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Moegreche
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Moegreche
3,826 posts
Duke

So I was going to make this the next topic in the Great Debates, but I figured it might be more fun in a more open format. Before getting to the discussion point, I should make a few things clear.

First, radical scepticism shouldn't be viewed as an actual position that philosophers hold. Instead, it is part of the dialectic that any theory of knowledge should be able to address. So if I develop some particular theory of knowledge, one of the desiderata it should meet it to provide an answer to the sceptical challenge.

Second, the sceptical challenge asks whether (and to what extent) we have knowledge. This is not to say that the sceptic is claiming that we don't know anything - that would be ridiculous! Very, very few philosophers would doubt that we know things such as "Triangles have 3 sides" or "Bachelors are unmarried". Instead, the sceptical challenge is focused on knowledge of the world around us - what we might call empirical knowledge.

So here's the sceptical argument:

1) If I know that I have hands, then I know that I'm not a handless brain-in-a-vat.
2) I don't know that I'm not a handless brain-in-a-vat.
3) Therefore, I don't know that I have hands.

This argument can be generalised to encompass pretty much any claim about the world around us (e.g. that I'm sitting here typing and not just a brain-in-a-vat). Here's what that would look like:

1) If I know very much at all, then I know I'm not a BIV.
2) I don't know I'm not a BIV.
3) Therefore I don't know very much at all.

There are a number of ways to attack the above argument(s), which I would like to be the focus of this thread. Rather than throwing a bunch of jargon in here, I'll just see where this thing goes (if anywhere!).

One helpful hint when looking to attack an argument. The two most important questions you have in your philosophy toolbelt are: 1) 'Is the argument valid?', and 2) 'Is the argument sound?'. (Feel free to take a look at my Introduction to Logic thread for definitions of validity and soundness.)

So the basic question: How can we avoid the above conclusion of radical scepticism?

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FishPreferred
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FishPreferred
3,171 posts
Duke

Why would this need to be avoided? If what you refer to as knowledge is necessarily correct, this is the only rational thing to conclude.

partydevil
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partydevil
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Jester

1) If I know that I have hands, then I know that I'm not a handless brain-in-a-vat.
2) I don't know that I'm not a handless brain-in-a-vat.
3) Therefore, I don't know that I have hands.


it seems that 2) is always overruling 1), so then 3) is always contradicting with 1).
but what reasons are there for 2) to overrule 1)? cause 1) is a reason for 2) to be not true... you do know that your not a handless brain-in-a-vat.
(i dunno the expression "brain-in-a-vat". so i'm sorry if what i said is ridicules =P )
09philj
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09philj
2,825 posts
Jester

Where ignorance is bliss, 'tis folly to be wise.

- Thomas Gray
FishPreferred
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FishPreferred
3,171 posts
Duke

but what reasons are there for 2) to overrule 1)? cause 1) is a reason for 2) to be not true... you do know that your not a handless brain-in-a-vat.


This hinges on what you define as knowledge. "Knowing" that a conical cube cannot exist is not the same as "knowing" that Santa Clause cannot exist.

(i dunno the expression "brain-in-a-vat". so i'm sorry if what i said is ridicules =P )


It's a disembodied brain that is given fake sensory signals, making it believe it is a regular person, hypothetically.
09philj
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09philj
2,825 posts
Jester

As odd as it may sound, so what? You might as well make the best of your nonexistent life.


In any case, we have no idea how we would escape from it anyway. And it's better than being a brain in a vat. Also, who would want to wake up to a reality where they had been made to become a brain in a vat?
FishPreferred
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FishPreferred
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Duke

I honestly don't understand the significance of the "brain in a vat" argument.


It isn't about what you would do about it. The thought problem is only meant to explain how reality and perception can be altogether different.

By the way, Moegreche, the word is "skepticism."


Both spellings are correct. One is just more common.
09philj
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09philj
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Jester

[quote]By the way, Moegreche, the word is "skepticism."


Both spellings are correct. One is just more common.[/quote]

"Skepticism" is the US spelling. "Scepticism" is the UK and Commonwealth spelling. Moegreche is British. Thus, "Scepticism."
Moegreche
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Moegreche
3,826 posts
Duke

Why would this need to be avoided? If what you refer to as knowledge is necessarily correct, this is the only rational thing to conclude.


I was super careful to avoid referring to a particular conception of knowledge - but you're right in that the answer to the sceptical challenge will depend on one's definition of knowledge.
The main point, however, is that the conclusion (which apparently follows from highly plausible premises) is incredibly unintuitive. So if you want to claim that we lack knowledge, you'll have to give some story about this cognitive state we take to be knowledge.

but what reasons are there for 2) to overrule 1)? cause 1) is a reason for 2) to be not true... you do know that your not a handless brain-in-a-vat.


