Re: Original Sin

Richard Dudley wrote:

Well that does absolutely nothing for me to clarify how its
'obviously' wrong. Newtonian mechanics doesn't involve guardian angels
for instance, whereas QM does involve observation by human beings.

No it doesn't. (Except in the null sense in which every
scientific activity involves observation by human beings.)

Care to explain why ? Seems either my or your understanding of QM is
seriously broken - if it turns out to be mine, I'd like to correct it.

Well, e.g., I have on my shelves a very nice book called
"Quantum field theory in a nutshell", and its description
of the physics doesn't involve human observation anywhere,
and this is pretty typical these days.

(Let me insert a disclaimer at this point: I am not
in fact a physicist, and it's possible that some or
all of what follows is wrong or poorly explained.
In fact, it's *certainly* poorly explained. If there
are any real physicists reading who would like to
comment, I'd be grateful.)

The old-fashioned (and still convenient) way of looking
at QM is to say: you have this thing called a wavefunction,
which is a vector in an (infinite-dimensional) Hilbert
space, and it evolves over time according to Schroedinger's
equation, and every now and then we human beings hit it
by making an observation, which means that the vector
gets projected onto some randomly selected eigenspace
of a certain linear operator, and what we observe is
the corresponding eigenvalue. That certainly does involve
human observation quite fundamentally.

But very few physicists these days think that observation
is fundamental to what's really going on. Instead, you
get ideas like this: "measuring the x-position" of an
electron just means allowing it to interact with the
rest of the world in such a way that the Wavefunction Of
The Universe afterwards tends to look like a linear
combination of components each of which involves one
particular "x-position" of the electron in combination
with one particular configuration of the rest of the
world. Operations that don't have that sort of property
just don't get called "measurements", and that's all
the mystery there is to measurements and collapsing
wavefunctions and all that stuff.

Well, perhaps not quite all. The question arises: how
come the universe mostly looks classical to us? Which
turns out to mean: how come so many of the things we
do with electrons behave in that sort of way? When we
do the famous two-slit experiment, why don't we see
a whole interference pattern of detection for *each*
electron or photon that goes through the slits?

Well, what would that mean? It would mean that the
interference effect "persists" right the way up to
the macroscopic level at which our brains and bodies
mostly operate. But there's too much noise for that
to be so: too much messy environmental interaction.
An individual photon may be (trivially) coherent
and therefore able to interfere with itself, but
the rest of the world isn't, and the result is that
those interference effects mostly go away just as
interference effects mostly go away when you use
incoherent white light instead of single photons
or coherent monochromatic light from a laser.

(The usual term for this is "decoherence", and a lot
of work has been done on it. My understanding of it
is pretty shallow. The Wikipedia page on "Quantum
decoherence" isn't bad.)

The practical upshot of all this is that almost any
interaction of nice simple quantum systems like individual
electrons with the big bad world leads to a whole-world
wavefunction that looks more or less like one of those
linear combinations I mentioned before, and hence like
a linear combination of "collapsed wavefunctions", and
therefore (adopting the Everett view for a moment, because
I happen to like it) the world is approximately made up
of a superposition of "worlds" in each of which the
macroscopic world sees a single position for the electron,
or whatever.

I had a little browse, but wasn't successful in finding a
defence of the claim that consciousness creates reality.

I would not expect to find a defense of such a claim myself, what I'd
expect to find was the building of an argument from experimental
results which left this claim as the most reasonable conclusion.

That would *be* a defence of the claim.

In your estimation, sure. Not in mine - I make a distinction between
building a hypothesis from evidence (the scientific method) and
stating a claim which then is subject to objections. The latter is
what I term a defense of a claim; in the former there's nothing to
defend and there are no attacks.

I'm not sure what the content of this distinction is: whether
the hypothesis is arrived at before the evidence arrives or
after, perhaps? In practice, hypotheses are formed when some
but not all of the relevant evidence is in; defending a claim
against objections is just one variety of examining the evidence
to see how well a hypothesis is supported.

The Amazon browse-inside thing only lets you read something
like 5 pages. I expect you can work around that by waiting
a day between blocks of pages, or something.

Not so in my experience. It allows a search, from which it permits
going forward and backward 2 pages. So if I want to read a book, I
just get it to search for the page number I want, which generally is 3
pages ahead of the last page I've read. The page numbers I search for
tend to increase in multiples of 5. This works until a message comes
that they won't allow any more reading.

Oh, I see, so they let you read N blocks of 5 pages at a time
(or whatever it is), not just one.

I think what Dianelos actually meant is that the conclusion was the
most reasonable one, not that it was literally the only possible one.

That may be what he meant, but it isn't what he said.

Yes but what he said is obviously not to be taken at literal face
value, so its reasonable to interpret it as a form of words pointing
to something else.

It's happened often enough that Dianelos has said things
that seem to me silly when taken at face value *and has
turned out to mean just what he says* that I'm not too
anxious to go looking for nonliteral interpretations of
his words until I know I need to.

And
of course "most reasonable" is always relative to one's
prior beliefs.

I disagree here, its relative to one's prior experience,
quite different to one's beliefs.

The perceived reasonableness of a conclusion is affected
by experience, but that effect is mediated by the beliefs
one forms in the light of that experience. But "beliefs"
is probably too specific a term; I don't mean to refer only
to changes in mental state that are expressed explicitly
as propositions that are explicitly believed or disbelieved.

Since Dianelos is starting out with a very
strong commitment to theistic idealism, I get very little
information from the fact that he read a book and thought
it fit better with theistic idealism than with any other
theory. But if he says that some book actually presents a
compelling argument for idealism (not specifically theistic
in this case, as I understand it) that's more interesting.

'Compelling arguments' in my experience simply do not exist. What
compels people (to update their paradigms of reality) is experience,
not arguments.

Arguments are part of experience, and they can perfectly well
lead people to update their ideas of reality.

I'm not sure where you're coming from in citing the
book's authors as saying their conclusions are tentative. Are you
saying that means they're not really sure of their conclusions?

I'm saying it suggests that they don't think that the evidence
they've presented makes their conclusions inescapable.

--
Gareth McCaughan
..sig under construc
.

Relevant Pages

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