The Kripkean Response to Kripke’s Modal Argument against Physicalism

In fact unless the dream brain is radically different than their actual dreaming brain, if the dreamer knew all of the physical facts he would be able to deduce the relevant facts about awareness…
Exactly! And the only available physical facts within the dream are facts about the dreamed objects, together with the private experience of the awareness of the dream.

Within the dream, I deduce that the awareness arises outside of the dream, whereas you deduce that the awareness is entirely a phenomenon of the dream brain.

You are asserting that my awareness of non-physical awareness is not an available fact. But it is available to me.

No amount of consideration about zombies or dreams will ever show that physicalism is false.
Scientific laws model aspects of reality. It is thus in the nature of scientific laws that the operation of their models can be simulated. Therefore, anything that is true in science must also be true within a computer simulation of the scientific model.

This shows that any statement that is true in physicalism must necessarily be true within a virtual world that models physical laws. It also shows that, if physicalism is true, such a virtualization is possible.

Physicalism, it turns out, cannot be true in any virtual world, and thus it is actually inconsistent with physicalism. Physicalism refutes itself.

1. there is something inconsistant in your appeal to virtual worlds, since you admit that some mental states will be brain states in the actual world.
Not quite, I admitted that my thoughts would correspond to brain states that were consistent with physical laws. I didn’t go so far as to say that my non-physical awareness of those thoughts would be brain states. Awareness is not a thought.

I can think “I am aware!”, but that thought isn’t aware, rather I am aware of the thought.

The physical world is a mathematical abstraction, a set of equations that describe consistent relationships between objects within our awareness. I hold that the “actual world” is not identical with the mathematical abstraction we use to model it.

I think that physicalism turns out to be equivalent to the statement that the actual world is identical with the mathematical abstraction used to model it.

Your statements about the unreality of non-physical awareness amount to an application of that principle to awareness, but I think that it actually holds in general. We end up with the only possibility for physicalism being a tangled hierarchy of mathematical models, a strange loop in which the abstraction can manifest itself.

This doesn’t follow. If I model a hurricane on my computer I do not have a hurricane in my computer.
You have something that, within the model, behaves exactly as a hurricane behaves.

If we model the physical world it doesn’t follow that there is consciousness in the model.
You have something that, within the model, behaves exactly as consciousness behaves.

So would such a simulated consciousness be real consciousness?

Let’s examine your current assertion that it does not follow that it has real consciousness. So let’s suppose we create a mathematical model of neurons and create a number of simulated brains, made of different kinds of materials.

1. A simulation done with pencil and paper (a time-consuming proposition).
2. A simulation done with a digital computer.
3. A simulation done with an analog computer.
4. A simulation done with manufactured neurons (a collection of analog computers, say, each of which models a neuron).
5. A simulation done with cloned neurons.
6. A simulation done with natural neurons.

In simulating the neurons, we can present them with data that model the physical world, just as our sensory organs do for our physical brains.

So, my question is, where in that progression does consciousness appear? And on what basis do you claim that it is in step n, but not in step n-1?

If consciousness is physical, as you assert, then you should be able to point to it. So what do you point to in step n that is not present in step n-1, and which is likely to have any bearing on whether it is aware?

I think that the idea of consciousness being a brain state (as opposed to being a property of the matter of the neurons) is that consciousness is, in fact, a mathematical relationship.

Is that not correct? Or are you saying that there is some specific part of the brain that is the awareness? I thought it was the relationship.

I would say that consciousness arises at step 5, though at that point it is no longer a simulation.
OK, so consider that these neurons have parts, and that these parts could be replaced one by one with prosthetics. What are the crucial parts of the crucial neurons that make brain states of neurons “real awareness”, but brain states that involve some semi-artificial neurons a mere simulation.

What is the fundamental difference between a brain state of “assisted neurons” and the brain state of purely natural neurons?

For example, suppose my mental function is supported by a medication that fills a gap, a defect in my neurons. Does this make me less human? Would you argue that because I might take such a medication that my awareness is a partial simulation and that I therefore shouldn’t be considered as feeling real pain?

The physicalist is commited to the claim that all of the facts about the actual world can be deduced from the a completed physical theory. There is nothing about the identity of the theory with the world…
In fact, there is that identity.

With respect to awareness, your assumption of identity between brain states and awareness arises because all of the facts about brain states match all the public facts about awareness. Your challenge to me is to present a fact about awareness that isn’t also a fact about a brain state.

In other words, it seems to me that you are simply denying supervenience and asserting that supervenience and equality turn out to mean the same thing.

If you think that physicalism asserts that reality is different from the set of facts about reality, then I wonder what fact about reality you have in mind which we can use to verify that.

