Answering the Skeptic

I need to also be able to recognize them for what they are, but according to the skeptic we can't.

I think it is very reasonable to think that having evidence in favor of something simply consists in a. having in some sense a cognitive "access" to the evidence (and notice that in your example this requirement isn't met since you cannot read French, while in the perceptual case you can directly perceive your environment without further ado) and b. the evidence itself should in some sense guarantee the truth of what it is evidence for (and this requirement is met when you are having a waking experience, since in that case your cognitive state is very reliably correlated with the facts that you perceive).

1. For any p, if a subject doesn’t have evidence which rule out (perhaps conclusively) the possibility of an error regarding p (that is, favor the possibility that p over not-p), then the subject doesn’t know that p.

2. Waking experience is indistinguishable from a very vivid dream (or a deception by an evil demon, or being a brain in a vat etc. – insert here your favorite skeptical scenario), since there are no distinct "marks" to distinguish the one from the other.

3. Therefore, for every p a subject can’t have evidence that favor p over not-p (from (2)).

4. Therefore, no p can be known (from (1) and (3)).

Then let's change my example slightly. I am given a piece of paper that either has random symbols drawn onto it or Arabic writing. In either case I have cognitive "access" to the evidence; I can see it right in front of me. But I don't know if it's random symbols or Arabic writing. I need some second order understanding of how to distinguish the two. And with the case at hand, I need some second order understanding of how to distinguish a veridical and a non-veridical experience, which the skeptic claims we do not have.

In this case what you need is simply to know Arabic (or at least being able to reliably identify Arabic writing). And this is not "second order" evidence in my sense, because for you to know that you know (say) Arabic, all you need is simply the mere ability to read Arabic, and you don't need in addition some further ability to identify your own fluency in Arabic which is distinct from you just being fluent in the language.

So knowing Arabic requires more than just being presented with Arabic words. Somehow I need to learn that these symbols are in fact Arabic words. And so knowing that our experiences are veridical requires more than just being presented with veridical experiences. Somehow I need to learn that these experiences are in fact veridical.

But, again, at best your argument is "if our experiences are veridical then we can know that our experiences are veridical", but given that the skeptic questions the antecedent, your argument would seem to beg the question. I could even turn your argument around and argue that because our experiences are not veridical we know that there isn't an external world (or at least none that we see).

But my point is that knowing that something is an Arabic script is inseparable from the ability to understand Arabic (that is, you cannot describe someone as being fluent in Arabic without presupposing that he can as a matter of fact read Arabic); and analogously, knowing that you are having a veridical experience is nothing but just having it as a matter of fact.

You know that you are seeing a tree just by seeing a tree (and perhaps some other conditions like the absence of fake tree facades in the vicinity, re the Gettier problem)

This is why I called it a "version" of his argument, and my aim wasn't to correctly represent his actual philosophical views. And in any case, my argument does show that we can (in some sense) acquire certainty about the world, since being in a waking state does actually logically entail that you cannot be in error about what you perceive.

Hence the skeptic cannot for his argument presuppose at the same time the conceptual distinction between waking and dreaming states, and also treat them as if they were the same.

Fafner:the way things appear to you when you are awake usually matches very closely the way they really are....

You're not comparing like for like here. Simply having a veridical experience is comparable to simply being shown an Arabic word. Just as the latter isn't the same as understanding Arabic, the former isn't the same as knowing that the experience is veridical.

To offer another example, let's say that I'm shown a painting, which may or may not be a forgery. You seem to be suggesting that if it's the real painting then I know that it's the real painting, or if it's the forgery then I know that it's the forgery. But that's just not right. The fact that it is or isn't the real painting isn't sufficient to claim knowledge that it is or isn't the real painting. And so the fact that it is or isn't a veridical experience isn't sufficient to claim knowledge that it is or isn't a veridical experience.

Fafner:the way things appear to you when you are awake usually matches very closely the way they really are....

But the sceptic will say that this simply begs the question, i.e. assumes what it sets out to prove. If one's life were a perfectly well-ordered and consistent dream state, then the correlation between experience and the objects of perception could likewise be perfectly consistent and empirically verifiable. Even if fundamental physical constants were actually part of an illusion, provided they were consistent, then they would still make accurate predictions.

