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From: jeff@aiai.ed.ac.uk (Jeff Dalton)
Subject: Re: When is a simulation of a Y a Y? (Was Bag the Turing
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Date: Wed, 25 Jan 1995 19:15:05 GMT
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In article <D2xL96.AMB@spss.com> markrose@spss.com (Mark Rosenfelder) writes:
>In article <D2pzFL.L38@cogsci.ed.ac.uk>,
>Jeff Dalton <jeff@aiai.ed.ac.uk> wrote:
>>>>In article <D2D0sM.55o@spss.com> markrose@spss.com (Mark Rosenfelder) writes:
>>>>>The fact that we are not aware of everything outside the fovea being a blur
>>>>>does *not* show that we have a "detailed internal representation".  Dennett
>>>>>shows (in _Consciousness Explained_) that the notion that the brain fills
>>>>>in some detailed picture of what the eyes see, even neatly airbrushing over
>>>>>the blind spot, is a fantasy, a relic of the Cartesian Theater.
>>>>
>>>>Does Dennett show (a) that anyone interesting actually holds the view
>>>>that the brain fills in or (b) that this view _is_ a relic of the
>>>>Cartesian Theatre?
>>
>>I've returned to this point in the thread because I've just gone back
>>and read the sections of _Consciousness Explained_ that deal with
>>blind spots and "filled in".  So this is about Dennett and blind
>>spots.  I don't say anything about "everything outside the fovea being
>>a blur", though I suppose similar considerations might apply.
>>
>>[...] I do not agree that (a) Dennett shows that anyone holds the
>>view of "filling in" that he criticizes or (b) that Dennett has shown
>>this is a relic of the Cartesian Theater.  Nor has he shown that they
>>use scare quotes because they're embarrassed.  His claim that Hardin
>>can't "bring himself to say" plaid is filled in is unsupported.
>
>You're reading Dennett here over-literally, just as you accuse him of
>doing below.  

It's a common problem in comp.ai.phil, and I never thought I was
immume to it.  Also, it's possible you're reading me too literally as
well (when concluding that I'm talking about proof in (presumably)
some strong sense of proof).

>Of course he hasn't *proven* that Hardin "can't bring himself
>to say" plaid. 

I'm not asking him to *prove* it; but "show" I didn't mean prove,
and I'd accept much less than proof.  But why _does_ Dennett think
this is what's going on?  What evidence does he give?

Note that I used "show" from the start.  You did not object to "show"
when arguing that the answers to my (a) and (b) were both "yes".
(Indeed, "show" was introduced by you, if I haven't gotten the
articles mixed up.)

> How could one prove such a thing anyway?  Dennett is pointing
>out that Hardin describes filling in the blind spot with blue, but not with 
>plaid.  He finds this suggestive, and I do too: it seems a stronger claim
>that the brain has some kind of filling-in process for plaid.  So we have
>some skepticism about a plaid filling-in process; Dennett then invites us
>to apply this same skepticism to any kind of filling in of the blind spot.

All we're actually shown by Dennett is that Hardin *didn't say*
fill-in for plaid.  For all Dennett's shown, it was just an accidental
syntactic variation.

>>Let me present a quote from a recent net article (by Andrzej Pindor):
>>
>> [...]
>>
>>To me, at least, this "filled-in" is a perfectly reasonable way
>>to talk and doesn't owe anything to Cartesian Theatres.  So I offer
>>it as an example.  It's possible to say "filled-in" without getting
>>into trouble.
>
>Certainly we know things about the world even with our eyes closed;
>but we still find it useful to keep them open, even in our own bedrooms
>with nothing changing.  So Andrzej's remarks do not show that the brain 
>fills in details that the eyes do not see (because of the blind spot or the
>lower resolution outside the fovea); on the contrary, with our eyes closed
>we have an even lower information content than non-foveal vision offers.

Note that I did not say Andrzej's remarks showed anything of the sort.
I'm just suggesting (by example) that the mere use of phrases such as
"filled-in" doesn't show very much, even though Dennett seems to think
such phrases go with Cartesian Theatre thinking.

It's really necessary to read what Dennett says.  I invite people to
do this and see if they can explain what view Dennett things Hardin
et al hold and why he thinks they hold it.  So far as I can tell,
neither of these things are very clear (to say the least).

>>But what about those other guys, Hardin at al?  When someone talks
>>about "filling-in" part of the visual field, it can sound rather
>>like they have in mind an observer looking at something projected
>>on a screen.  But it seems to me that all they're really saying is
>>that we don't notice the blind spots  [...]
>
>Then why don't they say that?

