Originally posted by Mentat
Make up your mind. Either the matrix is a dream world, or it is the computers. Either the thoughts of a person are (nothing but) the certain synaptic processes in their brain, or they are extra "subjective qualia" in a phenomenological world.
The matrix is a set of information structures existing in computers. These information structures are subjectively experienced by en-matrixed brains as a closed phenomenological world.
But one doesn't percieve a flower in the matrix. One perceives the flower in the real world (where their brain is). There is, in fact, only one world...and no flower.
But there is no "matrix brain". There is only the one brain, processing incoming signals in the form of electrochemical activity in the neurons and across the synapses.
I was describing the perception of a matrix flower, vis a vis a 'real' flower. The distinction is only to be made in the ontology of the source of the input to the brain. And there
is an objectively existing 'matrix flower'-- it is simply the information structures in the matrix which represent a flower.
But now the semantic problems will either come up, or be cut off at the knees...I do not think that the matrix flower, or the "hologram" of a flower is pretty, because there is no such thing. There is a real flower (actually there are billions of them), that I have seen before, and that I thought was pretty, not because I thought the sum of the processes in my brain was "pretty", but because the very way I was processing gave rise to the "pretty" sensation.
"Gave rise to the pretty sensation?" The processing doesn't
give rise to the pretty sensation, it
is the pretty sensation. (Sorry, I couldn't resist.
)
In any case, I know what you're trying to say with that statement and I agree. But clearly you must see that if it is brain processing P that gives rise to the "pretty" sensation, then it doesn't matter what the source of stimulation is so long as it illicits P. It doesn't matter if there's really a 'real' flower there or not. So if we're going to talk about a 'real' flower being pretty, there's nothing wrong with saying a matrix flower is pretty either; the circumstance of prettiness is identical in both cases. The 'real' flower is not what's pretty-- what's pretty is what's going on in the brain. So the existence of the 'real' flower is important only insofar as it acts as a generator of sensory inputs to the human brain which illicit perceptions of flowerness/prettiness by reflecting light in its characteristic way. The data structure we call the matrix flower, in this sense, is precisely the same thing-- it is a generator of sensory inputs to the brain which illicit perceptions of flowerness/prettiness.
My apologies. Still friends? 
Of course.
A world X is a set of physically existing things. If it were not, then we would never receive stimuli in the form of energy. Also, I wish to re-iterate that there is no "world" in our brains (physical or otherwise), composed of the sums of these stimuli (and the reactions thereto), which is the conclusion that you seem to be leaning toward. There is, really, no "sum" of these stimuli in the mind, but merely a set of processes that occur at different times, for different reasons, but which appear to have synergistic properties to them.
Well, this is the rub, isn't it? Can we meaningfully call something physical if it does not fit the criteria for physicality? If we can never observe something to exist (either directly or indirectly) in our observable physical universe, but we are given that it exists, can we rightfully call it 'physical'?
The point is that the notion of physicality hinges critically on our ability to know about something in our own physical world. Suppose for a minute that we are living in a simulated matrix world. Then there is, say, a chair sitting next to the vat that holds your brain, which is hooked up to the matrix computers. You, I, and everyone else living in this matrix world can never know about the existence of this chair. Do we still call it physical? If we do, then you have posited the existence of a physical thing which does not meet the criterion of observability. You, being unable to observe this chair, would of course say "there exists a physical chair that I cannot even in principle observe? Nonsense!"
I disagree. We could not determine the information in the computer as being a quark or an electron, unless it (the computer) incited in us the same experience that we have when we discuss or observe (you can't actually observe them anyway, but that's not too relevant (I hope)) electrons and quarks. We are being stimulated in the same way, but in this case there are no electrons or quarks (real or otherwise) that are the cause (or part of the cause) of this stimulation.
This came in response to the following paragraph I wrote:
We presume the most basic building blocks of our world to be quarks, electrons, and the like. If we were actually in a matrix, then there would exist a deeper level to the ontology of our world that we could not hope to know: quarks and electrons would actually be themselves composed of bits (or whatever) of information in the computer matrix. Everything we call 'physical' would actually refer to information existing in this computer. The things we call 'the laws of physics' would actually be rules existing in the computer code. And so on.
I don't see how your response negates any of my claims. If we have been in a matrix this whole time, who is to say that electrons and quarks even exist in the physics of the world that houses the computer matrix that we are hooked up to? Even if we assume the physics of the 'real' world and the matrix world are identical, your point still does not negate what I have said here. All the claims we make about quarks and electrons and the like would pertain only to matrix electrons and matrix quarks, because this is all we would have been studying. And despite our best efforts, we would not be able to tell that these electrons and quarks are really composed on a deeper level of information structures in the computer matrix.
Not at all. If you say that the immaterial mind itself is physical, then you require the homunculus, since a physical entity (a separate "mind", in this case) inside my brain is useless without an "inner eye" with which to percieve it.
Not at all. Suppose our 'real' brains sitting in the matrix vat operate exactly how you fancy them to operate, with Dennett's MDP and so on. Then we in the matrix have immaterial (unobservable) minds, which are simply our 'real' brains sitting in the vats of the 'real' world. You would like to call these brains physical, but they are unobservable to us even in principle. This creates a standard whereby it is acceptable to call unobservable things physical. Thus, by this same standard, we could call the abstract 'mind' or 'soul' or whatever a physical entity though we have no means of observing them; since we have defined these things to be physical, we do not have the traditional dualist problem of physical/non-physical interactionism. The mode by which this mind or soul or whatever operates is not important-- it is not by necessity evocative of the homunculan problem, for the same reason the matrix/brain example at the beginning of this paragraph did not fall prey by logical necessity to the homunculan problem. I could simply claim that this unobservable physical soul does not
produce subjective experience, but simply
is the subjective experience.
Besides, I find the two choices most unsatisfactory, since the first one refers to all that exists, which is redundant (anything that can be referred to exists (note: this does not preclude the use of words that don't really refer to anything, but are just words...it merely precludes actually referring to something, and that "thing"'s not existing)); while the second implies that there is a closed set of stimuli that make up "our world", when in fact there is one world, and every one of our brains is a part of that world.
By the way you are defining things, everything that exists is indeed physical. What is a word, but a set of electrochemical processes in a brain, or a pattern of ink on a page, or a set of electrical processes in a computer monitor?
It doesn't work for "the mind" (seperate from the brain) to be a physical or non-physical thing, it just can't exist at all (which is why Dualism is impossible, no matter how you redefine these terms). If it does exist, then there must be an inner homunculus to observe it, otherwise it's of no use to you, since you never become consicous of what's going on "in there".
The mind exists, axiomatically in fact. Let us define the mind as the complete set of subjective experiences of a particular person for a particular duration of time. You have simply described the mind materialistically in terms of Dennett's MDP, but you have not by any means shown that it does not exist.