Seasons

Ulrike:

Ah, I think I understand your objection better now!

The claim is that (A) in message 3753 implies (B). The argument itself therefore does not need to presuppose either (A) or (B). In fact, the argument is trying to establish that both are false.

But why would anyne thingk that (A) implies (B)? Well if subjective experience can be completely reduced to brain states, then then a complete theory of the relationship would imply all truths of the form, "Brain states of type X corelate with subjective states of type Y." If the theory is really complete, it would be able to describe what subjective states of type Y are like. How complete would a theory of arthropoda be that was unable to say what arthropoda were like? Now, Bevrina should then be able to find out by experiment what brain states people are in when they see red; she then goes to her Complete Neurophysiology book and finds the description of the subjective states that correspond to brain states of that kind. She can do this by reading (and applying) the theory, if there is such a theory.

But many people (including you, I gather) will object to the idea that she could learn what it is like to experience red by reading a theory book. For example, many people believe that the subjective (inner, experiential) appearance of redness is ineffable; it can't be described. They will conclude that no such book can exist, and no such theory can exist. In fact, many will argue that there is no way to know whether two identical twins with normal vision actually have the same inner experience, even though they are looking at a similar patch of red paint under similar lighting conditions. If they are right, then Bevrina could know all the neurophysiology there is to know, but she will never know what her friend Ekirlu experiences when Ekirlu sees something red, even though she has a scanner that tells her exactly what brain state Ekirlu is in at that moment.

But if
(i) Bevrina knows exactly what brain state Ekirlu is in, and
(ii) Bevrina knows the entire theory of brain/experience corelations, (and is intelligent enough to apply it)
but
(iii) Bevrina cannot figure out what Ekirlu is experiencing,
then it would seem to follow that
(iv) The theory of brain/experience corelations that Bevrina is using is incomplete.
For if it were complete, then it would tell her what a person is experiencing, when they are in the brain state that Ekirlu is in.

It is the believer in complete reductions of subjective states to brain states who is committed to (B).

Bev, Psimagus:

It is not necessary to read that very book. Virtually any recent textbook in Quantum Mechanics will have a chapter with a list of fundamental postulates. I like the CDL because is very clear and thorough. On the other hand, it would be nice if we were all working from the same text. You could borrow it and Xerox the passage in question.

Here's an argument, due to Thomas Nagel, which is similar to the Bevrina argument above and may therefore cast light on it (I am putting it into my own words):

Bats hear notes which are far too high for humans to hear. Let's say a Bat hears a note at a frequency of 35,000 Hertz; no human could hear such a sound. What does it sound like to the bat? What is the bat's experience of the sound like?

If we had a complete theory of the relationship between brain states and experiences, then we could scan the bat's brain and apply the theory to find out what the bat was experiencing.

But again, many people will claim that the bat's experience is ineffable. They will say that we can never know what a note of 35,000 Hertz sounds like to a bat.

If they are right, then we will never be able to have a complete theory of the relation between brain states and conscious experiences, for a complete theory would tell us what 35,000 Hertz sosunds like to a bat.

If you think they are wrong, please explain to me how we are going to scientifically determine what 35,000 Hertz sounds like to a bat.

Psimagus, Bev:

In fact, here is a quick list of six postulates that you can find on the net, absolutely free!

http://vergil.chemistry.gatech.edu/notes/quantrev/node20.html

(i) Bevrina knows exactly what brain state Ekirlu is in, and
(ii) Bevrina knows the entire theory of brain/experience corelations, (and is intelligent enough to apply it)
(iii) Bevrina cannot figure out what Ekirlu is experiencing,
then it would seem to follow that
(iv) The theory of brain/experience corelations that Bevrina is using is incomplete.

So a theory is incomplete if reading about experiences based on the theory does not result in actually experiencing them? In (iii), Bevrina would be able to describe, based on her books, what Ekirlu is experiencing. That doesn't mean that she, herself, knows how it feels. I can read a description of a cocaine user's high, for instance, and possibly relate to SOME of it, but unless for some odd reason I try cocaine, I still won't know how it feels.

