Two Skeptical Arguments
Guest Contributor

15 March 2009

Posted by John Greco

I’ve been claiming that there are some really powerful skeptical arguments (on the show and in response to Ken's previous post).  I have also been claiming that one aspect of their force is that they do not depend on setting the standards for knowledge very high.   Here are two such arguments. 

1.  Hume’s argument.
The first is inspired by David Hume.  The argument begins with the assumption that our beliefs about the external world are at least partly based on how things appear.  For example, I believe that I am presently seated at my desk at least partly because that is the way things visually appear to me.  But that can’t be the whole story, the argument continues.  I must also be assuming, at least implicitly, that the way things appear is a good indication of the way things really are.  If I were not relying on that assumption, Hume argues, then the fact that things appear to me a certain way would not be a reason to think that they are that way.  But now how am I to justify this assumption about the reliability of appearances?  How can I know that the way things appear is a good indication of the way things really are?  According to Hume, there is no way to justify that assumption.  For example, suppose I were to rely on appearances, reasoning that, as far as I can tell, the way things appear to me appear to be a reliable indication of the way things really are.  This, of course, would be to argue in a circle, taking for granted the very thing at issue.   Here is Hume’s argument put more formally.

(H)

1.    All my beliefs about the external world depend for their evidence on both a) the way things appear to me, and b) an assumption that the way things appear to me is a reliable indication of the way things really are.
2.    But the assumption in question can’t be justified.
Therefore,
3.    All my beliefs about the external world depend for their evidence on an unjustifiable assumption. (1, 2)
4.    Beliefs that depend for their evidence on an unjustifiable assumption do not count as knowledge.
Therefore,
5. None of my beliefs about the external world count as knowledge.  I don’t know anything about the external world.  (3,4)

Clearly, a linchpin of this argument is premise (2): that an assumption regarding the reliability of appearances cannot be justified.  In support of premise (2), Hume considers various possibilities for justifying the assumption in question.  One consideration that Hume emphasizes is that the assumption is itself a contingent claim about the external world.  That is, the assumption claims that sensory appearances are, as a matter of contingent fact, related to the way things are in a particular way.  This suggests that the assumption can be justified, if at all, only in the way that contingent claims about the external world are justified in general—i.e. by relying on the way things appear!  But this, of course, would be to argue in a circle, taking for granted the very thing at issue.  Here again is the reasoning in support of (2).

(H2)

1.    All my beliefs about the external world depend for their evidence on both a) the way things appear to me, and b) an assumption that the way things appear to me is a reliable indication of the way things really are.
2.    The assumption in question is itself a belief about the external world.
Therefore,
3.    The assumption depends on itself for its evidence. (1, 2)
4.    Beliefs that that depend on themselves for their evidence can’t be justified.
Therefore,
5.    The assumption in question can’t be justified.  (3, 4)

    A natural thought is that the assumption that appearances are a reliable guide to reality can be justified in some other way, perhaps by some sort of a priori reflection that proceeds independently of appearances.  But Hume thinks that this line of reasoning is a dead end.  This is because the assumption in question makes a contingent claim about the way things are—it is a matter of contingent fact, and not a matter of necessity, that appearances do or do not reflect the way things really are.  But that sort of fact cannot be known through a priori reflection.  In short, a priori reflection gives us knowledge of necessary truths rather than contingent truths. 

2.  Descartes’s argument.
The second skeptical argument is inspired by Descartes’s Meditation One, and in particular by Barry Stroud’s reading of that meditation.  To understand the argument, consider the claim that one sees a goldfinch in the garden, based on one’s observation that the bird is of a particular size and color, and with a tail of a particular shape.  Suppose now that a friend challenges one’s claim to know, pointing out that woodpeckers also are of that size and color, and also have tails with that shape.  As Stroud points out, this seems to be a legitimate challenge to one’s claim to know that the bird is a goldfinch.  More generally, if one’s evidence for one’s belief that the bird is a goldfinch is consistent with the possibility that it is in fact a woodpecker, then one does not know on the basis of that evidence that it is a goldfinch. Based on this sort of reasoning, the skeptic proposes the following plausible principle:

