Are there arguments you can give that are in the premise / conclusion format? Something like these (even if they are larger):
Premise: I think.
Conclusion: Therefore, I exist.
Premise: Things that do not exist, do not wonder if they exist.
Premise: I am wondering if I exist right now.
Conclusion: Therefore, I exist.
"I've always found the argument of infinite regress and the argument of circularity are the most damaging (they are impossible to argue against, as most philosophers recognise, even Russell)"
Would you consider any of these to be one of those types of arguments:
Premise: I am typing right now.
Conclusion: Therefore, I am typing right now.
1 = 1
Premise: I gave you 1 cookie.
Conclusion: Therefore, I gave you one cookie.
Premise: God wrote the Bible.
Premise: The Bible says God exists.
Conclusion: Therefore God exists.
I took quick look at Wiki to see if they had their own example and the example they gave for a circular argument was:
Premise: Wellington is in New Zealand.
Conclusion: Therefore, Wellington is in New Zealand"
It states that this does not prove that Wellington was in New Zealand. It is not objective evidence (which I agree with), such as:
Premise: I was not at the scene of the crime.
Conclusion: Therefore, I was not at the scene of the crime.
I agree that this is not objective evidence. On the same token if I tell you that "I am wondering if I exist or not", that does not prove to you (it's not objective evidence) that I am actually wondering that right now... or that I actually exist. But logic isn't so much about true/false, than it is about valid/invalid. When I am thinking to myself, I can use reasoning to infer that I exist through my own subjective experience, even though it would not prove it to anyone else other than myself (it's only subjective, not objective). The logic is valid, but the premise may be true or false, and thus the conclusion may be true or false even if the reasoning is valid. For example:
Premise: All cows are solid brown.
Premise: Diane is a cow.
Conclusion: Therefore, Diane is a cow.
This argument is valid, but is not true. Since experiences are subjective, only I can know for certain whether I am thinking right now, no one else knows that and so I cannot prove that I am thinking or that I exist to anyone else but myself.
"I'm afraid not as such arguments aren't designed to be expressed in such a format and as any valid conclusion is a claim to knowledge, which Sextus denies. There is the same issue for any valid premise."
I am not sure if I quite understand what you're getting at. But it reminds me of Gödel's incompleteness theorems, which as far as I can remember, demonstrate that you cannot even prove basic arithmetic. If something like 1+1=2 has such issues, then why not "I think, therefore I am"? In this sense, I would agree that we cannot give proof objective or subjective proof of our own existence using a system of symbols. I believe that I exist no less than I believe 1+1=2, even though I admit we have yet to show a symbolic system (strings of symbols and a symbolic agent that can decode them) can be used to create infallible conclusions.
note: Gregory Chaitin expanded on Godel's incompleteness theorems, he has some interesting reads.
"But to say I am based on my thinking presupposes I cannot think if I don't exist and that I am thinking; how can I prove either of these assumptions and do so independently of each other?"
At least part of this come across to me as an issue with semantics. Every single word we define is not a true/correct/valid or false/incorrect/invalid definition. You can define "existence" as a flavor of ice cream or the color of the sky. We completely makeup definitions. Our language is completely made up. If one defines non-existence in such a way that it excludes things that cannot think, I don't see a problem with this, anymore than I see a problem with defining "red" as electromagnetic radiation between 630–740 nanometers (inclusive). Yes, it's arbitrary, and different sources may give you a slightly different range (we even say cordless phones and WiFi use radio waves even though they use the same hertz/wavelengths as microwaves)... but that's just the nature of language. Once we agree that (x) symbol has (y) definition (like in math), we can proceed to make statements about their relations to other symbols. I don't bother to define existence or red before making an argument using these words, because I assume everyone is probably on the same page... which perhaps some of us are not.
Langue itself seems to be based on what you could call circular reasoning.
I define ____ as _____
Therefore, I define ____ as _____
I wouldn't use this reasoning to prove or disprove someone killed somebody, but if I am adding and subtracting, stating that 1=1, or using some language to communicate with someone else, then it works just fine. Even logical fallacies are not always fallacies in a certain context. They're not a clear cut as some would believe. If someone appeals to authority or credibility (or an ad hominem) to argue that their claim is false or invalid, that is a logical fallacy. But if your conclusion is about their credibility, then it's not a logical fallacy.
