Actually I think the key here is the collective nature of culture - is 'mimetic' the right word? We're immersed or embedded in the medium of language, culture and history, which is shared, in which we situate ourselves. Ergo, a 'collective consciousness'; the closer you go to the top level the more differentiated it is, but further down it merges with the archetypes and forms......

I have had similar experiences, when I was a teenager I became fascinated by dreams, I studied dream interpretation, tried to cultivate lucid dreaming etc. I didn't really get very far in learning to understand the process, I think because I was going through adolescence at the time and had a lot of emotional angst. What did happen though was that I began to dream more, at times it felt like living a week in dreams every night and I was getting short of sleep, so stopped and poured all my resources into drinking and partying at college.

In hindsight I can see how what I was dreaming about and the form of the dreams I was having were dictated by what was going through my head at the time and that age in my life, with a strong component of emotional anxiety.

So in reply I would say that although the dream state is experienced as quite real, it is entirely determined by, reflective of, your mental life and state in your body. Also it is entirely reliant on your brain activity for it to happen atall. If it were to be a true alternative reality as you speculate, it would require an equivalent hardware to produce the mental activity.

Although in principle I agree with you, in your speculation, which is partly why I was so fascinated by it myself in my youth.

To be clear, the argument from illusion concludes the existence of sense-data. But in its premise it is assumed that the appearance of the illusion somehow exists but not its object. Hence the conclusion that there must exist sense-data. But what appears in the case of an optical illusion is not the appearance of an absent object but some real effect of optics, such as refraction, or some real bundle of coloured shapes etc.. Those are examples of things we truly see in the case of optical illusions, but which we tend to mistake for something else. Without seeing real things there would be no illusions.

No, this just doesn't work. You're only shifting the goalposts – now we can just ask, how do I know whether everything I'm seeing isn't what I think it is, but merely a series of 'real effects of optics,' and whether I'm not perpetually mistaken about what it is I see, so that none of my perceptions are ever of the objects I take them to be?

And as to there being no illusions without veridical perceptions, I've already dealt with this above.

(Also, you aren't at liberty to assume that experiences are of external objects to begin with; nothing about having a certain visual impression implies the metaphysical conclusion that something external is causing this impression).

It's true that from experiencing and finding intelligible the differences between what we call 'reality' and 'dreaming' we can extraplolate to imagine that the reality might itself be a dream in relation to some other unknown reality. And sure there's no logical reason we can't keep extending that thought.

But this kind of imagining is parasitic upon our primary experience of the difference between reality and dream, the difgerence that we actually experience, and it is only in virtue of that experience that such imaginings are even posible and that the primary distinction between reality and dream exists and is intelligible.

It doesn't matter. The fact that this kind of imagining depends on a distinction noticed in experience doesn't mean that that distinction amounts to what we thought it did. We may simply be mistaken, and both waking and dreaming were part of a larger illusion, and we never had any veridical experiences. There is nothing incoherent about this.

What a realist says in claiming that our experiences are sometimes veridical is not that sometimes we have the experience of being awake. What they claim is that we really see objects as we think we do while having this experience. This claim isn't justified by the mere fact that we have two different sorts of experiences, and frpm this take one of them to be evidence for a certain metaphysical thesis. It's a bad argument, it doesn't work. If you want to defend realism, find a better one.

The distinction is one that is significantly more than merely "noticed". The distinction is fundamental to the intelligibility of our experience taken as a whole. Dreaming is not a shared experience; whereas what we call reality is an inter-subjectively shared and agreed upon experience.

I have not made any claims about independently existing "objects" at all, so I don't know where your objection about a supposed metaphysical claim you apparently think I am making is aimed. That said, it is true that in everyday discourse public objects are taken to be independently existent simply by virtue of the fact that that is the only really coherent way we can think about and account for their being experienced in common. Of course there may be some deep connection of minds that explains the commonalities of experience; but even then the objects that are reliably persistent and available to perception in common would count as being, even if only in a merely logical sense, independently real. And really what other coherent sense is there in which to think about it?

As to the logical possibility that reality taken as a whole might be radically different than we imagine it to be; sure, it's logically possible. the problem is that when we are asked to imagine a possible scenario in which that might be true we cannot but imagine the hidden real reality in exactly the same familiar terms as our familiar reality. So, the idea doesn't have much currency really because we cannot turn it into any coherent story that does not consist in elements taken from the reality we are familiar with. In other words such an idea is really inconsequential; it is as nothing to us, because it must remain a difference that could make no possible difference on account of the fact that we cannot even begin to frame it as a real difference.

Dreaming is not a shared experience; whereas what we call reality is an inter-subjectively shared and agreed upon experience. — John

What is experienced is the beetle in the box. All we know for sure is that we use the same words to describe what we see and hear and feel and whatnot.

But, of course, this assumes that we're not dreaming; that the reality we experience now and the people in it aren't just figments of our own imagination.