1.         A person knows that p on the basis of evidence E, only if E rules out alternative possibilities to p. 

Further support for this sort of principle comes from reflection on scientific enquiry.  Suppose that there are several competing hypotheses for explaining some phenomenon, and suppose that these various hypotheses are “live” in the sense that current evidence does not rule them out as possibilities.  It would seem that one cannot know that one of the hypotheses is true until further evidence rules out the remaining ones.  Again, principle (1) above looks plausible.
    The second step in the skeptical argument is to point out that there are various possibilities that are inconsistent with what we claim to know about the external world.  For example, it is possible that things appear to me visually just as they do now, but that I am actually lying in my bed asleep rather than sitting at my desk awake.  It is possible that things appear to Descartes’s just as they do, but that he is actually the victim of an evil demon, a disembodied spirit who only dreams that he inhabits a material world and is presently seated by the fire.  To be clear, it is no part of the skeptical argument that such alternative possibilities are true, or even that they are somewhat likely.  The point is only that they are possibilities, and so undermine our knowledge if our evidence does not rule them out. 
  The third step in the skeptical argument is to claim that our evidence does not in fact rule these possibilities out.  The gist of the present claim is something like this:  These possibilities are consistent with all the evidence that we have or could have at our disposal.  Even if, practically speaking, we don’t usually give such possibilities a thought, upon reflection we have no evidence available to us that counts against them, and in favor of our preferred beliefs.
  If we put these three claims together we have the materials for a powerful skeptical argument.  Here is the argument stated more formally.

(D)

1.    A person knows that p on the basis of evidence E, only if E rules out alternative possibilities to p.  (Principle 1 from above.)
2.    It is a possibility that I am not sitting at my desk awake, but merely dreaming that I am.
Therefore,
3.     I know that I am sitting at my desk only if my evidence rules out the possibility that I am merely dreaming. (1, 2)
4.    But my evidence does not rule out this possibility.
Therefore,
5.    I do not know that I am sitting at my desk. (3, 4)

And of course the skeptical argument is supposed to generalize. That is, it is supposed to apply to beliefs about the external world in general.  We therefore have:

6.    The same line of reasoning can be brought to bear against any belief about the external world.
    Therefore,
7.    No one knows anything about the external world.  (5, 6)

    One way to understand the notion of “ruling out” a possibility is as follows:  A body of evidence E rules out a possibility q if and only if E supports not-q in a non-circular way.  Here we can understand support as a semantic notion:  Evidence E supports propositions p, in the relevant sense, just in case E entails p or E makes p probable.  Putting these ideas together, we get the following interpretation of premise (4) of argument (D).

4a.  My evidence for my belief that I am sitting at my desk neither entails nor makes probable (in a non-circular way) the proposition that I am not dreaming.

    Why might one accept premise (4a)?  One reason for accepting (4a) is the considerations put forward by Hume’s argument above.  That is, one might think that my evidence for believing that I am sitting at my desk is the way things appear to me, together with my assumption that the way things appear to me is a reliable indication of the way things are.  But as Hume’s reasoning shows, there is no non-circular way to justify the assumption in question, and therefore no good evidence for either that assumption or further beliefs that are based on it.  In particular, my evidence cannot entail or even make probable (in a non-circular way) the proposition that I am not dreaming. Insofar as this is the reasoning behind (4a), argument (D) is parasitic on argument (H).
    There is, however, another way to understand the notion of evidence ruling out alternative possibilities.  On this understanding, a body of evidence E rules out alternative possibilities to p just in case E discriminates the state of affairs represented by p from alternative states of affairs.  For example, hearing my wife coming in the door from work, my auditory experience rules out the possibility that it is my children coming home from school or a burglar coming in through a window.  In effect, I have the capacity to “tell the difference,” so to speak, and this is what allows me to know that it is my wife who has just come in the house. On this understanding of “ruling out”, it does seem plausible that my evidence must rule out alternative possibilities in order to ground knowledge.  For example, how could I know that my wife has just come home, on the basis of hearing her come through the door, if I could not discriminate that state of affairs from my daughter’s coming through the door? Moreover, premise (4) of argument (D) becomes plausible on this understanding of “ruling out.”  We now have

4b.  My evidence does not discriminate my sitting at my desk from my merely dreaming that I am sitting at my desk.