I think that the answer to such a question is that, ultimately, we find something, as a referent of a symbol, that exists as neither a symbol nor as a relationship between symbols.

I think that such a “pure referent” is therefore necessarily private, awareness for example. “Matter” would also work, except that at least with awareness there is private knowledge that it actually exists. I don’t think there is any experience of matter apart from the objects of awareness, which objects are really just experiences of attributes, not of matter in itself.

I never said anything that would imply that semi-artificial neurons wouldn’t be good enough…though this is an empirical question…
Well, you said that completely artificial neurons weren’t good enough, and that completely natural neurons were good enough. I am just trying to figure out what physical characteristics you think are necessary before a person should be considered human, and whether one person should, by virtue of physical characteristics, be considered more human than another.

If it is an empirical question, then there must be some physical test of whether awareness exists. So far, the only physical test you have mentioned is that awareness exists if and only if the brain state is a state between (at least partially) natural neurons. But you seem unwilling to give any reasons for deciding that completely prosthetic neurons are unfit for supporting the relevant kind of brain state.

What I am trying to get at is that there is no physical test for awareness, in the ordinary sense of that word, and you are trying to create such a test by making arbitrary definitions about the identity between qualia and brain states and thus are arbitrarily defining humanity.

How I am both denying supervenience and asserting that supervenience means the same as equality?

Sorry, I was imprecise. You are denying supervenience in that you are taking any evidence of supervenience as evidence of the stronger claim of equality, and then challenging those who believe only in the weaker claim to provide public evidence that your stronger claim is inappropriate.

I don’t think that and I didn’t say anything that implies that. There is the physical world, and then there is our description of that world in mathmatical/theoretical physical terms. The point is that there is no reason to think that a complete theory of our world will need to appeal to mysterious non-physical properties.
But that appeal is exactly what physicalism does. It is an appeal to what, in physics, are called hidden variables. Most physicalists are materialists, they think that the attributes arise because we are measuring local properties of a divisible, impersonal substance called matter.

The smaller problem with this view is that since we can only observe the attributes, and then only through measurement, so there is no direct evidence that matter exists. The larger problem with the view is that there are physical measurements, such as the Aspect experiments showing violations of Bell’s inequality, which are inconsistent with the idea that reality is a manifestation of local properties. “Local realism” simply doesn’t withstand the empirical tests.

The modern trend is to use the word “physicalism” instead of “materialism” because of the empirical problems associated with the idea that reality is made of matter. But the hope is to maintain the fundamental principle of ontological naturalism—that awareness is a mathematical relationship between impersonal attributes.

I grant that awareness is no less mysterious than is matter, however at least there is some evidence for the existence of awareness whereas there is evidence against the existence of matter, at least as it is usually thought of.

Furthermore, there is no operational difference between the physical properties of the world as we measure it and the measured physical properties of a simulated world within a simulation. You assert that lightning within the real world is different from a simulation of lightning within a virtual world, but the fact remains that every measurement within the real world would have an operational analog within the simulation and so there is no operational difference between the real electrical discharge as measured in the real world and the simulated electrical discharge as measured within the simulation.

If you have a theoretical basis that provides facts about the world, and if this theoretical description is complete, then every fact about the physical world should also be a fact within the theoretical framework.

But everything that exists within the theoretical framework is either a symbol or a relationship between symbols, there are no “pure referents” in the framework. Since pure referents do not exist within the theoretical framework, they cannot meaningfully exist within a physicalist interpretation.

I think that is really the crucial point of our disagreement.

I freely admit that it is surprising that awareness exists, but it would be far more surprising to find that it arises as a mathematical relationship between impersonal attributes. If that were the case, then it would seem that a book could be written in such a clever way that it would create the awareness of its reader.

If the “pure referent” as you call it turns out to be necessarily private that still doesn’t give us any reason to think that it isn’t physical.
What do you mean by “physical” in that statement? I prefer to say that there is no reason to think it doesn’t really exist.

The reason that it isn’t physical is that it isn’t a mathematical abstraction and thus cannot be completely expressed within a mathematical framework consisting of nothing but symbols and relationships between symbols. It cannot be modeled.

That is, there is a difference between things that exist and things that do not exist, but that difference is not entirely expressible as a fact within a theoretical model.

I seem to find myself in the position of Samuel Johnson. “I refute physicalism thus!” and I kick a rock. You may try as you will to reduce that entire experience to an abstract mathematical relationship (a physical model), but the thing that makes it real is my experience of it. And that awareness is the “mysterious “pure referent.

That is, we can have a complete physical theory, which includes all of the physical facts, but the thing that distinguishes the reality from the model is awareness.

