Proof Mind is Fundamental and Matter Doesn't Exist

[Rational AKD]

I confess I have not bothered to read the entire thread.  But has anyone pointed out the fact that statement 2 does not follow from the previous claims?  If I cannot prove that something is false, that does not mean that it is actually possible.

it has been brought up and I addressed it... but i'll go ahead and answer it again for you. basically what's behind premise 2 is our epistemic limitations. you can't use the contents of our conscious experience to explain what is behind them. so you can only use information not gathered from experience. but as there's no contradiction or inconsistency of a world that only has a mind, solipsism can't be proven false. this means for all we know and could possibly know, solipsism is possible. to put it another way, solipsism could be true given all epistemic knowledge. so given that, it would of course be unreasonable to presume solipsism is impossible. as for the agnostic position, it could only be maintained epistemic possibility doesn't establish actual possibility if we can't use epistemic knowledge to claim knowledge of what's actual... but this would be nihilism, the belief we cannot know what's actually true. but this position is also self refuting because it makes a claim of knowledge of what's actual by saying 'we cannot know what's actually true.' since nihilism is self refuting, it is not a reasonable belief. since being agnostic about the possibility of solipsism in light of our epistemic knowledge, that for all we know and could know it is possible, implies nihilism; being agnostic on about the possibility of solipsism is unreasonable.
in stark contrast, it seems reasonable to suggest epistemic knowledge is good evidence of what is actual. thus the only reasonable position you can maintain is that solipsism is possible. now, this still doesn't as you say mean solipsism is in fact possible. but then again premise 2 doesn't state that either. it states solipsism must be most reasonably granted possible. this again doesn't eliminate the impossibility of solipsism as a possibility, but rational people shouldn't be interested in just any possible answer. they should be interested in the most reasonable one.

Furthermore, 3 is introducing more that does not follow from what was stated previously, because a mind might be a material thing.  Maybe your mind is all that exists, but your mind is a material object.  Thus, 3 would be false.

3 is actually the premise that disproves that. it's all about Leibniz Law of the Indiscernibility of Identicals. A and B are identical if and only if for everything that is true of A, B. if there is something that is true of A but not of B, then A and B are in fact not identical. so premise 3 states concerning mind, that it is possible for mind to exist in a solipsist (immaterial) world. this is shown true by the prior premises. it then states it is not possible for matter to exist in a solipsist (immaterial) world, which is true simply by definition. and from that we get to 4, that they are not the same and mind is not reducible to matter. so really you're objecting to 4, not 3. but I just explained why 4 follows from 3 and why 3 follows from 1 and 2.