One might think that this claim is obviously right.  To be clear-- I assume that the skeptical argument must be wrong somewhere.  My point here is that it isn't obvious where, or that the argument is invoking some very high standard for knowledge.

Comments (24)


Guest's picture

Guest

Sunday, March 25, 2007 -- 5:00 PM

Excellent synopsis. I think I agree with Professor

Excellent synopsis. I think I agree with Professor Taylor's post that the challenge of skepticism cannot be met, and so that our knowledge talk reduces to talk about belief formation strategies tailored to our phenomenal world.
Hume probably gave the only answer to the skeptical challenge one could hope to give, namely, that at the end of the day we all (do and probably should) set aside the assumptive and discriminative problems you've limned and go about "knowing" things about our world (such as it seems to us), with more or less fitting results. I might be trapped in a dream or a simulation, but then if so my best hope for escape would seem to lie in rational belief formation. For what other strategy is there?

Guest's picture

Guest

Sunday, March 25, 2007 -- 5:00 PM

The two skeptical arguments above are interesting,

The two skeptical arguments above are interesting, but I think Ken
was asking a question in his previous posts that has not
yet been addressed: are there powerful arguments
against rational (or justified or warranted) belief?
For instance, can we modify the above two arguments to produce
compelling arguments that no one can have justified beliefs about
the external world?
This had some plausibility:
H.4 Beliefs that depend for their evidence on an unjustifiable assumption do not count as knowledge.
but what about this?
H.4* Beliefs that depend for their evidence on an unjustifiable assumption do not count as justified.
A similar change for D is changing this
D.1 A person knows that p on the basis of evidence E, only if E rules out alternative possibilities to p.
to this:
D.1* A person is justified in believing that p on the basis of evidence E, only if E rules out alternative possibilities to p.
As far I can see, the reasons given in support of D.1 (on the second
sense of ruling out) support D.1* too. I am unsure about H.4*.

Guest's picture

Guest

Monday, March 26, 2007 -- 5:00 PM

Nice post, Patrick. I think here we need to make

Nice post, Patrick. I think here we need to make a distinction between epistemic and practical justification (this is relevant to Q's comment and Ken Taylor's post as well). I think there is a familiar sense in which an action A or belief B is practically rational if it is my best or only option. But then the skeptic is not challenging the practical rationality of either believing or acting on those beliefs. Rather, he/she is challenging the belief's epistemic standing, and claiming that it is not based on sufficiently good epistemic (truth-indicating) reasons. My point is now this, in favor of H.4*: I can see where it is sometimes practically rational to believe or act on the basis of epistemically unjustified assumptions. But it is much less plausible that one can be epistemically justified in believing on the basis of epistemically unjustified assumptions. If one can be, it should come as a big surprise.

MIke's picture

MIke

Monday, March 26, 2007 -- 5:00 PM

John, Doesn't the Humean argument depend on kn

John,
Doesn't the Humean argument depend on knowing a priori that, necessarily, it is possible that the way things appear are not the way they are? If that proposition is not necessary, then it is not knowable a priori (on Hume's view). But it certainly does not seem to express a 'relation of ideas'. On the other hand it is not a matter of fact, either.
But setting that aside, I guess I don't see why the epistemological standards are not high in this argument. To know, I'm required to rule out every deceptive/misleading alternative. That seems like a fairly high epistemic standard.

aaron's picture

aaron

Monday, March 26, 2007 -- 5:00 PM

The skeptical arguments are useless because they c

The skeptical arguments are useless because they cannot be met. A creative person can always come up with a reason why an answer isn't the only one - Hume's denial of reality could be the basis for refuting ANY question. There has to be context to the question, or it becomes meaningless.
Consider the desk argument. We assume the following:
1) dreaming is different from reality
2) I am an individual
3) when I use the word "sit", it means the same thing to me as it does to you
4) that I am not quantumly sitting at one desk, while standing in an alternate universe
Etc, etc. The skeptic can find an infinite number of reasons not to believe that a person sits at his desk. At its worst, this line of thinking becomes semantic, rather than philosophical.
The point of philosophy, I believe, is to ask questions that are in context, that have certain parameters that are mutually agreed upon. If two people cannot agree about the most basic of facts to begin a question, then the question loses all meaning.