The difference is this: a non expert cannot visually distinguish forgeries from non-forgeries, while we all can in most cases distinguish trees from non-trees.

But we can't distinguish between a veridical experience of a tree and a non-veridical experience of a tree (or so the sceptic claims), and so the analogy holds.

I just don't know if right now I'm being deceived by an evil demon.

And you can make that distinction on the basis of the nature and quality of experience - that the experience of waking and dreaming is qualitatively different.

The whole point is that there is no subjective differences between waking and dreaming states, otherwise, how appeal to dreams supposed to prove skepticism?

As I then desired to give my attention solely to the search after truth, I thought … I ought to reject as absolutely false all opinions in regard to which I could suppose the least ground for doubt, in order to ascertain whether after that there remained [anything at all] in my belief that was wholly indubitable. Accordingly, seeing that our senses sometimes deceive us, I was willing to suppose that there existed nothing really such as they presented to us … [T]he very same thoughts (presentations) which we experience when awake may also be experienced when we are asleep, while there is at that time not one of them true, I supposed that all the objects (presentations) that had ever entered into my mind when awake, had in them no more truth than the illusions of my dreams. But immediately upon this I observed that, whilst I thus wished to think that all was false, it was absolutely necessary that I, who thus thought, should be somewhat; and as I observed that this truth, I think, therefore I am (cogito ergo sum), was so certain and of such evidence that no ground of doubt, however extravagant, could be alleged by the sceptics capable of shaking it. 1

Mere inability to distinguish on subjective grounds all non-veridical states from veridical proves absolutely nothing about ones knowledge of the world. Again look at the original argument

There's no mention of waking and dreaming states, simply the observation that things appear real to us in dreams, yet are not, so, likewise, the reality of things that appear to our senses may be doubted. This is what leads directly to the famous declaration cogito, ergo sum.

The problem I see is that it is still feasible that the waking state, the state of presumed normality, is still a consistent illusion. It would be logically possible that, at the time of death, one is suddenly roused as if from a sleep, to a mode of existence that one had never guessed at while alive, but which now is obvious once again; one might immediately begin to forget the life you had just lived, in the same way as forgetting dreams that you have just had woken from.

I've already addressed it. It's epistemic luck, not knowledge. Unless you can distinguish between a veridical and a non-veridical experience (or between a real painting and a forgery) then you can't know that your experiences are veridical (or if the painting is real).

Sure, it's logically possible that life - by analogy - has the structure of a dream, but we really have no reason to suppose so (at least in our ordinary consciousness). Lacking a reason to suppose so means that doubting it would be irrational. Much more, within the waking state we come to know about the distinction between awake and dreaming, hence if even being awake is dreaming, then we have destroyed the notion of awake - and hence the notion of dreaming, which also depends on the notion of being awake. Language is rendered meaningless by such skepticism.

This is just pedantry. You can always accept the meaningful distinction between wakefulness (experiences of an external world) and dreaming (experiences not of an external world) but claim that those experiences which we claim to be of wakefulness aren't actually so.

So you cannot know that my belief that I see a tree is merely lucky if you don't know whether in fact there is a tree in front of me (and perhaps also whether my ability to detect trees in general is genuinely reliable). But of course the skeptic doesn't claim to know that there are in fact no trees (if he wished to prove that my believe is merely lucky), so it would be of little help to appeal to epistemic luck on his behalf.

No you can't. Meanings are developed based on experience. If you categories the experience of being awake as being equivalent to the experience of dreaming, then the meaning of awake and dreaming collapses.

They're not equivalent. They're different. But neither are experiences of an external world.

If the meaning of awake no longer has a reference in experience, then that meaning has been destroyed. If you say that being awake is dreaming, then you have short-circuited your language.

The claim is that if the experience isn't veridical then your belief is false and that if your experience is veridical then your belief is just lucky. So the sceptic doesn't need to claim that there are or aren't any trees. He just argues that either way there isn't knowledge.

To be able to get beyond luck to actual knowledge you must somehow know that your experience is veridical, which according to the sceptic isn't possible.

or they can claim that they are defined as being the experience of an external and imaginary world respectively, in which case both types of experience fall under the umbrella term "dreaming" (even though they have other properties to distinguish them).

