If you need a specific disagreement POV to answer my question, then I'll say Belz.
I'm flattered!!
How does your philosophy differ from Belz' (as far as you can tell) and what difference does it make to your actions?
I'm going to chime in and just make a little summary of how I see this whole debate:
<cracks fingers>
In order to even try to understand reality, I have to have a working assumption. Otherwise I couldn't even formulate a question, let alone find the answer. A quick thought gives me two possibilities: "nothing exists" or "something exists". The former can't be of any use to me, because then no question could possibly have any meaning. Not only that, but it flies in the face of a very obvious fact: I'm aware of
something, so even assuming it's all an illusion, that illusion exists.
So we're left with the second assumption. Of course, then the question is: "what exists" ? Well, if I could refine my first assumption with an answer to that question, it would help tremendously. Again, I see two choices: "the world as I experience it exists in some capacity" or "It may or may not exist, but I can be sure that the observer, my mind, exists".
But assuming the latter, that the observed universe is suspect, leads to a few problems. First of all, if what I see is possibly illusory, then I'm left with the possibility that the other people I see in that world are also non-existent. After all, I can close my eyes and imagine fictitious characters that are nonetheless realistic in their behaviour. And since I can't experience
their mind, then they're just as suspect as the rest of it. That leaves just me.
But then, there are a number of circumstances that affect my mind, and I can see that my memory, my feelings and even my thoughts can be altered by those circumstances. Sleep deprivation, drugs, caffeine and even temperature are just a few of the things that can make my mind go awry. Obviously, those aspects of me are part of the world I observe, because they are directly affected by it.
So, what's left ? Well, I could retreat to Geoff's last position about it: "the subject", or "the I that observes". Well, here's the rub: it's just as subject to change as the rest, and my very ability to observe my own thoughts has evolved over the years and changed with context. This position is also pretty much what solipsism is, and everyone here seems to agree that it's, again, not very useful. Also, it's at least conceivable that this "subject" could be part of an elaborate simulation. So, maybe I'm just bits in a computer program.
Well, seeing as
something must exists and the idealist train of thought has led me to positing a reality that I could never experience anyway, I'll have to go with the
other refinement of my assumption: "the world as I experience it exists in some capacity".
If the world is real, it would be expected to be consistent, an expectation which is vindicated by the existence of science, something I can do myself. This consistency would be difficult to explain under idealism, and now it allows me to ask questions and find answers. It's already more useful than the other assumptions, isn't it ?
Now I can also consider that the people I observe are real and similar to me. Now, this is still compatible with dualism, but not for long, because then we have to deal, again, with the mind-brain dependency discussed above. Also, I'd say that a monism is simpler and more elegant than dualism, because it doesn't require two explanations and two sets of assumptions. So, not only does the world as I experience it exists, but I'm part of it. This fits rather well with my own experience, as I don't feel that my mind is "ethereal", or anything of the sort. It's also quite testable, empirically, at least in principle.
Call it materialism or physicalism or whatever, but it's the only path that gives me real answers and doesn't require mental gymnastics for me to maintain. Sure, the universe really
could be an illusion; it's
possible that I'm just a brain in a vat. But it changes nothing to
this reality, so in the end, it's the only thing I can ever hope to understand.