Guest's picture

Guest

Tuesday, March 27, 2007 -- 5:00 PM

Mike, I don't think of the skeptical arguments

Mike,
I don't think of the skeptical arguments as making knowledge claims themselves. Rather, they take claims that look good to us and show us where they lead. So I am not sympathetic to replies of the form "The skeptical argument assumes we know . . ."
I think your comment about an implict high standard is right. Maybe it is wrong to say we have to rule out every alternative possibility in order to know. But now things get interesting. We would like a principled account of which possibilities need to be ruled out and which do not, and if we can give one I think we will learn something about the nature of knowledge in the process.
I have some ideas about what account to give here:
http://plato.stanford.edu/entries/epistemology-virtue/

Guest's picture

Guest

Tuesday, March 27, 2007 -- 5:00 PM

Aaron, I am not sure what your position is rega

Aaron,
I am not sure what your position is regarding the argument. You say it can't be answered, but why not? Because it makes no mistake? But then the conclusion that we lack knowledge is true. If you think we do have knowledge (as the result of context or whatever) then you must think that the argument goes wrong somewhere.
Some contextualists combine the importance of context with Mike's idea above: context determines which possibilities need to be ruled out and which do not. I tend to agree, but I think that backing this up requires us to say interesting and important things about what knowledge is and how it works. And if we can do that, then Hume's argument IS answerable.

MIke's picture

MIke

Tuesday, March 27, 2007 -- 5:00 PM

So I am not sympathetic to replies of the form

So I am not sympathetic to replies of the form "The skeptical argument assumes we know . . ."
Thanks John,
I'm very curious about this. In general, skeptical argument assert that "it is possible that (i) an evil demon is decieving you about x, or (ii) an evil scientist has you attached to a device that causes you to believe x, or..... That is, it seems plain that skeptical arguments assume some modal knowledge--some knowledge of what is possible.
Now suppose that no one advancing a skeptical argument claims that it is possible that I am being deceived/misled in any way. Suppose that they do not claim to have even that much modal knowledge. How do skeptical arguments not thereby lose their punch? If the skeptic does not know that it is possible that I am being decieved by a mad scientist, etc., then there is not much for the epistemic agent to be concerned about. In short, why would an agent have to rule out alternatives that are not known to be possible? I can't see any reason why they would. That's why I was urging that the skeptics must be claiming that they know, at least, that such an alternative is possible. And further, this is why I suggested that Hume (as far as I can see) would not be able to say exactly how we would know this.

Guest's picture

Guest

Tuesday, March 27, 2007 -- 5:00 PM

Mike, What makes the arguments interesting, on

Mike,
What makes the arguments interesting, on my view, is not that there is someone who is willing to defend them, and therefore someone who is committed to both the premises and conclusion. What makes them interesting, rather, is that the premises looks good to us, but we want to avoid the conclusion. This is a theoretical problem, not a practical or rhetorical problem, such as asserting something while at the same time denying the sort of knoweldge implied by the assertion.
Look at it this way-- the skeptical arguments would be interesting even if there were no one willing to assert them. We non-skeptics would still have exactly the same problem, i.e. that all the premises seem right whereas the conclusion seems wrong. We still want to know which premise to deny and why.