But how is skeptic supposed to prove that if my experience is veridical then it is lucky? I'm not quite sure what you mean by "luck" here, but at least in the literature it means roughly something like basing your belief on an epistemic policy which doesn't reliably track the truth. But what makes a policy reliable is its relation to the environment in which is is exercised, so that means that you must know some facts about the world in order to assess whether my perceptually based beliefs are reliable. If my capacity to visually distinguish trees from non-trees (in the environment in which I in fact live) is reliable, then my beliefs which I form on the basis of experience cannot be lucky when true - and the mere possibility the this very same policy could misled me in some other worlds in which there are no trees is irrelevant to the question whether by believes are lucky.

How does it follow? Surely being awake doesn't fall under the umbrella of "dreaming" because it isn't...

Agustino:Sure, it's logically possible that life - by analogy - has the structure of a dream, but we really have no reason to suppose so (at least in our ordinary consciousness). Lacking a reason to suppose so means that doubting it would be irrational.

So the possibility that one's understanding is fundamentally delusional or deeply mistaken about the nature of reality should always be considered. Indeed I think that was the original impulse behind sceptical arguments.

Otherwise we'd always be doubting ourselves,

But given that I can't distinguish between the real painting and the forgery, in the case that my belief is true I'm just lucky.

I said that if "dreaming" is defined as being of an imaginary world, and if the experiences which we claim to be waking experiences are actually of an imaginary world, then those experiences aren't actually waking experiences but dreams.

But claiming something to be a waking experience is a different matter from it actually being a waking experience, so what you are describing is not an example of a waking experience that "falls under the umbrella of "dreaming" ", but just a plain instance of dreaming.

because what does it mean to be awake if not to be in a state which is logically inconsistent with having a dream?

And what does it mean to being able to 'distinguish' between the two?

To be able to determine if I'm having a veridical experience or a non-veridical experience.

And what does it mean to "determine"?

Being in a state that is logically inconsistent with being asleep and dreaming does not imply that one can distinguish the two states, because the inconsistency does not stem from the difference in the mental state but from the fact whether one is awake or asleep.

To recognise some feature that veridical experiences have and non-veridical experiences don't.

Being in a state that is logically inconsistent with being asleep and dreaming does not imply there is perceptual evidence of being in any state, because the inconsistency does not stem from the difference in the mental state or perceived reality but from the fact whether one is awake or asleep.

But if this is the case, then contra the skeptic, being in the one state as opposed to the other does after all entail information about how the external world actually is, because the way things appear to you when you are awake usually matches very closely the way they really are – something which is plainly not the case (at least most of the time) when one is dreaming.

And how does it logically prove that I don't know that I'm having a veridical experience from the fact that I can't recognize such a feature?

Being in a state that is logically inconsistent with being asleep and dreaming does not imply there is perceptual evidence of being in any state,

There is a hypothetical scenario where the other state does not entail that information, of which you'd be completely unaware of because it's your only source of how the things are.

And how does it logically prove that I don't know that I'm having a veridical experience from the fact that I can't recognize such a feature? — Fafner

If you can't recognize it, how do you claim you know it?

And how does it logically prove that I don't know that I'm having a veridical experience from the fact that I can't recognize such features?

You seem to be conflating. I'll set it out more clearly.

1. We have experiences of type A and experiences of type B.
2. We refer to experiences of type A as "wakefulness" and experiences of type B as "dreaming".
3. We claim that wakefulness is the experience of an external world and that dreaming is the experience of an imaginary world.

There are two ways for the sceptic to approach this. They can either claim that "wakefulness" and "dreaming" are defined by their referents, in which case our claim that wakefulness is the experience of an external world is false, or they can claim that they are defined as being the experience of an external and imaginary world respectively, in which case both types of experience fall under the umbrella term "dreaming" (even though they have other properties to distinguish them).

Nothing about this "destroys meaning" or "short circuits" language.

But again, this is just pedantry. The sceptic's claim is simply that we can't know that our experiences are of an external world, regardless of what we call them or think of them. You can't counter this by pointing to a dictionary.

it merely says that it's enough if you just have the right sort of evidence, but doesn't mention recognition. You have to add a further premise here.