I suspect they do, at some point, say we don't notice blind sports
(or something along those lines).  But why should they avoid saying
"filling-in"?  At one point, Dennett talks of areas already being
labeled plaid (or maybe blue).  That sounds at least as questionable
as "filled-in" to me.  Before Dennett made a big issue of "filling-in",
why would anyone have thought it was a particularly questionable
thing to say?

>Dennett's citations are not from Usenet; they're from textbooks or books of 
>philosophy, whose authors should be careful about what they're saying.

If they're from books, they're a pretty small fraction of the whole.
Perhaps if you look at more of what the authors say, they're careful enough.

>Hardin's (excellent) book, for instance, is an introduction aimed at
>philosophers to what is currently known about vision.  He should (and
>normally does) carefully distinguish what is known about vision (e.g.
>that the blind spot is not directly perceived) from theories about why
>it is not ("filling in").  If he doesn't do that, how can his readers
>build reasonable, well-informed theories of their own?

I take it you're read Hardin's book as well as Dennett's.  Do perhaps
you can explain just what view Dennett thinks Hardin holds and give
me some reasons to think Dennett is right.

>One of Dennett's major points is that we overstate what we know about our
>own perception; we get the facts wrong, or don't distinguish the facts
>from theorizing about the facts.  That we don't see the blind spot is a
>fact.  That it gets filled in is a theory, and needs to be argued for,
>not assumed, and certainly not enshrined as the usual, neutral way of
>talking about the phenomenon.

Is it a theory?  Sure, it might be, but it doesn't have to be.
And if it _is_ a theory, what theory is it?  When Dennett tries
to say, he comes up with stuff I'm pretty sure is not believed
by Hardin or any of the other people Dennett mentions.  ("Figment"
is not Dennett's only attempt, just the most outrageous.)

>>Now, when someone talks about "filling-in", we can think about what
>>they say in more than one way.  We might try to figure out what
>>they're talking about, and, sure enough, we find that there is a 
>>blind spot and that we're not normally aware of it.  We might then
>>wonder whether "filling-in" is really the best way to describe this
>>or just what this talk of filling-in really amounts to.  
>
>Exactly.  That's just what Dennett is doing, IMHO: wondering whether
>"filling in" is the best way to describe what's going on. 

Dennett has not confined himself to wondering whether it's the best
way to describe what's going on.

>     If he hadn't
>read these authors "the wrong way", if he had just cut them some slack
>and let them write sloppily, he wouldn't have stumbled on such an
>interesting question.  

How do you know their writing _is_ sloppy, if you look at more than
a few sentences out of context?  Moreover, Dennett doesn't stop at
thinking it's sloppy (if that's even part of what he thinks at all) --
he tries to tie it all into the Cartesian Theatre.

>>Indeed, I find it difficult to determine just what view Dennett thinks
>>Hardin and the others hold.  When Dennett tries to say what it amounts
>>to, he comes up with something so ridiculous (see e.g. what he says about
>>"figment") that I find it hard to believe that anyone holds such a view.
>
>Sure, figment is ridiculous; also very amusing.  But it has a serious point:
>if this talk of filling-in doesn't mean that, what does it mean?

I have suggested one alternative.  Many more are possible.

>Why talk that way if there's a better way of talking?

If there's a better way, perhaps Hardin can use it without changing
his views at all.

>Or if one doesn't accept Dennett's alternative, why not?

Dennett has decided to make some claims about the views of Hardin and
others, and I'm addressing how well Dennett has backed up these claims.
I'm not trying to argue that Dennett's alternative is worse.

>>Perhaps Dennett thinks they don't hold _any_ clear view.
>>But if so, he doesn't do much to show that either.
>
>Is his task to give proofs that other authors hold particular views,
>or to explain how consciousness works?

You've tried to make it a matter of proof.  That was never my
intention.  What I said was "show", a word you were happy to
accept when saying that the answers to my "has Dennett shown"
questions were "yes".  Dennett doesn't confine himself to
explaining how consciousness works.  He also make a number of
claims about how other people see the issues.  In my 1st article,
I was addressing the claim, which even seems to be from an
article written by you, that

  Dennett shows (in _Consciousness Explained_) that the notion that
  the brain fills in some detailed picture of what the eyes see,
  even neatly airbrushing over the blind spot, is a fantasy, a
  relic of the Cartesian Theater.

Note that "shows" is already there.  So I asked whether Dennett
has shown (a) that anyone interesting actually holds the view
that the brain fills in or (b) that this view _is_ a relic of the
Cartesian Theatre?

But Dennett has not shown that anyone actually holds this fantasy
view, nor has he shown that any views that are actually held are
in fact relics of the Cartesian Theater.

-- jd