aaron's picture

aaron

Tuesday, March 27, 2007 -- 5:00 PM

John, My belief is that the ultimate skeptical

John,
My belief is that the ultimate skeptical position is a useless one, because it deflects any meaningful philosophical debate. I wholeheartedly agree that our knowledge is limited - we do not know for sure whether we only exist in one universe, or that we don't have a third hand in another dimension, or if moons beyond our galaxy are really made out of green cheese. But to have meaningful philosophical debate, there must be some common ground, some place to begin. We have to agree on the boundaries of the question, and that requires making assumptions.
Consider the woodpecker vs. goldfinch argument - one could argue they are different by pointing out the structure of the bones, provide DNA analysis, and any other number of scientific means of conclusively proving they are not the same. But then the skeptic says:
1) Your instruments might be faulty. All of them.
2) How do we know that the DNA for every woodpecker is different from the DNA of every goldfinch without testing them all?
3) Your samples are tainted with human DNA, due to handling...
Yes, those are all possibilities, but there is simply no end to them. There has to be a reachable probability, a place where we can say, "Based on this, I'm quite positive a goldfinch and a woodpecker are not the same." The true skeptic will never let you get there - if all else fails, he will whip out "reality isn't what it appears to be", and then you can't win no matter what you say.
At some point, to hope to argue any question, one has to assume some facts. Asking about the nature of reality is a separate question which defeats all others. That is the fatal flaw in Hume's argument - it is a good question, but not a good question upon which to challenge everything else. In order to move forward through the skeptical arguement, we would need to understand the true nature of reality. But if we did, the skeptic would then ask, "Do you truly understand the nature of reality? How do you know? Is it the only reality?" And then again we are faced with the semantic argument - if we have one, we can always linguistically have two.

MIke's picture

MIke

Tuesday, March 27, 2007 -- 5:00 PM

John, I think I see it. I was wondering how som

John,
I think I see it. I was wondering how someone (say, the skeptic, you or I) could reach the skeptical conclusion without assuming some modal knowledge. It does not seem possible. I guess we agree about that, right? Now two cases. Suppose I'm considering Unger's argument and so assuming Unger's epistemological standard's. If Unger is right, then I know that it is possible that all of my experience is being manipulated only if I am certain that it is possible that all of my experience is being manipulated, right? For Unger (I mean, the Unger of Ignorance) I know p iff. I am certain that p. Suppose that's right. In that case, I would know it's possible that p iff. I am certain that it is possible that p. But when it comes to such modal claims, there is not so much that I'm certain about. If certainty is required for knowledge, then I don't know that it is possible that all of my experience is being manipulated. The second case applies the same reasoning to Hume. So all I'm really suggesting is that we apply the epistemic standards that the skeptic insists on (whether or not I or you happen to find them reasonable)to the formulation of the skeptical challenge. The skeptical standards are right only if we don't know that there is skeptical challenge. It's basically an argument from self-defeat. Not persuasive?

Guest's picture

Guest

Wednesday, March 28, 2007 -- 5:00 PM

Does anyone have any philosophical sources that di

Does anyone have any philosophical sources that discuss the (obvious)first principle (that "A person knows that p on the basis of evidence E, only if E rules out alternative possibilities to p")? Cheers

Guest's picture

Guest

Wednesday, March 28, 2007 -- 5:00 PM

Aaron, You are imagining a debate with a commit

Aaron,
You are imagining a debate with a committed skeptic, and you realize that such a person can always raise questions about any claim that is made by his opponent in the debate. You also realize that such a conversation could get nowhere, so long as the skeptic remains consistent in his/her refusal to allow any claim. I entirely agree. If you ever meet such a person, by all means don't get into a conversation with him. But the skeptical arguments I am interested in don't ask questions, and nowhere do they depend on an assumption to the effect that no claims are admissable. So I don't see how your points address those arguments.

Guest's picture

Guest

Wednesday, March 28, 2007 -- 5:00 PM

Jeremy, I recommend the following: DeRose, K

Jeremy,
I recommend the following:
DeRose, K. and T. Warfield. Eds. (1999), Skepticism: A Contemporary Reader. New York: Oxford University Press. See especially DeRose's Introduction.
Pritchard, D. (2002a), ?Recent Work on Radical Skepticism.? American Philosophical Quarterly, vol. 39. no. 3, pp. 215-257.

Guest's picture

Guest

Wednesday, March 28, 2007 -- 5:00 PM

Mike, I don't find arguments from self-defeat p

Mike,
I don't find arguments from self-defeat persuasive here, partly for the reasons I have already given. But here is a different point: even if such arguments show that skeptical arguments are mistaken, they don?t show where they are mistaken. That is, they don?t show which assumptions of the arguments are false, and so no lesson is learned from them. Here is another thought: I am already assuming that the skeptical argument is mistaken somewhere. I think I know that I know that here is a hand, and so I don?t need self-defeat arguments to show me or convince me that the skeptical arguments go wrong. The interesting question is WHERE do they go wrong.
I think we can distinguish three grades of success in a response to a skeptical argument, each being more satisfying than the former: a) identify an assumption that we need not accept, b) find a reason for thinking that some assumption is false, and c) find an explanation for why some assumption is false, e.g. come up with a theory of knowledge that explains the mistake. Notice that an objection from self-defeat does not even give us the least satisfying of these grades.

