge and defeat skepticism.

So, in summary, I don't accept that we should continually doubt rationality. To do so would be crazy. But if a skeptical scenario such as Descartes outlines is raised, then any argument against it that relies upon rationality as a faculty and means of assuring knowledge then it becomes circular.

Originally Posted by Roller

Yes, and some philosophers have made this point. I can prove to myself that I exist simply by waving my arm and saying 'I exist.' The problem is having knowledge that one exists. Skepticism isn't the idea that 'nothing exists,' but the problem that 'we can't be shown to know that anything exists.' The two ideas are similar, but I think they create a lot of problem. While not being an exernalist, I think it's safe to say that things will keep on existing whether I am alive or not. However, while I am alive, the problem is, according to skepticism, that I can't be said to know that the things around me exist. Skepticism, unless defeated, holds that I can't be said to know anything at all.

I think that skepticism can be defeated - I think that we do have knowledge - but I simply think that the cartesian concept of 'self knowledge' or the cogito is not successful in defeating skepticism. This is mainly due to the foundationalist nature of cartesianism, and the criterion of knowledge itself - that of justified, true belief. Foundationalism doesn't hold as a theory of knowledge, and neither does its rival, Coherentism. I think that a hybrid of the two, using evolutionary reliablism, is the most promising way to secure knowledge and defeat skepticism.

So, in summary, I don't accept that we should continually doubt rationality. To do so would be crazy. But if a skeptical scenario such as Descartes outlines is raised, then any argument against it that relies upon rationality as a faculty and means of assuring knowledge then it becomes circular.

How are you defining "knowing" something? What does it take to "know" something?
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General consensus in epistemology is that knowledge is at least justified, true belief. For example:

Say person S has a proposition P, which is 'I think it's going to be hot today.'
For this to count as knowledge, person S must believe it (obviously), P must be true, and S must be justified in believing that P.
Say person S were to wake up in the morning, and while still in bed form the belief 'I think it's going to be hot today.' If there was no reason for holding this belief to be true, it would be wrong to count it as knowledge - you cannot simply randomly believe things and have them count as knowledge, even if your belief is true. Even if it was hot that day, person S would not have knowledge just by randomly coming to form that belief.

Also, take the situation where person S holds the belief 'it will be hot today,' based upon the weather report the night before, but the belief turns out to be false. Again, this would not count as knowledge - knowledge has to be epistemically viable, and we don't want to accept false beliefs as knowledge.

So for something to count as knowledge, the consensus is that it is at least neccessary for it to be a justified, true belief. I say 'neccessary' here because it has been shown by Gettier that justified, true belief is not sufficient for knowledge - the 'Gettier problem' demonstrates an example where a person has justified true belief, but we would not count it as knowledge. Since his paper on knowledge, many attempts have been made to find the 'other thing' that is needed for knowledge, but there is no consensus. A lot of debate has surrounded just what we mean by 'justification' and whether justification is internal or external, which is an extension of the Internalist/Externalist debate.

Foundationalism and Coherentism adress the regress problem: if a belief requires justification, then the justification is itself a belief, which requires justification. Foundationalism holds that justification is grounded in some 'basic belief' which provides justification to all other beliefs but does not require justification itself. Coherentism holds that a belief-system becomes justified because of the interaction and dependence of all beliefs in the system upon each other - our knowledge base is self-justifying. The trouble with these two pursuits is that one threatens infinite regress or non-justification and the other is circular.