As to the logical possibility that reality taken as a whole might be radically different than we imagine it to be; sure, it's logically possible. the problem is that when we are asked to imagine a possible scenario in which that might be true we cannot but imagine the hidden real reality in exactly the same familiar terms as our familiar reality. So, the idea doesn't have much currency really because we cannot turn it into any coherent story that does not consist in elements taken from the reality we are familiar with. In other words such an idea is really inconsequential; it is as nothing to us, because it must remain a difference that could make no possible difference on account of the fact that we cannot even begin to frame it as a real difference.

We don't have a problem understanding that our TV screen is just a collection of individual lights that when activated a certain way is seen by us as a scene full of people and things. The individual lights and the things we see are very different. It's not hard to apply this principle to everyday life, where things like atoms stand in for the individual lights.

We know we use the same words and we know that others identify the same features of objects as we do. That's why se say things are independently, because things are reliably experienced in the same ways by most everyone.

That the TV screen is either "just a collection of individual lights" or " a scene full of people and things" or anything else we can imagine or come to think it is or might be; none of this is a case of reality being radically different than we imagine it to be. The fact is that we simply cannot genuinely think of reality as being radically different than we imagine it to be, and that is the point that makes the merely logical possibility that it might be radically different than we imagine it to be really quite an empty incoherent idea.

We know we use the same words and we know that others identify the same features of objects as we do. That's why se say things are independently, because things are reliably experienced in the same ways by most everyone. — John

That's an invalid inference. You can't go from "we both say that we see a red car" to "we're both having the same kind of experience". It might be that what I call "red" you call "orange" and what I call "orange" you call "red" (imagine Locke's inverted spectrum hypothesis). So we might both see the car differently; we just describe what we see using the same words.

That the TV screen is either "just a collection of individual lights" or " a scene full of people and things" or anything else we can imagine or come to think it is or might be; none of this is a case of reality being radically different than we imagine it to be. The fact is that we simply cannot genuinely think of reality as being radically different than we imagine it to be, and that is the point that makes the merely logical possibility that it might be radically different than we imagine it to be really quite an empty incoherent idea.

The TV screen being a collection of lights is radically different to there being a bunch of people fighting zombies. The reality of the TV screen is radically different to what we see.

And the reality of our everyday world as described by physicists is radically different to what we see.

It's not only coherent; it's already readily apparent.

Entirely incoherent. If the world is different, my experience aren't illusionary-- I still experience a tree in front of my house-- there's simply more to the world. Not an inaccuracy in what I experience, but a fact there's is something else I haven't realised: a world outside my experiences.

In the difference between "real" and a "dream," it is not the possibility are experiences are mistaken which defines the distinction, but the world outside experience. For us to even have dreams, there must be more of the world, the "real" states, outside our experience.

If you place a hundred people in front of a red car and a green car and ask them to identify each they will reliably do so. The fact that due to physical constitution or whatever people may see things slightly differently doesn't change the fact that things are generally reliably seen in much the same way by most everybody.

If reality were truly radically different, it would be unrecognizable, unintelligible. We cannot even imagine such a scenario, so it is effectively meaningless. The 'real' reality is always 'brains in vats' or 'mad scientists" or "demons" in other words constructed out of familiar elements taken from the reality we do experience. Our imaginations have access to no other material.

The fact that due to physical constitution or whatever people may see things slightly differently doesn't change the fact that things are generally reliably seen in much the same way by most everybody. — John

You have no evidence of this. All you know is that they use the same words to describe what they see. What they actually see is the beetle in the box.

If reality were truly radically different, it would be unrecognizable, unintelligible. We cannot even imagine such a scenario, so it is effectively meaningless.

We don't need to be able to understand what reality is "really" like for reality to be radically different to what we see. So it's not clear what you're trying to say here.

But even then, it's not a given that the "reality" of reality is unintelligible. Perhaps the world as described by quantum mechanics is accurate (and presumably intelligible to physicists). So we know what reality is "really" like and know that it is radically different to our everyday experiences.

We have no proof, and that is what you are really, inappropriately demanding. But we do have good evidence, insofar as we have little reason to doubt, since there simply is not any competing explanation for why people do routinely see the same things. How ofetn have you pointed at a car for example and said 'look at that car' and the other person said' that's not a car, it's a dog'? Or even 'that's not a Maserati, that's a Volkswagen beetle'. ;Let's go into that coffee shop':'that's not a coffee shop that's a swimming pool'. "I'm going to take you to the mountains tomorrow"; "this isn't the mountains: it's the opera".

But we do have good evidence, insofar as we have little reason to doubt, since there simply is not any competing explanation for why people do routinely see the same things. — John

You're begging the question. We don't know that people routinely see the same things. We only know that people routinely use the same words to describe what they see.

How ofetn have you pointed at a car for example and said 'look at that car' and the other person said' that's not a car, it's a dog'? Or even 'that's not a Maserati, that's a Volkswagen beetle'. ;Let's go into that coffee shop':'that's not a coffee shop that's a swimming pool'. "I'm going to take you to the mountains tomorrow"; "this isn't the mountains: it's the opera".