It seems to me that you've assumed two things. The first you stated, "We have a complete theory of brain/experience correlations." You've included a second assumption. "A complete theory of experience means that knowing the brain states is the same as experiencing them." In other words, you've assumed the very absurdity you try to use to argue down that a complete theory could exist. I don't see that absurdity as following logically from the existence of a "complete theory". What does follow is being able to describe how it would feel, in words. That's not the same as actually feeling it.

So a theory is incomplete if reading about experiences based on the theory does not result in actually experiencing them?

No, I wouldn't want to say that! If I said it before, I take it back! What I meant to say was, that if a theory of the relation between brain states and conscious experience was complete then it would be able to say what it would be like to experience being in that state; for example, what it would be like to experience red. In the example, Bevrina would know what it was like to experience red. I didn't (mean to) say that she would actually experience red, just by reading the book; indeed, she would presumably not experience red, since her brain is somehow unable to do that; this might be changed by brain surgery, but presumably not just by reading a book!

Analogy: Reading a book about life in Iraq might give me some information about what it would be like to live in Iraq, but, unless it were a truly remarkable book, it would not allow me to actually experience living in Iraq.

Dear Ulrike: Oops, I meant only the first sentence in the above to be in maroon; it is a quote from you, message 3766.

You go on to say,
"In (iii), Bevrina would be able to describe, based on her books, what Ekirlu is experiencing. That doesn't mean that she, herself, knows how it feels. I can read a description of a cocaine user's high, for instance, and possibly relate to SOME of it, but unless for some odd reason I try cocaine, I still won't know how it feels."

Indeed, it is possible to say some things about inner experiences. But if there are also some things you cannot say, then the theory is incomplete.
I don't think that even the most extreme believer in ineffability believes that we can't say anything at all about inner experiences. Likewise, even the most extreme believer in their being some non-physical aspect of inner experience does not doubt that there are some corelations between brain state and experience. But as long as there are some aspects of inner experience that cannot be described by a theory, that theory is incomplete.

You go on to say:

It seems to me that you've assumed two things. The first you stated, "We have a complete theory of brain/experience correlations."

I don't think it's fair to say that I stated that we have a complete theory of brain/experience corelations. I assumed that, for the sake of argument. I did not endorse it, I did not claim it to be true.

The form of argument known as reductio ad absurdum consists in refuting something by showing that it implies something unacceptable. In order to show that A implies B, one sometimes assumes A as a hypothesis, and shows that one can deduce B from it. One is not committed to the truth of A, only to the fact that B follows from A. So in

AAARGH!!! This wretched system truncated several paragraphs off my previous post! I am too tired and frustrated to retype them right now! Maybe tomorrow. [sigh]

Walk in Beauty, Irina

Look, I get the reductio ad absurdium. For the purposes of the argument, you assume something and try to show it leads to an absurd conclusion. Got it. Many many times over. Where we differ is that I don't agree with where you say the assumption leads.

Reading a description, no matter how complete, no matter that it is from the most perfect theory out there, is not the same as experiencing it. So she could "know" the experience in the sense of being able to write out facts from rote, but not in the sense of knowing what it feels like. Just like I could write out the effects of cocaine use and still not know what it feels like.

But as long as there are some aspects of inner experience that cannot be described by a theory, that theory is incomplete

Your definition of completeness still seems to render every possible theory incomplete. Which if we're looking at Gödel and systems of logic is certainly the case. But in terms of physical systems, this definition is far too stringent. Like the theory of quantum mechanics is not complete if it doesn't tell me what it feels like to be a particle in the double slit experiment.

I'm sorry, I misunderstood where your objection lay.

If there is such a thing as 'what it feels like to be a particle in the double-slit experiment,' and Quantum Mechanics doesn't tell me what it is, then there is a sense in which QM is incomplete, I should think.

I don't want to argue about the correct use of the word "incomplete", however. I'm happy just to say, "There is a fact of which QM does not apprize us."

IF inner states are really nothing but brain states, then shouldn't there be a theory which tells us which brain states are which inner states? Well, maybe not; it may be that for some reason, there is a corelation, but we are unable to specify what it is. We can't know everything. If that is what you are saying, I would have to agree.

