You can't get there from here

Victor Reppert has a recent post loosely summarising a number of problems for physicalism, which has set me thinking.  Following my usual practice, I comment directly on gobbets of Victor's post.
1. Suppose we are given a complete list of physical facts, facts about where all the particles are. The information, thus given is insufficient to determine a unique mental state that a person is in. There is no entailment relation of any kind to the relevant mental state.
Indeed.   This, I believe, is known as the anomalism of the mental.   A physicalist has to offer some account of why this is so.  Here is a suggestion that I'd like to receive comments on.  I start with the thought that our only contact with the mental is through language, typically propositional attitude reports.  It's not as if we have an extra sense by which come to know the mental.  For example, our visual sense is equipped with qualities like colour and shape.  We can pay attention to these aspects without seeing any object, and sometimes these aspects cannot be made sense of as objects, and we are unable to describe a scene in propositional terms.  Example.  In contrast, the mental simply manifests itself in ready-made propositions, or rather, sentences.  Indeed, a number of writers have asked the question,  How can I tell what I think till I see what I say?  This sounds like Lewis Carroll's Alice but it is in fact EM Forster.  This suggests to me the following picture.

Sentences here count as physical.  Sentences 'in the head' can be uttered.  Brain states are clearly physical.  So we have a causal relation labelled language production.  We have little idea at the moment how language production works, but at least it relates the physical to the physical, so we can have some hope that the methods of science will uncover more.  How do mental states fit in?   We all seem to believe that there are such things as mental states and that they lead to the production of utterances, but it's not at all clear how the dotted horizontal arrow does its work.  One possibility is to think of mental states as theoretical entities introduced to explain sentences just as particles and fields are theoretical, ie, not directly sensed, entities brought in to explain matter.  The horizontal arrow then represents some set of theoretical principles by which sentences can be derived from mental states, much as physical principles enable us to derive the behaviour of ordinary bodies from that of their particles.  On this understanding it's hardly surprising that we can't specify the upward pointing dotted arrow, though it does make sense that mental states appear to supervene on the physical brain states.   How close is this to eliminativism?   Quite close, I guess.
2.  In virtue of what is some physical state about some other physical state? This is the familiar worry about intentionality, a worry made more difficult by my claim that the kind of intentional states involved in rational inference are states in which the content is understood by the agent and put into a propositional format.
I suspect the only sense in which physical state B can be said to be about physical state A is if A is causally contributory to B so that B contains some information about A.  This seems to rule out a physical basis for intentionality, for we can think about things that don't physically exist.  I'm inclined to explain the 'aboutness' of thoughts by means of the 'aboutness' of sentences.  Again, our contact with thoughts qua mental states is through the sentences they produce.  The aboutness of sentences is a shallow syntactical business by which sentences analyse into subject terms and predicate terms.  Is this eliminativism with respect to intentionality?  You tell me.  I certainly take issue with Victor's characterisation of inferential intentional states.  I think he has things backwards.  For me the 'mental content' manifests itself in propositional format, ie, sentences, and then becomes available to be understood.
3.  In the case of mental states, I do not see how the physical states can possibly “add up” to any determinate mental state. There is a qualitative difference between the physical base and mental content, that no amount of investigation can possibly overcome.
I agree.  But I don't get from the physical to the mental by a process of accumulation like building a brick wall (Victor's metaphor in his original post).  
4.  Given naturalism’s commitment to the natural sciences, the naturalist must presuppose the existence of mathematicians as well as scientists. Therefore, some serious consequences follow from the indeterminacy of mental states. It would mean that what Dawkins means by atheism is indeterminate. It means that it is not literally true that Einstein developed his theories of relativity from Maxwell’s equations.*
This follows a quote from Daniel Dennett arguing for the indeterminacy of mental states.  Victor feels that mental states must be determinate else rational thought be impossible.  I say that inference operates on sentences and sentences are quite determinate.  Have you ever repeated a sentence over and over in the hope that its implications become clear?   The meaning of a sentence may be indeterminate---ultimately the meaning of a sentence is what it does to us, the changes it produces in our brain state, and this is certainly indeterminable with current technology---but it is sentences that are the primary bearers of truth, in that it is sentences that we judge true or false.
5.  More to the point, brain processes, composed as they are of meaningless chemical components, seem as inherently devoid of intentionality as soundwaves or ink marks. Any intentionality they would also have to be derived from something else. But if anything physical would be devoid of intrinsic intentionality, whatever does have intrinsic intentionality would thereby have to be non-physical. Sine the mind is the source of the intentionality of physical entities like sentences and pictures, and doesn’t get its intentionality from anything else (there’s no one “using” our minds to convey meaning) it seems to follow that the mind has intrinsic intentionality, and thus is non-physical.
This is a quote from Ed Feser.  There is something deeply amiss with the notion of intentionality.  It splits the world into two disjoint classes, the interpreters and the interpreted, processor and data.  But brain states are clearly simultaneously both processor and data.  How are we to understand this? Shades of Frege's object versus concept distinction perhaps?

* Actually, it isn't true  that Einstein developed his theories of relativity from Maxwell’s equations.  Certainly not GR.  SR starts with the observed constancy of the speed of light and derives the Lorentz transformations.  Earlier work (check this!) had shown that Maxwell's equations are Lorentz invariant.

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