If I dream of kicking the rock, it may be a dream rock and a dream toe, but the sensations of the rock, the toe, and the pain are all real. Maybe there is matter, and maybe there is not, but there is no need to bring this theoretical, ghostly “matter” into the picture at all. And in every theoretical model we can construct, we find that there really is no such thing as “matter”, there are only models of the ways that attributes interact.

Modern science, for the past 100 years or so, has advanced by discarding the notion that we are measuring an independently-existing reality and by replacing that with the notion that we are describing relationships between the measurements themselves.

It is very hard these days to conceive of a way that reality could possibly exist, independent of our measurement of it, that is consistent with the empirical evidence. As Einstein said, “These days, every Tom, Dick, and Harry thinks he knows what a photon is, but he is wrong.”

Now, you are right that I am assuming that physicalism is, and should be, the default view and so should be accepted unless shown to be false. But that is another argument.
It is strange to treat as the default view one that is demonstrably wrong in every case in which it can be tested, and which conflicts with physical experiments such as the Bell-Aspect experiments.

But my qualms with your theory don’t arise from my rejection of matter, but from your rejection of supervenience. You seemingly claim to have disproved supervenience in favor of identity.

I have given examples of scenarios, virtual worlds, in which the same available facts hold as premises as hold in the real world, and where the answer turns out (perhaps unbeknownst to those within the virtual worlds) to be supervenience but not identity.

Your response seems to have been to accept that your conclusions do not stand, but without showing how this inconsistency in the conclusions should arise from measurements done with available facts within the simulation.

To me, you and Dennett are each disagreeing with Chalmers in related but very dissimilar ways. I had proposed two classes of virtual worlds, some of which (as computer simulations) were intended as examples of Chalmers’s zombie worlds and some of which (as dreams) were intended as examples of zoombie worlds.

That is, I was modeling these worlds with concrete examples of particular ways of going about it, in hopes of finding out how some measurement done within these worlds would support the different conclusions.

Dennett also denies that you can separate the operational characteristics of thought from awareness, but then, unlike you, would have asserted that real awareness (as real as the awareness had by you or me) exists within the simulated zombie worlds.

So, I wonder how you would argue against Dennett, a fellow physicalist. What would you propose as an experiment to decide, between yourself and Dennett, whether the simulated intelligences had real qualia?

What is the appropriate physical test for awareness?

I suspect that Dennett would be as unhappy as I am with your defining qualia as necessarily involving “wet matter”.

I am afraid that I don’t really understand what you are getting at in the rest of your comment. You seem to wan to say that there is consciousness “in the dream” but that makes no sense! There is consciousness in the world that the actual dreamer is located in but not in the dream world.

Sorry for the delay.

The point is that physicalism asserts that every fact in reality corresponds to a fact in the theoretical framework.

Physicalism applies to the virtual world, because everything in that world corresponds to a fact in the physical framework. In a complete simulation of the theoretical framework, every fact in the framework will correspond to a fact in the virtual world. Because the theoretical framework is simply a mathematical model, such a simulation is possible.

You assert that there is some “physical dreamer”, but that assertion only seems to make sense within physicalism as saying that there is some aspect of the theoretical framework that corresponds to the physical dreamer. There is, within physicalism, no real dreamer in any sense other than that.

But that aspect of the theoretical framework also corresponds to an object within the dream (i.e. I can dream about myself).

That is, there is no actual substance in physicalism, you never transcend the abstract theoretical model to talk about anything that actually exists.

The meaning of the word “exist” does not correspond to facts in the theoretical framework. That is, a completed theoretical framework will still not be able to show that reality actually exists.

Idealism escapes that by asserting, contrary to physicalism, that there is something (namely awareness) that exists in reality but does not correspond to anything in the theoretical framework. It is only because idealism is *not* a physicalism that awareness can thus enter the dream from the outside.

In idealism, the objects of the real world actually exist, because they are objects of awareness, whereas in physicalism they never transcend the abstract, because there is no fact in physicalism that is not a fact within the abstract theoretical framework. Physicalism turns reality into a mere abstraction. In idealism, real objects actually exist in a meaningful way (e.g. when you kick a rock you are aware of it in a way that isn’t just theoretical and abstract).

If idealism is right and tables and chairs are simply ideas then physicalism as I understand it could be re-interpreted in the right way and still come out to be true.

You see, this is the kind of statement that I think gets it exactly backwards. It is in idealism that tables and chairs actually exist (i.e. we can be aware of them). In physicalism there is no fact about a table or chair that does not correspond to a fact in the abstract theoretical framework, thus it is in physicalism that the tables and chairs are merely ideas.