Na....      

The best you can say is that perception exists.  The object of ANY perception is subject to scepticism.   As you all know, I think that scepticism is a null argument - it destroys itself.  The problem is not whether it is right (its not) but why our common sense view can be undermined by it.   Descartes answer that we have god there as the ultimate guarantor of reality and our 'true' perception of it is, as we see from this board, a highly controversial solution.  It is neither proven nor disproven. 

So lets go back to the only thing we know - perception exists.  We also know that - as far as we can perceive and rationalise - the only things capable of perception-as-a-propositional-attitude is a brain;  and the only thing capable of manipulating propositional attitudes is a brain developed to approximately the degree of our species  (its a scale - chimps and dolphins are close, maybe 'up there' with us).   Sea Urchins do not (we believe) have conversations about dualism: but even 'primitive' tribes of humans lost in New Guinea or Amazonas do.  There is no doubt that the brain is a centre of things mental. 

The next question is whether there is anything 'beyond' the physical make-up of the brain that can be associated with mentality.  Luckily, no society far enough advanced scientifically to both ask this and to have the experimental means to probe it... no such society is so morally degenerate as to actually DO experiments to pursue the question.  The upshot is that we have little in the way of a corpus of observations on which to theorise.  (Patton alluded to this in his 'resurrection' thread).   However, with the exception of some anecdotal stuff, heavily hyped with emotional prejudgements, we have nothing to suggest that there is anything other than the physical organisation of the brain to account for consciousness.  Note that we are coming close to an account of the way the perception modules work - has anyone found on the net that amazing diagram of the various functions of the visual cortex and their interactions  (sorry, I can't remeber who produced it)?  We have some good theories of how the brain shoots of commands down the nerves to produce actions.  What is lacking at present is the bit in between!  But the input and output functions are patently physically based - the central processing is described by many theoretical models - multiple drafts, fame-in-the-brain, reflexive connectivity, hermeneutic processing, etc.  But none of the research programs stemming from these seems to include a search for the interface with 'spirit stuff'....  unless of course Templeton has some people on it.   What I am saying is that insofar as it gives us a direction to investigate, theories that start to account for the few observations we have and ontological parsimony...  a monist approach wins hands down.

Its pretty close to an Argument from ignorance to claim that because you can't observe your brain that it doesn't have to do with your thoughts.

Empirical evidence shows that we can tweak thoughts through material methods (damaging or fixing certain areas of the brain, or introducing chemicals).  The Dualist has to provide an explanation for the regularity of what happens when certain areas of the brain are affects and they produce the same result.

Assuming our perceptions are accurate, of course. If not, the brain may be just as imaginary as anything else.

Let me be careful here to distinguish our facility for doubt (evolutionarily useful, scientifically fundamental) from methodological scepticism (destroying knowledge, paralysing discussion).   Scepticism is non-rational because it contains an internal contradiction.  The standard argument for perception scepticism is along the lines of a dialogue...

a.  I know I have hands
b.  Do you know that you are not a brain in a vat (being manipulated by an evil genius, etc)
a.  Of course not
b.  But you agree that if you don't know that you are not a brain in a vat, then you can't know you have hands,
a.  (O dear...)
b.  Therefore you don't know you have hands

The problem with the argument is the conditional.  It tries to establish the principle that if you don't know something on which some other knowledge depends, then you cannot know that other knowledge.  The common sense response is that we all know squillions of things without knowing their logical antecedents.  But the problem for the sceptic goes deeper, because (to steal his approach) we cannot know that the evil genius isn't messing with our powers of intellection as well as the inputs to it.  And if we apply the sceptic conditional using this, we cannot know that what we are inferring is correct - the argument can be applied to the sceptical argument itself.  Thats why I say it is non-rational, because according to its own terms, it cannot be argued as a rational sequence.

Yeah, it took me a while to get this. Or rather, it took me a while to be comfortable to say "I know x".

When you get a total skeptic its useless.  Someone like Zuk is one of those. He will be happy to expound upon the validity of some political theory, but then turn around and question all of existence - so what good is any of his wasted breath on politics?

This returns us to the Inference to the Best Explanation, which Callum can flesh out more than I, but basically it is no crime of logic or philosophy to declare that some things are known for the purpose of moving on to other things. Especially when those known things are fairly universal (e.g., we all experience ourselves as human beings with heads and bodies,on a planet in space that is affected by gravity. Among other things.)

We can trust our observations, we just need to question our interpretations but not to the point of negating everything.  So, we can admit that gravity exists since we all experience it, we just needed to debate on the cause. But the minute someone declares that gravity may not exist, and we are just imagining it, we have lost all reference.