I don't think I'm conflating anything.

If experiences of type A are actually "dreaming" as well, then what grounds our concept of wakefulness?

of Gods

or demons

unicorns

We don't need to have had an experience of an external world to have the concept of an experience of an external world.

Yes we do need to have had an experience of exteriority - something external to us - in order to ground the concept of external world

So I must have seen a ghost because I have the concept of ghosts? That's wrong. I have the concept, but I've never seen one.

What's your concept of a ghost?

Its atomic concepts, you have had an experience of all of them.

So I've had the experience of a disembodied thing?

Furthermore, at best your argument can only have you conclude that at some point you've had an external world experience.

Yes. By disembodied you refer to things like light - light has no body (according to your own beliefs in the other thread). Think about what you imagine when you imagine a ghost.

Then you'd need to specify that point and also why you think your experience was of an external world then, and not now.

Except I don't imagine ghosts to be electromagnetic radiation. I imagine them to be non-physical things.

How are ghosts shown in paintings, etc. ? Be honest with yourself. You can't imagine a non-physical thing. What you really mean by non-physical in this context is something that has a shape, but can go through walls, etc. that kinda stuff.

The concept of an external world doesn't come from experience at all, but from rational consideration.

Yes it does. You experience things like your thoughts and emotions, and you see that they're not always the same. But you wake up in the same bed (presumably). Because of its constancy, you deem one to be independent of your experience - it looks the same every time you come back to it - while the other - like dreaming, your mind, etc. you view it as depending on your experience. This concept arises precisely out of experience - more specifically the experience of the constancy of the external world, and the impossibility of altering it just by thinking about it.

But simply having a veridical experience isn't evidence that it's a veridical experience, just as simply having the real painting isn't evidence that it's the real painting.

The evidence must allow you to rule out the possibility that you're wrong, and for that you need to recognise some distinguishing feature, as with the painting.

Now if having a waking experience defined as a state such that things necessarily match the way they appear to me, then if I'm having a waking experience I'm in a state which entails the presence of whatever that I perceive

The trick here is in treating "waking experience" and "dreaming experience" as two different kinds of state, and this distinction is epistemically relevant because having a waking experience is by its very nature to perceive reliably how things are in the world, which is not the case with dreams.

There's no reason to assume that whenever I know something, then I must be able to recognize all possible cases of deception or illusion.

A brain in a vat would also come to the same conclusion to explain the consistency of his experiences, despite the fact that none of his experiences are of an external world.

If you are in a waking state your experience is strongly correlated with how things are in your environment (otherwise it would not be a waking experience by definition), and hence it is correct to regard your perceptual states as good evidence.

And thus the idea is that the inability to distinguish some hypothetical cases of dreaming from waking, doesn't prove that we can never distinguish dreaming from waking, since in a straightforward sense we often can do just that.

But how do you know how things are? You can't know that, you can only ever know how they appear to you.

How so? If you are not, then it's possible that case of deception or illusion is true, and so you can't be sure things are how you think they're instead of you being deceived, ie. you don't know for sure.

Sure, but the brain in the vat has no grounds to doubt that his experience is of an external world (and in some sense it is, because the electrical impulses stimulating his brain do come from an external world).

He's just saying that we can't (or don't) know that it isn't.

Knowledge is that which we have when we don't have grounds for doubt. Knowledge can change and evolve.

So you equate knowledge with certainty (in the sense of conviction).

I might not have any grounds to doubt my girlfriend's faithfulness, but that doesn't mean that I know she hasn't cheated on me.

Yes it does. Until further evidence, you know she hasn't cheated on you. You cannot rationally doubt her faithfulness if you have no reason to.

For one, I can only know that she hasn't cheated on me if she hasn't cheated on me. Knowledge requires truth, not just no reason to doubt. But then as Gettier showed, truth and justification are not sufficient either.

Well, if you have evidence that entails that things are the way the they seem, then I think it's very plausible to call it knowledge.

But what if cases of illusion or deception are not actually possible, given the state the I'm right now in? (i.e., of not dreaming but being awake)

Surely my not being able to recognize all cases of dreaming, don't prove that I'm actually dreaming right now!