"I think the conclusion there should rather be that Diane is brown"
Ya that was what I meant to say haha
I know I didn't address everyone you said, but I am trying (at least a bit) to limit the size of my response. I'll look up Nagel's bat, I am not sure if I've heard of that before.
"it appears that the only real difference between us is that you at least certain truths, even if they aren't commutable, while I don't think I do (I say I don't think I do as to say I do not accept such truths would itself be a truth which I accept). Although maybe I'm wrong there."
I think I can agree with that. For the sake of argument, imagine we spoke a very primitive language that was very limited (limited in kind of the same way that propositional logic is limited). With such a language we would not be able to communicate some truths. Perhaps we have yet to develop a language that can (Lojban has some advantages to natural languages), or perhaps language is doomed to always have such limitations. Or maybe it's a much deeper issue.
Once you really start digging deep, you hit this point where your arguments against someone else's arguments disable your own. For example: If someone says that language or symbolic thought cannot be used to represent any truths, you are immediately disproving your own argument. Language is so much more complex than I think most people ever knew. A lot of people thought our progress in developing A.I. was going to be much quicker, but creating something that can encode and decode the English language proved to be much more difficult than expected.
"I can define myself as 100 years old; or I can define that which thinks as existing. My doing so, however, does not make that which thinks exist, or think, for that matter, or at least as far as I know it doesn't."
I agree with you... I think to at least some extent. Stating something doesn't make it so. If we both define existence, thinking, 100 years, and red the same way, and use our words+definitions to make a valid argument, it doesn't make it true.
"So do you mean that even if something is circular it works just as well?"
Well I think saying:
Premise: I believe I am human.
Conclusion: Therefore, I believe I am human.
Is valid. I also think:
Premise: The Bible is the word of God.
Premise: The Bible says god exists.
Conclusion: Therefore, God exists.
Is a valid argument, but I think the 1st premise is false, which is needed to support the conclusion. I also believe that:
Premise: I am wondering if I exist.
Conclusion: Therefore, I am existing (at least right now, there is the issue of continuation of self).
Is also an argument that we can both judge as valid, provided we both define the Bible, God, existence, wondering/thinking in enough the same way that our personal definitions don't change the validity of the arguments.
"Oh and Nagel was an article which bemoaned the impossibility of knowing what it is like to be a bat."
I can agree with that statement. I don't think any of us can completely know what it's like be any other thing. From a scientific perspective mirror neurons help us relate to others, but only to an extent. If someone is in pain, certain parts of your brain may light up in the same ways theirs do, but not map the pain so specifically. For instance, if you're sympathizing with someone that hurt their hand or knee, your brain may actually replicate the activity of their brain to a certain extent, but not completely.
edit: lots of little errors I had to fix in this one
"Still getting back to proving one exists is ever more difficult to do, certainly to others and perhaps yourself, when one recognises the limits of language an that an argument may be valid but not true"
Definitely! I would say proving that one exists, and that proving or disproving anything for that matter is "ever more difficult to do" when you starting getting into the limits of language.
"Why are you sure you exist?"
Basically... I guess it boils down to when "I am wondering if I exist" I believe "I am wondering if I exist" as I do it. And my definition of the word "existence" includes anything that wonders or questions its existence. Even if in reality... I... as I type this... popped into existence right now with memories intact of the entity that began to write this before me, I would still say I exist as I am thinking about it, even if I do not exist in the way that I think I do.
I suppose the fact is that what some believe, including what Descartes believed concerning the argument "I think, therefore I am" is no necessarily how I interpret it. Perhaps Descartes... or most likely at least some other people, see it as a validation of continuation of self as well. While we may not interpret or agree with the argument, as we take more time to describe out beliefs to each other, I find that we agree on more that one would typically assume we do. Perhaps most of our disagreement lies more in semantics than actual reasoning.
"but I know the continuity of the 'I' was a early criticism of Descartes, so I assume he was oblivious to it. In his writings that I have read I see no reference to it."