Excellent! So we could claim that (2) is just false - we do know we're not brains-in-vats! On a technical note, the BIV scenario is called a sceptical scenario or sceptical hypothesis. And your strategy is called a Moorean response to the problem (after G.E. Moore). The general thought here is that we can know the negation of the sceptical hypothesis.

So your argument would run like this:

1) If I know that I have hands, then I know I'm not a handless BIV.
2) I know that I have hands.
3) Therefore, I know that I'm not a handless BIV.

Any thoughts on this sort of response?

In other words, the conclusion is (insert name of fallacy). Take it or leave it. It's not my problem, and I can't force you to change your mind anyway.


We can't attack the conclusion of a valid argument - we must attack one of the premises. Now, there's definitely not a fallacy of composition going on here, but there might be something fishy going on with premise (1).
The point here is to work to show there's something wrong with the argument - not just suggest vaguely that there is.
But on your general point, there are lots of moves we can make against premise (1). But we'll need to give some sort of story as to why it's false.

So what?


Fair enough! But the things that you're talking about are practical in nature rather than epistemic. I was hoping to explain the 'so what' factor in the OP, but I guess it wasn't clear. The basic idea is that we must engage with the sceptical challenge in order to develop a satisfactory account of knowledge.

Here's another way way of putting it. The sceptical challenge is saying that we must know the negation of sceptical hypotheses in order to know very much at all. Some claim (including me) that we can know that sceptical hypotheses are false. Others claim we can't, but that (1) is false. These two different approaches lead to very different conceptions of knowledge!
MageGrayWolf
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MageGrayWolf
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Farmer

Knowledge of my hands existing can only be reference from the stimuli I'm receiving, whether that stimuli be the result of actual hands or a simulated construct being fed to a brain in a vat.

I suppose one way to describe what I'm saying is like this dream I had the other day. I was lying on my bed with my hands and arms across my chest. In the dream I heard a knock at the door and I could feel my left hand reach over and pick up a shirt next to me. At the same time I could also still feel my left hand lying across my chest. In the confines of that dream I had two superimposed left arm and hand. I can say that I know this, even though outside of that dream I don't.

MageGrayWolf
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MageGrayWolf
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Farmer

Just thought how I might be able to describe this a bit better.

Let's take Knowledge as justified true belief. Rather classic approach to it.
This about this is that true doesn't necessarily have to equate to real. Like in my dream it's true that I had two superimposed left arms, but that isn't real.

So it wouldn't matter if I really had hands or if my hands were just a product of a simulation being fed to me. It's still true within that stimuli. As such even if my hands are real or not the criteria for knowledge that I do can still be met, even if I was really a BIV.

Moegreche
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Moegreche
3,826 posts
Duke

This about this is that true doesn't necessarily have to equate to real. Like in my dream it's true that I had two superimposed left arms, but that isn't real.


So this a cool idea - we just mess with our theory of knowledge by adjusting the notion of truth. And this move makes sense. It's true to say that Harry Potter is a wizard, while it's false to say that he's rabid mongoose. But this only makes sense with respect to the Harry Potter world (i.e. the world described by the books). In the same way, we can say that P is true with respect to the world described by my perceptual experience.

So, here's a bad objection to this line:
Objection: If what's true is just what corresponds with my perceptual experience, then beliefs formed from visual hallucinations would still be true.

In other words, this objection is reading the view as if all there is to 'the world described by my perception' is just visual stimulation (i.e. what you're seeing). But it's more than that - it's even more that everything within your immediate experience. In fact, we could include many things that you believe and know (under this interpretation, of course). So things (like hallucinations) that don't cohere with your wider set of beliefs would be rejected as a belief in the first place - and thus they wouldn't even be in the market for knowledge ascriptions.

But there may be other, stronger objections to this view. Any thoughts?
MageGrayWolf
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MageGrayWolf
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Farmer

Objection: If what's true is just what corresponds with my perceptual experience, then beliefs formed from visual hallucinations would still be true.

In other words, this objection is reading the view as if all there is to 'the world described by my perception' is just visual stimulation (i.e. what you're seeing). But it's more than that - it's even more that everything within your immediate experience. In fact, we could include many things that you believe and know (under this interpretation, of course). So things (like hallucinations) that don't cohere with your wider set of beliefs would be rejected as a belief in the first place - and thus they wouldn't even be in the market for knowledge ascriptions.


There would be other means of gather perceptual information other than just visually that we could use to determine if what was being seen was real or not, for instance we could try and touch it. Relying on wider beliefs would also come into play in say, asking another person we already believe to be real if they see the hallucination.

With a hallucination we could still make true statements about it, even if we were to hold the false belief that the hallucination was real or even if we didn't.
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