Thursday, March 06, 2014

Does Skepticism Destroy Its Own Empirical Grounds?

You might think that empirically grounded radical skepticism is self-defeating.

Consider dream skepticism. Suppose I have, or think I have, empirical grounds for believing that dreams and waking life are difficult to tell apart. On those grounds, I think that my experience now, which I'd taken to be waking experience, might actually be dream experience. But if I might now be dreaming, then my current opinions (or seeming opinions) about the past all become suspect. I no longer have good grounds for thinking that dreams and waking life are difficult to tell apart. Boom!

(That was supposed to be the sound of a skeptical argument imploding.)

Stephen Maitzen has recently been advancing an argument of roughly that sort: that the skeptic "must attribute to us justified empirical beliefs of the very kind the argument must deny us" (p. 30). Similarly, G.E. Moore, in "Certainty", argues that dream skeptics assume that they know that dreams have occurred, and that if one is dreaming one does not know that dreams have occurred. (Boom.)

One problem with this self-defeat objection to dream skepticism is that it assumes that the skeptic is committed to saying she is justified in thinking (or knows) that this might well be a dream. The most radical skeptics (e.g., Sextus), might not be committed to this.

A more moderate skeptic (like my 1% skeptic) can't escape the argument that way, but another way is available. And that is to concede that whatever degree of credence she was initially inclined to assign to the possibility that she is dreaming, on the basis of her assumed empirical evidence and memories of the past, she probably should tweak that credence somewhat to take into account the fact that she can no longer be highly confident about the provenance of that seeming empirical evidence. But unless she somehow discovers new grounds for thinking that it's impossible or hugely unlikely that she is dreaming, this is only partial undercutting -- not grounds for 100% confidence that she is not dreaming. She can still maintain reasonable doubt: Previously she was very confident that she knew that dreams and waking life were hard to tell apart; now she could see going either way on that question.

Consider this case as an analogy. I have a very vivid and realistic seeming-memory of having been told ten minutes ago, by a powerful demon, that in five minutes this demon would flip a coin. If it comes up heads, she will give me a 50% mix of true and false memories about the half hour before and after the coin flip, including about that very conversation; if tails, she won't tamper with my memory. Then she'll walk away and leave me in my office.

Should I trust my seeming-memories of the past half hour, including of that conversation? If I trust those memories, that gives me reason not to trust them. If I don't trust those memories, well that seems hardly less skeptical. Either way, I'm left with substantial doubt. The doubt undercuts its own grounds to some extent, yes, but it doesn't seem epistemically justified to react to that self-undercutting by purging all doubt and resting in perfect confidence that my memories of that conversation are entirely veridical.

This is the heart of the empirical skeptic's dilemma: Either I confidently take my experience at face value or I don't. If I don't confidently take my experience at face value, I am already a skeptic. If I do confidently take my experience at face value, then I discover empirical reasons not to take it confidently at face value after all. Those reasons partly undercut themselves, but that partial undercutting does not then justify shifting back to high confidence as though there were no such grounds for doubt.

(image source)


schmaltz said...

Hello Eric, How can you judge experience, or mis-judge experience, if all you can do is experience that situation? In your example, when this powerful demon might change your memory, does that change the fact that your experiences will still be fully experienced by you? I don't think so. This also proves the dream question. What is the level of experience that you experiance things? That would tell you whether you are dreaming or not.

Eric Schwitzgebel said...

Thanks for the comment, schmaltz! I grant (for this argument) that you know what your experience is like "from the inside" as it were; the question is what causes the experience -- an external reality with features like those represented in the experience, or instead your dreaming brain?

Tim said...

I totally agree with the substance of your reply, but I have a couple of, I hope, not completely irrelevant remarks.

(1) Maitzen’s objection, it seems, is similar, but also different in interesting ways from Peter Kung’s objection (in his “On the Possibility of Skeptical Scenarios”, European Journal of Philosophy). While Maitzen argues that the sceptic must concede empirical knowledge if the sceptical scenario is supposed to more than a mere possibility, Kung argues that she must concede that even if she’s contend with presenting a mere metaphysical possibility. Kung’s version of the objection is more interesting, or so it seems, because it doesn’t presuppose that sceptics want to or should present more than a mere possibility.