Simply having an accurate report isn't evidence that the report is accurate, and simply having veridical experiences isn't evidence that the experiences are veridical.

Far better to just stick with "experience of an external world" and "experience of an imaginary world". So the sceptical hypothesis is that we can't (or just don't) know if our experiences are of an external world or an imaginary world, and more strongly that the experiences that we ordinarily consider to be of an external world are actually of an imaginary world.

Well yes, having an accurate report doesn't prove by itself that your report is accurate

And from the fact that you don't have some independent checks for the reliability of your report it doesn't follow that it is epistemically imprudent or irresponsible to rely on a report which looks to be a reliable report as far as one can tell

First, what even is this evidence you could have of things being as they seem? Second, knowledge in this context means 100% certain with absolutely no possibility of it being false in any hypothetical or theoretical situations, no matter how inplausible. So no, unless you can distinguish any deception or illusion, the claim is not palusible.

No, but that's not the point. It proves that it's a possibility, even if the odds of that are one in infinity, and that there's no absolute proof of you being awake.

So having a veridical experience doesn't prove that the experience is veridical. And the sceptic's claim is that we can't know that our experiences are veridical.

So in this case we have some means to test the accuracy of the report. We can check to see if things are as the report says. But what can we do to test the veridicality of an experience? How do we check to see if our experiences correspond to some external world? This is where we need to be able to recognise some feature that veridical experiences have and non-veridical experiences don't.

The fundamental problem with the notion of an external world experience is that it places the very thing that defines it as being an external world experience outside the experience. The brain in a vat has no way of knowing if his simulated world is an accurate representation of the external world.

I don't agree that the external world is "outside" our experience.

The skeptic can claim this, but as I said many times, it doesn't follow from this that we cannot know anything about the external world.

Surely the relevant question to ask whether I know that something is a cat is whether what I see appears as a cat - and the question whether I'm dreaming or something like that, has nothing to do with it.

I don't agree that the external world is "outside" our experience. And surely you have to know first whether there is actually an external world, in order to know whether it is outside our experience, don't you think?

You've phrased this very ambiguously. Let's say I meet a woman and that, unbeknown to me, she's your mother. In one sense it is correct to say that I know your mother, but in another sense it's wrong to say that I know that she's your mother.

The sceptic is saying something about the latter sort of knowledge. I can't know that the experience I'm having is an experience of an external world.

It has everything to do with that. The sceptical hypothesis is that we can't know that we're not brains in a vat, for example. No amount of examining cats is going to help us answer that. Unless there's some known feature that "real" cats have and simulated cats don't.

I think that's just true by definition. We say that some object is "external" if it exists when not being experienced.

Again, you are just assuming here that knowing that p requires the ability to detect every conceivable possibility of p being false, while I saying that such an assumption is unwarranted. Again, there's no much that I can add to what I already said on this point.

How can you claim that knowing that p consists of anything other than excluding the possibility that p is false? If you can know that p, without excluding the possibility that p is false, then what does "knowing that" amount to?

So my point is this - when you know that p, then your evidence must objectively entail the truth of p

I didn't actually deny what you said that I denied (that knowing p means ruling out p's falsehood) - and I agree with you on this. I only disputed the claim that knowing must also entail being able to detect (from the subjects point of view) all cases of p's falsehood, and I think this is something else.

What must rule out the possibility of falsehood is your objective evidence. So for example, if you are in a waking state perceiving a tree in full daylight, you cannot possibly be in this very same state and still be wrong about the tree.

So my point is this - when you know that p, then your evidence must objectively entail the truth of p -

Your approach seems to just be the truism that if the belief is true then it cannot be false.

But that's not what I'm saying. Compare the case of believing that there's a tree outside because you seem to see that there's a tree outside, and just guessing correctly that there's a tree outside. In the first case you are basing your belief on a capacity that within certain parameters (that is, in the right sort of environment) is an extremely reliable tree-detector (meaning it can detect real trees as opposed to fake trees, but not real trees as opposed to extremely vivid hallucinations). While in the second case of guessing you are not exercising any such a capacity, but merely depending on pure chance. But if you are exercising your tree detecting capacity in the right sort of environment, then it's not a matter of chance that you seem to see a tree whenever there are real trees (and not seeing trees when they are none), so there's an important difference between relying on perceptual experience, and merely guessing correctly

In my example I see your blond mother, but I still don't know that your mother is blond. It's not enough that I exercise a reliable detecting capacity in the right sort of environment. I need periphery understanding (in this case, that the person I see is your mother).