Oh wow, so I may be on to something. Thanks for sharing that with me.
"But why do you consider thinking things as existent?"
The same reason I consider red right above infrared on the EMR spectrum or apples to be fruit or symbolic thought to be a type of thinking, I consider thinking to be a property of existing, circumference to be a property of a circle, and that pi is defined as the ratio of a circle's circumference (C) to its diameter (d). I realize that all of these terms were made up and arbitrary, and that we use them to communicate our beliefs, experiences, etc... Maybe when I look at a red apple, what I see as red is what you see as green. Either way I know that, as I am experiencing it, that it's happening (I am experiencing it).
I am just not 100% sure that when I use a string of symbols such as "red" to communicate my experience (encoding), that you're decoding it in such a way that it communicates to you the same color experience that I am experiencing. As I am experiencing something the existence of that experience (that fact that I am experiencing it) is verified to me as it happens (as I am experiencing it at that moment), even if the terms I use to describe that experience are terms we made up to help us communicate our experiences to other people.
Perhaps a somewhat more thorough argument would add a bit of definition and constraints.
Premise: Something that does not exist right now would NOT believe it exists right now.
Premise: Right now I believe that I exist.
Conclusion: I exist right now.
Perhaps I will cease to exist right after this temporal thought/experience. Perhaps I poofed into existence just long enough to have this thought/experience and then poofed out of existence...
I definitely don't believe I exist because it gives me some sort of comfort, as it surely doesn't prove I have existed over a longer period of time than the concurrent thoughts/experiences about my existence.
Without being able to prove continuation of self, the experience of acknowledging that I am having an experience as it happens doesn't verify much else to myself, and nothing to anyone else.
Cute... jumping into a thread without actually reading it first. This conversation was going so well...
"saying "I know I exist", is like pointing at a tree and saying "I can see that tree, therefore it exists".
Nope. Having the visual experience of a tree just proves that you're having a visual experience of a tree... you could be in a simulated reality like The Matrix or Total Recall. In some instances you may be dreaming.
"Point is do we exist in the material world (earth) or the spirit world?"
Your point is only relevant if someone were actually saying "I know I exist in the material world" or "I know I exist in the spirit world". Saying "I exist" doesn't assume either one.
"How can you consider existence a property of a thinking thing (even assuming you are thinking, or experiencing) without falling back on the apparent fact you are thinking, experiencing and therefore existing, which is the matter under question?"
Does this seem close to what you're suggesting... or do you at least agree with it?
Premise: You cannot know if you're experiencing without 1ST assuming that you're experiencing.
Conclusion: Therefore you don't know if you're experiencing anything.
"The problem there is the same; how do you know your premises are true without invoking the conclusion?"
Premise 1 is basically just a definition (perhaps it could have been worded better), and defining words isn't a true/false statement, just an assignment, such as 1 = one = uno.
Premise 2 I know is true because it's happening right now. Even if I were to agree with you that it may NOT actually be happening right now, I am still agreeing to something , and I classify agreeing as a type of experience, it's just the word I choose.
I don't believe that the only way to prove that something is true is to put it into the format of Aristotle's syllogism and not invoke the conclusion in its premise (especially a subjective experience). If this is what we disagree on, maybe Descartes argument is not the best example to use.
Premise: In the English language "red" is defined as EMR around 650nm.
Conclusion: Therefore, the definition of "red" in the English language is EMR around 650nm.
Would you say that not only we cannot know if we exist, that we cannot know the definition of any word we use?
Going back to this:
"How do you know your premises are true without invoking the conclusion?"
If this is the case, can you demonstrate that your conclusion is true, that we cannot know if we exist in such a way that your argument holds more water than the one Descartes provided? Or perhaps at this level of critique we cannot really say anything that is 100% true.
Perhaps that's why... Sextus? does not put his arguments in the premise/conclusion format, because he could no more justify his position than Descartes could justify his using the premise/conclusion format.
the fact that we can actually ask ourselfs a question like that, is enough proof that we exist .. something that doesn't exist.. rocks may not think about such things but we can feel them with our hands to prove eachothers presence.. win win situation for you and the rock o/