(2) Maitzen argues that we can’t know that dreams or illusions/hallucinations occurred without having *empirical* knowledge. One argument is that we can’t just find out introspectively that our experiences are inconsistent and infer that one of them must be an illusion. I don’t get that argument and I’m interested in reading what you think about it. A counterexample are experiences of cross-modal inconsistency. For example, the stick in the water appears to be both straight (haptically) and not straight (visually). So contrary to Maitzen I can know *introspectively* that illusions occur. Or am I missing something here?

(3) In your example may I confidently believe that *if no demon tampers with my memory*, the janitor inspected the lawn instead of believing that the janitor inspected the lawn? I’m asking because hedging is often a good response to empirical undercutters but good sceptical arguments must be immune to hedging, that is, I can’t answer the sceptical challenge by simply adding "unless I’m a biv" to every empirical belief.

Steve Maitzen said...


(1) I hadn't heard of Kung's paper. Thanks for citing it. Judging from a quick glance at it, Kung's argument seems to depend on rather detailed claims about the epistemology of modality. But those claims may be right. I'll have to read it carefully.

(2) I don't think that the tactile and visual impressions in your example are a priori inconsistent. We learn only a posteriori that sticks that look a particular way to our eyes typically feel a particular way to our hands. For all we can know a priori, sticks half-immersed in water "feel straight" even when they're crooked -- or perhaps just this particular stick, when half-immersed in water, feels straight even though it's crooked. (We can't know a priori that all sticks behave the same way.)

Callan S. said...

Eric, I think that's more like skepticism running into unquestioned assumptions - ie, the unquestion assumption that there is 'awake' and that there is 'dreaming'.

Skepticism has to blow up when it runs into things that are just taken to be true and will not be questioned any further - it's like a car crashing into a wall in slow motion. It doesn't show something new about the car, but instead something about the wall.

Howard Berman said...

Is the classical skeptical argument that we might be dreaming the same as the argument that there is no real difference between dreaming and waking consciousness?
From a Kantian perspective you might put forth this claim; or maybe the real world just doesn't exist

Marco Devillers said...

I agree somewhere with Callan that it seems difficult to completely discriminate between dreaming and awake states of being.

Not sure you can lift that into a philosophical argument though.

Eric Schwitzgebel said...

Tim, thanks for those very thoughtful comments and the tip on the Kung! I do think that the Kung and the Maitzen have some commonalities. One difference is Kung's focus on metaphysical possibility. I'm inclined to think that epistemic possibility is the more important target, but perhaps I could be convinced otherwise with more argument.

I don't have a lot invested in whether we could know a priori that illusions exist. Steve has replied, as you see, and maybe that reply works. I think it's a little hard to know what counts as "a priori", and my own skeptical concerns are empirically motivated anyway -- so I'm happy to concede him that point at least for the sake of argument.

I agree that the hedging response is open, and also that it's not really a satisfying response to the skeptic -- but with one caveat: as with certain other hedges (like ceteris paribus conditions on scientific laws), it might not be possible to non-circularly specific the full content of the hedge.

Eric Schwitzgebel said...

Callan: I don't know. I kind of think that the skeptic's discovering her own hidden assumptions can actually feed her own skepticism: Wow, I knew even less than I thought! What else might I soon find out that calls even more of my assumptions into question?

Eric Schwitzgebel said...

Howard: I don't think indiscriminability at the moment implies lack of difference, though. There might be an indiscriminable difference, or the states might be discriminable in retrospect.

Eric Schwitzgebel said...

Marco: see last year's post defending dream skepticism!

Eric Schwitzgebel said...

Marco: see last year's post defending dream skepticism!

Marco Devillers said...

I read it. But you still seem to make a sharp distinction between being awake or dreaming.

What about dreamingly turning your alarm off or zoning out while you're watching TV?

The point is to make the distinction vague, not to apply credence to a sharp distinction.

But again, I have no idea whether that translates to a philosophical noteworthy argument.

schmaltz said...

Hello Eric, I don't doubt what you replied but I don't see the distinction. Picture this: I stub my foot hard on the table leg. There is a mark on the wood and my leg is throbbing. At that moment, according to you, its possible to tell between a dream-scape and an experiential movement. But an hour later, according to your position there is much less of a chance, or no chance, that you kicked the table. The reality of the damaged table is as claim-able as anyone else who experienced a table, and has memories of stubbing their feet. This is all in-sync with the experiential totality.

Callan S. said...