In the first case you are basing your belief on a capacity that within certain parameters (that is, in the right sort of environment) is an extremely reliable tree-detector (meaning it can detect real trees as opposed to fake trees, but not real trees as opposed to extremely vivid hallucinations).

I didn't say that having this sort of capacity is sufficient for knowledge, that's a different question. Obviously you have to be responsive in the right sort of way to the deliverances of you perception - I agree that not all instances of e.g. directly seeing a tree (de re) are instances of knowledge, but I don't see the relevancy here.

The relevance is that simply having a veridical experience isn't enough to claim that one has knowledge of the external world. You need the periphery understanding that your experience is veridical, but that kind of understanding is impossible (according to the sceptic).

Again, we've been over this already. I don't know what you mean by "knowing that your experience is veridical". As it stands it just means nothing, and so it is no objection.

If you don't know that the tree you see is an external world tree then you don't know that there's an external world tree, even if the tree you see is an external world tree. Just as if I don't know that the blond woman I see is your mother then I don't know that your mother is blond, even if the blond woman I see is your mother.

It means knowing that the tree you see isn't just in your head. That you're not dreaming or imagining or a brain in a vat or being deceived by an evil demon.

You just repeated the world "know" here, but I asked what are the relevant requirements (according to the skeptic) for knowing such a thing?

Recognising some evidence as ruling out the possibility that you're wrong, as per your opening post. If I can't recognise some evidence as ruling out the possibility that the tree I see is just in my head – that I'm a brain in a vat or being deceived by an evil demon – then I don't know that the tree I see isn't just in my head.

You have to distinguish between two senses of recognizing your evidence: a. knowing that if you have evidence of type E then you cannot be a brain in a vat and b. infallibly knowing that you indeed have evidence E and not merely seeming to have them. I agree that knowing (a) is necessary for knowledge, but not knowing (b).

I know that if I have evidence that you have a sibling then you cannot be an only child. That doesn't mean that I know that you're not an only child. I need to actually have such evidence and recognise it for what it is. If I meet your brother but don't know that he's your brother then I don't know that you're not an only child.

Your conditional account of knowledge doesn't work. You need to actually have such evidence and recognise it for what it is. The problem is in recognising the evidence for what it is. How you do recognise that the experience you have is evidence that you're not a brain in a vat? The sceptic claims we can't.

I don't see how you can make this conclusion. A person in a waking state may have poor eyes, poor judgement, or be hallucinating when thinking that they are in a state of perceiving a tree.

You seem to be neglecting the fact that evidence must be judged. The person must judge the perceptual evidence, as well as the meaning of the statement "that is a tree", in order to know that that is a tree. Human judgements can be mistaken. Therefore the person can be wrong.

So here you use "objectively entail" to refer to the judgement which must be made. How do you ensure that the human judgement is not mistaken?

I meant to exclude such cases, of course there are many ceteris paribus conditions that we must take into account. I meant that when you perceive a tree (you are not dreaming, your eyesight is normal etc.) then your perceptual state is correlated with the fact that there's a tree in front of you, and this is an objective matter. This is what should be properly regarded as your evidence.

No, it doesn't refer to my judgment. You know that p, if you judge that p on a basis of evidence which entails that p (and p is true). Such judgments are fallible as you say, but it doesn't show that they are not knowledge when they do succeeded.

My point, is that the evidence, your perception of a tree, never provides the basis for a conclusion which beyond the possibility of doubt. If you exclude all the cases in which you were wrong, i.e. it turned out to be a shrub or something like that and not a tree, to support your claim that the judgement is beyond doubt, then you are being unrealistic.

Since "knowledge" as you use it refers to a successful judgement, and you have no way of knowing whether your judgement is successful or not, because you acknowledge that your judgement is fallible, then you have no way of knowing whether your judgements are knowledge or not. Therefore you should doubt all your knowledge.