But then, I would also be a bit reluctant to agree that a computer is emulating my inner life. If I have no theory of the relation of brain/computer states to inner states that covers all the ground, then I am not in a position to assert that the computer is emulating all my inner states.

Specifically, suppose that someone says, "That computer is now experiencing red. It experiences redness in exactly the way you do. But don't take my word for it, check it out for yourself." He gives you the complete design of the computer as well as a moment-to-moment scan of what physical state the computer is in. How would you go about using this information to decide with certainty whether the computer was really experiencing redness the way you do?

Irina,

In fact, here is a quick list of six postulates that you can find on the net, absolutely free!

http://vergil.chemistry.gatech.edu/notes/quantrev/node20.html



Yes, I agree that these are standard postulates describing quantum mechanics, and I accept their accuracy. But I don't see that they in any way indicate that light only comes in waves, or that there is some sort of wave-particle alternation allowing it to change at will between wave and particle. They point to the simultaneous duality of wave and particle natures that has been the accepted model for the best part of a century.

My view of the double-slit experiment is very straightforward. A wave goes through two slits and is diffracted. It interacts with the detector screen in a punctiliar, probabilistic fashion. There is no particle that travels in a continuous trajectory (or several) from the source to the screen.

A wave could only go through 2 slits if it were not an indivisibly small unit. But the whole point of a photon is that it precisely is such an indivisible unit - a "quantum packet". You can raise or reduce its energy, but you can't analogise it to, say, an ocean wave washing through 2 slits in a breakwater, where some water can go one way, and some another. It may display some wave-like features, but it can't be split in half. All of it goes through both slits simultaneously. No-one knows exactly why or how, but it is evident that it does.

Photons demonstrably exhibit both temporal and spatial periodicity (since they possess both frequency and momentum,) and it seems far less plausible to me to dismiss either state, for the mere convenience of aligning our observations with "common sense". This apparent paradox may indeed give us cause to wonder greatly about the nature of photons (and quite possibly about the nature of numbers themselves,) but it doesn't change the fact that what we observe happening really does happen. One photon, two slits, both paths actually travelled. Yes, there is wave-like behaviour in the diffraction and frequency, just as there is particle-like behaviour in the mass<-2>2<0> and momentum<-2>1<0>.

Einstein's 1905 analysis of the photoelectric effect makes it quite clear that particulate photons displace electrons, causing a current to flow. If light were only a wave, we would expect an increase in the intensity of the light to effect the displacement of more energetic electrons. This does not happen. In fact, you merely displace more electrons, whose individual energies (at a given frequency) remain E=hv (where h= Planck's constant & v= frequency).

You can describe these wavicles as particulate waves, or as wavy particles - I don't mind, but your description of them as merely waves is simply inconsistent with the observed phenomena. They do travel continuously, and a single fermion (at any E or v,) passes through both slits at once.



<-2>1<-1>It is often stated that waves possess momentum - see section 3.3, page 38 of http://www.maths.reading.ac.uk/research/publications/Msc_dissertations/jemma_Shipton.pdf for why this is (at best) a grossly misleading oversimplification (entirely too non-ASCII to reproduce here!) Sound/water/pressure waves require a medium for transmission, and any momentum is confined to the matter that makes up that medium, not to the wave that passes through it. Electromagnetic waves (by virtue of wp-duality,) effectively are their own medium. Were light only a wave, it could not travel in a vacuum.

<-2>2<-1>It is often stated that photons are massless. This is only true if you seek a velocity-independent mass (ie: the "rest mass".) According to E=mc^2, a photon evidently has mass m = E/c^2, but dependent on its velocity. In terms of a "rest mass", E=mc^2 is invalidated, and must be reformulated as E=mc^2/sqrt(1-v^2/c^2) [or more neatly as E=sqrt(m^2c^4+p^2^c2) where v=velocity and p=momentum.] Outside of an Einstein-Bose condensate at O degK, there is no such thing as a photon "at rest", so I'll stick with the "old-fashioned" relativistic definition for this example.