aaron's picture

aaron

Thursday, March 29, 2007 -- 5:00 PM

John, I am directly addressing the second step

John,
I am directly addressing the second step of the skeptical argument, which you listed thusly:
"The second step in the skeptical argument is to point out that there are various possibilities that are inconsistent with what we claim to know about the external world. For example, it is possible that things appear to me visually just as they do now, but that I am actually lying in my bed asleep rather than sitting at my desk awake. It is possible that things appear to Descartes?s just as they do, but that he is actually the victim of an evil demon, a disembodied spirit who only dreams that he inhabits a material world and is presently seated by the fire. To be clear, it is no part of the skeptical argument that such alternative possibilities are true, or even that they are somewhat likely. The point is only that they are possibilities, and so undermine our knowledge if our evidence does not rule them out."
My point is simply that is impossible to rule out evil demons and such. It is the same as trying to prove a negative - proving that God does not exist, for example. The second step of the skeptical argument would clearly qualify as forcing us to prove a negative, would it not?

Guest's picture

Guest

Sunday, April 1, 2007 -- 5:00 PM

Aaron, But this sounds like you are simply agre

Aaron,
But this sounds like you are simply agreeing with the skeptic-- i.e. that there are various possbilities and they can't be ruled out. Maybe you are saying that they don't need to be ruled out for us to have knowledge.
On my view we have to get clear about what we mean by "rule out." On some readings, I think we can rule out the dream possibility, and so the premise is false. On other readings, I think it turns out false that we need to rule out all the alternative possibilities. But either way, there is something in the argument to deny, and progress to be made by explaining why we can challenge the argument at that point.

Guest's picture

Guest

Tuesday, April 3, 2007 -- 5:00 PM

Hello there, Interesting discussion. I want to

Hello there,
Interesting discussion. I want to make a proposal that might perhaps formulate better worries of people like Ken Taylor and others who have made similar points.
As well as justification of beliefs, we might perhaps define another quality: blameworthiness for believing something. (Just bear with me and it will make more sense at the end.)
Despite the moral connotations, the notion of blameworthiness I have here has nothing to do with blameworthiness in that sense. It's "epistemic blameworthiness" if I may so fancy. Suppose that a chess player, without due reflection and calculation, decides upon a move M. The chess player can be "blamed" for his belief that M should be his next move, since he decided upon it without any reflection.
Now suppose that one day you wake up and see a powerful demon who is laughing at all the foolish beliefs you just had and chastising you for not taking skepticism seriously. "But," you say, "there was no EVIDENCE whatsoever for believing in a skeptical hypothesis. True, I may not have had the correct beliefs. Nonetheless, given the evidence I had, these were the BEST beliefs that I could possibly have. Surely, I can't be BLAMED for having them." And this time, you wake up to find yourself in the Matrix.
My point is that even if the skeptic's arguments work for justification and knowledge, there is a sense of blameworthiness for believing that is substantially weaker than both justification and knowledge and for which the skeptics arguments don't work.

Guest's picture

Guest

Tuesday, April 3, 2007 -- 5:00 PM

Just an addendum. Here is the distinction betwe

Just an addendum.
Here is the distinction between justification and epistemic blameworthiness:
A weak chess player might contemplate over a chess position and after due reflection may decide on a move. The move may be indeed bad and in the light of proper analysis, completely UNJUSTIFIED. Nevertheless, the weak chess player can't be blamed for deciding on that, since he did his "epistemic duty".
I have a feeling that this discussion is likely to spill into the discussion concerning ethics of belief.