This is a false analogy. I'm saying that we might use the same words to describe different things. It's the beetle in the box example given by Wittgenstein. We both use the words "car" and "opera" and "coffee" in the same public situations but the private what-it-is-like aspect of our experiences might be radically different.

If reality were truly radically different, it would be unrecognizable, unintelligible. We cannot even imagine such a scenario, so it is effectively meaningless. The 'real' reality is always 'brains in vats' or 'mad scientists" or "demons" in other words constructed out of familiar elements taken from the reality we do experience. Our imaginations have access to no other material.

I actually largely agree with your position, but I don't render the unknown reality as unrecognisable, unintelligible, or effectively meaningless. This is principly for two reasons; that it can be considered as an undescribed necessary being, in terms of its necessary roles in our known reality. Also that it is possible for our imaginations to access other material through both creative activity and revelation. Such revelation can be accessed through dreams to which I can testify myself.

This is a false analogy. I'm saying that we might use the same words to describe different things. The above is an example of people using different words. — Michael

The fact that we don't use such different words shows that we experience the same things. If you are going to say things such as that what I experience as having a cup of coffee, someone else might experience as what I would call 'swimming the length of an Olympic pool' then I am just going to say, "don't be silly", and leave the conversation there. I'm really not much interested in these kinds of conversations, and only get sucked in usually because it pains me to see people saying silly stuff.

If you are going to say things such as that what I experience as having a cup of coffee, someone else might experience as what I would call 'swimming the length of an Olympic pool' then I am just going to say, "don't be silly", and leave the conversation there. — John

But that's not what I'm saying. I'm only saying that the way they experience coffee might be nothing like the way you experience coffee.

The fact that we don't use such different words shows that we experience the same things. — John

No, it doesn't. It only shows that we've been taught to use the same words in the same public situations. We were put in front of an apple and told that its colour is "red". Now we use the word "red" to describe whatever colour we see the apple to be; and we might see radically different colours.

Yes, I think that if there is an underlying spiritual reality that manifest as our familiar physical reality, then we must have the intuitive or clairvoyant capacities to see that, or at least the ability to develop them. I haven't been able to do that thus far, but I remain fully open to the idea. And I believe that the way we would see that reality must be in terms familiar enough that they would not be incomprehensible to us, or we would be able to see nothing.

we've been taught to use the same words in the same public situations — Michael

How could we be taught to use the same words in the same situations if we could not recognize them as such?

Sure, but they still experience coffee, not swimming pool.

how do I know whether everything I'm seeing isn't what I think it is — The Great Whatever

Obviously not by continuing to assume representational perception; basically your question and problem arises from that asumption, i.e. that you only see your own impressions, sense-data or the like, and never the objects directly.

I don't make that assumption.

nothing about having a certain visual impression implies the metaphysical conclusion that something external is causing this impression). — The Great Whatever

Whence the assumption that it would be an impression? See, you continuously assume representational perception without noticing it .

Obviously not by continuing to assume representational perception; basically your question and problem arises from that asumption, i.e. that you only see your own impressions, sense-data or the like, and never the objects directly. — jkop

Nope. Even if, like you, we assume that all perception is without a representational intermediary, you still have to come up with an explanation for hallucination, claiming that it's a real perception not of sense-data, but of a misleading ocular phenomenon, or something like that. But then we just have the same problem, rewritten without sense data: how do we know that all of our perceptions are not just of these misleading ocular phenomena and not of what we think they are?

No sense data required, and their removal does nothing to help you.

Whence the assumption that it would be an impression? See, you continuously assume representational perception without noticing it . — jkop

Fine – having a visual experience in no way leads to the metaphysical conclusion that something external causes it.

But that's not what I'm saying. I'm only saying that the way they experience coffee might be nothing like the way you experience coffee. — Michael

This assumes that people experience the same coffee, just in different ways. It's common knowledge that that happens.

how do we know that all of our perceptions are not just of these misleading ocular phenomena and not of what we think they are? — The Great Whatever

I mistakenly thought you were supporting the Argument from Illusion, but you aren't. That argument begins by pointing out that we are sometimes mistaken (which obviously implies that some of our assertions are true.) You're just arguing that global skepticism can't be defeated. That's true.

That argument begins by pointing out that we are sometimes mistaken (which obviously implies that some of our assertions are true.) — Mongrel

Why would that be?

Because it's a positive assertion. We are sometimes mistaken. The only way that could be known is if we have access to the truth.

If the initial premise was that we might be mistaken, then no access to truth would be necessary.

If one person tells me that there are two balls in the bag and another person tells me that there are three balls in the bag then I know that at least one of them is wrong even though I don't know which (if either) is correct. And if I first see two balls in the bag and then see three balls in the bag then I know that at least one of my experiences is mistaken even though I don't know which (if either) is correct.

Inconsistency is all that is required to recognize that we are mistaken; we don't need to know/see the truth.

The number of balls could be changing from moment to moment (the balls are really alien spaceships and they go into hyper-space as needed.) So both people could be right. If you're going to embrace global skepticism, contiguity past to future is out the window.

I don't think the argument from illusion even has anything to do with the OP. It's just a mistake I made about what TGW was saying.