If we just stop being obsessive about absolute certainty, and adopt some more modest standards for knowledge claims (which is not the same as not having standards at all), then there will remain no longer any good reason to worry about what the skeptic is saying, and thus no reason to not to be confident in most of our claims to know.

The underlined portion of the quote is exactly what the (philosophical) skeptic is saying: that there is no absolute certainty, knowledge, or truth that we can apprehend, only optimal approximations of absolute certainty, absolute knowledge, or absolute truth - which is not the same as not having standards at all.

No, he doesn't say that - rather he's saying that there's no such thing as knowledge of the external world as such.

To found my statements in fact, both Plato and Hume held that there is an external world. Both were staunch philosophical skeptics, rather than parodies of what philosophical skepticism entails.

It depends on what one means here by "evidence". On my understanding, having evidence for p is being in a state of such kind that you cannot be in this very same state when p is false.

The skeptic says that our confidence in all of our claims to knowledge ought to be 0, since there are some crazy possibilities of error that we cannot rule out. But does it follow? I think not.

Now, suppose that you form a belief that there's a tree in front of you on the basis of your experience. Is your belief entirely without grounds as the skeptic claims?

I don't think so, because the experience that you are having does rule out objectively, some possibilities of error - e.g., that you are looking at a traffic light or a painting of a tree etc.- since it is impossible for a person with a normal eyesight and proper lighting conditions to take a painting or a traffic light for a real tree.

So in pother words, what I'm trying to argue is that we have good grounds to trust our judgments (and take them to be knowledge) even in the face of their fallibility, since it is simply not the case that they are completely groundless. Why should we assess our judgments relative to the imaginary stories that the skeptic tells us? If we just stop being obsessive about absolute certainty, and adopt some more modest standards for knowledge claims (which is not the same as not having standards at all), then there will remain no longer any good reason to worry about what the skeptic is saying, and thus no reason to not to be confident in most of our claims to know.

See the conclusion of the skeptical argument in my first post.

That's a ridiculous definition of "evidence". Evidence supports a belief it does not render it impossible that the belief is false. That's why to convince someone of something it usually requires more than one piece of evidence. If evidence for a belief rendered the belief necessarily true, then all that would be required would be one piece of flimsy evidence and the belief would necessarily be true.

I think you misunderstand skepticism. The skeptic doesn't claim that our confidence ought to be zero, the skeptic claims that the confidence cannot be one hundred percent. And, since we cannot have absolute, one hundred percent confidence in any claim of knowledge, all knowledge ought to be doubted.

Again, I think you misrepresent skepticism. The skeptic does not think that the belief is entirely without grounds, the skeptic thinks that the grounds for the belief ought to be examined.

But very often people mistake shrubs for trees, and trees for shrubs. It is a common mistake. A small tree might be mistook for a shrub, and a shrub might be mistook for a small tree. How do you rule out this possibility for error unless you know that the person is adept in this type of judgement?

Skepticism is not a claim that knowledge is "completely groundless". It is the claim that the grounds are just as likely to be mistaken as anything else is.

What would be the point in lowering the standards for knowledge? You seem to think that this would get rid of the skeptic, but actually the reverse is true. If the standards are lowered, we can say P is knowledge when we have a lower degree of certainty of P. This means more cases of what is called knowledge turning out to be false, giving us more reason to be skeptical of anything which is called knowledge.

The argument concludes "no p can be known". It defines "know" as ruling out the possibility of error, in premise 1. The argument says nothing about degrees of confidence in one's belief. The skeptic doesn't say, as you claim, that we can have zero confidence, the skeptic says that if "knowing" requires ruling out the possibility of error, as per premise 1, then we cannot know anything. This does not say that we cannot have any confidence in our beliefs. It says something about the nature of "knowing".

What is crucial is that for something to be 'evidence' it must be intimately correlated with the facts that it is evidence for.

If your grounds for claiming that you know something don't justify you to say that you know, then I think it comes down to the same thing as saying that you don't have any good reasons at all to say that you know (and hence you ought not to have any confidence in your knowledge whatsoever).

The structure of the skeptical argument is such that all of your claims to knowledge are completely worthless unless you've ruled out all possibilities of error.