Guest's picture

Guest

Saturday, April 21, 2007 -- 5:00 PM

To strive above all at holding as many true and as

To strive above all at holding as many true and as few false beliefs as possible, is not rational. This is one of the valuable points made by Mikael Stenmark in a discussion with Vincent Brümmer about the theism-atheism debate.
Brümmer himself has often argued that since human beings are not merely knowing subjects, but rather actors, the rationality of their decisions as to which view of life to adopt, cannot be adequately judged from a purely epistemological point of view, but should take pragmatic considerations into account. In developing his argument, he draws on the work of Martin Heidegger, but a similar insight might also have been drawn from Ludwig Wittgenstein.
I fact, I think that Hume - unlike Descartes - was, in his own way, trying to make precisely this point when developing his sceptical arguments. He was not trying to convince anyone of scepticism, but rather illustrating the absurdity of a certain kind epistemological approach. The intelligent thing to do, the rational approach, is to get on with living in a way that works for one.
An important contemporary thinker who develops this approach to rationality quite extensively is Wentzel van Huyssteen. He views rationality from an evolutionary perspective, which helps him to see it as an adaptive capacity, something to be used in order to live meaningfully. This links up with perspectives in the philosophy of science that focus on the instrumental value scientific theories, the fact that they are intended to explain, predict and control.
From this kind of perspective the crucial question as far as our basic assumptions about the world is concerned, is not whether we can prove them, but rather whether it is wise to live with them, whether they help us to live well. And perhaps behind it all lies the intuition that if something works, that must be because it has some link with how things really are. And with the question: What does it mean for something to be "real"?
- Gerrit Brand
(Visit my blog at gerritbrand.blogspot.com)

Guest's picture

Guest

Tuesday, April 24, 2007 -- 5:00 PM

Hello! I hope no one minds me giving some opinion

Hello!
I hope no one minds me giving some opinions on this post.
I haven't read through every post above, but I would like to challenge this proposition.
1. A person knows that p on the basis of evidence E, only if E rules out alternative possibilities to p.
This seems ambiguous to me. Intuitively I should have thought if you recognise something, you recognise that thing. If your recognising that thing e.g. your wife consisted in ruling out other possibilities, that would seem highly implausible. How do you know which other possibilities are the ones you need to rule out? And why just these possibilities? On the other hand if you recognise your wife directly, then this as a matter of logic automatically does rule out all other possibilities because they are not your wife. So does this proposition 1) mean a) in order to recognise something (or have a reason for supposing something) this must entail some other possibilities are ruled out, or does it mean b) the nature of having evidence for E consists in ruling out other possibilities?
Even a) might be challenged. For instance it might be argued that if the only thing you ever saw you whole life was one shade of red, then that perceptual experience could never register in your consciousness. We must have at least one other visual experience so that we can contrast one thing with another to register either. This is an argument for a) and it seems plausible. But suppose you experienced just one degree of the most intense agonising pain all your life, does this mean that you could never even have any awareness that there was something wrong somewhere? And how would, or could you set about settling the matter beyond what may seem plausible in an argument?
Justin

Guest's picture

Guest

Sunday, March 15, 2009 -- 5:00 PM

An Equation of Truth Truth is when the subjecti

An Equation of Truth
Truth is when the subjective = the objective
Or simply: Subject = Object
Or more simply: =
= is truth.
Anything else is only probable or uncertain at best.
Life without measure is equal and equal makes the Universe One.
Equal = "free at last, free at last, free at last..."
"The truth shall set us free."
=
MJA

Guest's picture

Guest

Sunday, May 10, 2009 -- 5:00 PM

The old bottom line: Apply the skeptical argume

The old bottom line: Apply the skeptical argument to itself --- things could be another way entirely,we're brains in vats and so on ----and you will be skeptical of skepticism; things could be other than the way skeptics depict them. Skeptics, since they maintain that they know they are correct,cannot admit that things could be other than they say--without contradiction. If the reply is that one cannot apply skeptical argument to itself---why not?
The odd thing is that to make the skeptical argument work skeptics must hold,it seems that the world is a particular way and no other way--otherwise the skeptic could not hold that we cannot know the true state of things. Well the question arises---how does skepticism know there is a true state of things. Where do they get that?

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Guest

Sunday, May 10, 2009 -- 5:00 PM

If we'll never know if we know--have the correct

If we'll never know if we know--have the correct thought of-- the true state of things, then I could be wrong in holding that I don't
know the true state of things. But this seems intuitively impossible---how can I not know what thought
arises within me?

 

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