Eric, true I'd say, but I'm not sure it's cracked emperical grounds - possibly more cracked what we claim are emperical states, ie awake and sleeping.

Eric Schwitzgebel said...

Marco: Interesting thought about challenging the sharp distinction. Maybe early-morning confusion can blur that distinction. But you're right for the most part I'm assuming a sharp distinction.

Schmaltz: I'm not sure I understand your position here. Sorry!

Callan: If I'm getting you, I think I agree. If this is a dream, then that does call into question my assumption that there is a clear distinction, of the sort I'm inclined to think that there is, between dreams and waking. This is part of Maitzen's and Moore's point. And yet calling it into question is perfectly compatible with skepticism.

Callan S. said...

Eric: I think it depends on what the practice of emperical skepticism is - is it to take on the notion maybe there is a hard, emperical measure on the matter - but it's a matter of speculation where it lies (some might speculate its here, some speculate it's there)no ones fixed to one position for it. Or is the practice one where folk are fixed to one position for the emperic measure? Certainly the latter seems to head right for the self defeat you describe. But what about the former - maybe it warrants a different name for taking it that matters will reach an emperic measure at some point (but without being dogmatic on where that point is)?

Carrie Kay said...

I often have memories in third person p.o.v. My dreams are like that too.

Marco Devillers said...

Yeah well. I developed periods of mental confusion over the years; partly due to the fact that they don't know how to treat that but that's another story.

Given that I am now a bit of an expert on the subject I really doubt people have any idea how deluded their image of the world is.

I am willing to claim that everyone's awake experiences is a perception of the world through a dream-like filter. Which begs the question what one exactly means by being awake. Ultra-skeptically, that's an argument that consciousness doesn't even exist.

Ah well. Maybe you can use the arguments somewhere.

LessWrong said...

I respectfully disagree with your conclusion.

As a starting point, we might ask "How can we trust our memory?". That is a completely fair question, and there are plenty of ways to verify it empirically. We might do a very simple test like writing something down on paper, then attempting to write it again after some time by memory. Comparing those two papers would show that your memory works. On an intuitive level, we do already know that memory works though. Every time you open the kitchen cupboard to find exactly what you expected, it's evidence that you remembered what was in it. If you had no memory, you wouldn't be able to predict the contents in advance. So trusting our memories is a good default position, and here's exactly why I don't think your argument proves anything substantial: in your scenario, you required evidence to start doubting. It would be bad skepticism to trust your memories when you have evidence you shouldn't! Not confidently taking your memories of a memory altering demon at face value is the only sensible thing to do, and doesn't undercut empirical skepticism when the whole reason you doubt is evidence. Those two options you listed sound distinct on a superficial level, but what are they really saying? If you don't confidently take your experience at face value, good. You have evidence why you shouldn't. If you do confidently take your experience at face value, then you think about it and discover empirical reasons to not take it seriously hopefully you'll change your mind. Both options lead down the same path. Your empirical evidence is your memory of the conversation, whether or not you can trust the memory to be accurate the true evidence is that your memory exists. Either you had the conversation, or something already is altering your memories to make you think you did. Either way what you did was excersize empirical skepticism, not undercut it. You definitely shouldn't trust your memories in that kind of situation, it's an answerable question.

The same thing goes for your dream scenario. Where does your belief "It's difficult to tell whether I'm awake or dreaming" stem from? You argue that if you're dreaming, your observations from the past are suspect but the bigger point is that you don't need them at all. Finding yourself in a situation in which it's hard to tell whether you're awake or dreaming -is- good grounds for believing it's hard to tell whether you're awake or dreaming. I don't see the contridiction that causes skeptical arguments to implode. Even if you did find yourself in a situation where you have to mark some of your previous evidence as suspect, you don't just throw empirical skepticism out the window. A good empirical skeptic would start running tests to determine whether they were awake or dreaming. Try finding distinguishing evidence like whether or not a clock tells the same time when you look at it, look away and then look back again. I don't see anything in your argument that shows the method itself is flawed.

Eric Schwitzgebel said...

LessWrong: Thanks for the thoughtful comments. I think we might be on the same side of these issues, though. I also don't think that the skeptical arguments implode.

LessWrong said...

I'm a bit confused. From your comment:

"(That was supposed to be the sound of a skeptical argument imploding.)"

Eric Schwitzgebel said...

At that point I was speaking in the voice of my opponent. Sorry if I wasn't clear enough about that in the post!