Obviously the skeptics' argument is based on the idea that you can't say that you know something unless you are not absolutely sure that you are not mistaken - and of course this is the assumption that I'm rejecting.

No, evidence is apprehended as being correlated with the belief which it is evidence for. So you have two things wrong here. First, the thing which the evidence is evidence of, is a belief it is not a fact. It cannot be called a fact, because the purpose of evidence is to convince someone of something which may or may not be true. Second, in order for it to be called evidence, it need not be intimately related to the belief, it needs only to be perceived as such. This is what makes it evidence of the thing, the fact that it is perceived as being related to the thing, whether or not it actually is, is irrelevant.

No, evidence is apprehended as being correlated with the belief which it is evidence for. So you have two things wrong here. First, the thing which the evidence is evidence of, is a belief it is not a fact. It cannot be called a fact, because the purpose of evidence is to convince someone of something which may or may not be true. Second, in order for it to be called evidence, it need not be intimately related to the belief, it needs only to be perceived as such. This is what makes it evidence of the thing, the fact that it is perceived as being related to the thing, whether or not it actually is, is irrelevant.

This doesn't make any sense to me. You seem to be using "justify" in a strange way. We often claim to know something when someone we trust has told us that. But this is not at all a form of justification. So we often claim to know something, and have a reason for making such a claim, yet that reason doesn't constitute justification.

I've already told you, as well as javra has told you, that this is a misrepresentation of skepticism. In my last post, I clearly pointed out, in your own argument, how what you say here is not true to your argument.

The argument, as you presented it, is that if knowing something requires absolute certainty, then we do not know anything. It does not say that you cannot know anything unless you are absolutely certain.

2. Waking experience is indistinguishable from a very vivid dream (or a deception by an evil demon, or being a brain in a vat etc. – insert here your favorite skeptical scenario), since there are no distinct "marks" to distinguish the one from the other.

It only begs-the-question if you believe that propositions like "I live on the earth" or "I am a person," need some kind of justification

At some point it just doesn't make sense to epistemically doubt that there is no difference between, for example, dreams and waking states.

There is something very fundamental about our perceptions that's generally grounded for us, i.e., we generally accept them as veridical without the need for justification.

Does one's working definitions of Waking and Dreaming reduce to immediate empirical contents, to non-immediate empirical implications, to both or to neither?

Do the sets of experiences referred to by one's working definition of waking and dreaming overlap, or do waking and dreaming refer to disjoint sets of experiences?

But what I mean by an 'internal limit' is simply to say that (trivially) what is thinkable is limited by what is thinkable, and by "thinkable" I don't mean merely a psychological phenomenon, but the limits which are set by our concepts or logic, which define what makes sense to us.

But what I am saying is that what reality is (in the strong metaphysical sense of 'things-being-in-themselve-independently-of-our-minds') is precisely that thing which we imagine ourselves to know if indeed we know it and are not mistaken

Yes, we do, but it doesn't follow from that that we're right. You're welcome to just commit to this acceptance and carry on with your life, but that hardly counts as a good philosophical defence of the position against alternatives (anti-realism, idealism, phenomenalism, etc.).

We have the same position here, i meant empirical verification only in the internal sense of methodological solipsism - as opposed to epistemological solipsism. In other words what is not cognizable in terms of first-person experiential phenomena is judged to be meaningless and lacking truth-value as opposed to being transcendentally right or wrong but unknowable.

Unfortunately "mistakes" and "knowledge" in ordinary language are usually interpreted in terms of Truth-By-Correspondence, and this commonly held background assumption in conjunction with your "if" clause makes your paragraph read as if you at least concede to the dream-sceptic that the dream/reality distinction is logically conceivable in terms of T-B-C.

In other words, Truth-by-correspondence about everything as a whole is neither right or wrong, but meaningless because it is unthinkable, so that neither skepticism nor non-skepticism in this sense is strictly meaningful. Isn't that the case?

As i previously suggested, i suspect that some dream skeptics, possibly most of them, are implicitly defining the "dream vs reality" distinction in terms of the coherence and cohesiveness of their experiences - which is of course an entirely internal notion to experience that is both understandable and doesn't involve any Cartesian notion of transcendental truth-bearers beyond the individual's experience.