I don't think I can phrase all the propositions in a way that will satisfy everbody. It seems continuing this discussion in this vein leads only to ever more verbose descriptions of the argument and more inquiry on the other side, but without much content added.
So will try to approach the whole thing a different way. I think this problem is not really a problem that can be solved by pondering pro and con arguments and coming to a "objective" conclusion. So my approach was maybe not quite right.
I think it's an issue of introspection, that is, a fundamentally subjective issue.
By this I don't mean, that there is no "right" answer, but only that this answer can not be directly communicated (or even less proven). It is a private truth. Like the truth "I am conscious.".
So instead of trying to make an argument for an "objectively true" answer, I will try to show that there is a truth that has no "hard" argument (in the sense of a logical "proof") in it's favor but seems to be a valid truth nevertheless. Like the truth that I am conscious right now. There is no argument that can convince me rationally of this. For my rational mind the sentence "I am not conscious." could well be true. It could just be another believe I hold, maybe because I believe consciousness is superfluous in the description of this universe. Nevertheless I know that what the sentence "I am conscious." means to me is absolutely true and I don't need an rational argument for this. In fact, searching for a rational argument for this will lead me nowhere (except that I maybe find out that this does not work).
So: Regardless of whether all empirical observations are dependent upon consciousness, certainly all of YOUR observations are dependent on consciousness. This conservely means you cannot make an observation independent of consciousness.
This does not prevent you from believing that there exists something independent of you. But what does "There exists something independent of me" mean if in fact this something can not exist as (part of) an observation you make?
How do you get from "My observation" to "something apart from my observation"? What do you "have" apart from your observations that can justify (to yourself) this step?
I can make all kinds of theories *about* my observations, but what does a theory mean to me that is not about my observations?
Such a theory seems to be arbitrary and empty to me.
Please don't debate this (it is a subjective statement after all), but maybe instead try to convey what a theory that is not (exlusively) about your observations means to you, why it does not seem to be empty to you.
I sincerly can't understand this.
To prevent missunderstanding: I'm not saying materialism does not make statements about your observations, but it also make statements that are held not to be dependent on your observations and thus effectively outside ouf your observations. I'm referring just to the latter part of materialism.
I agree that if I dismiss all theories that are not about my observations (in the sense of "derived from my observations" and "making predictions about my observations") this in some way leads to solipsism.
But only in so far that I state that "only consciousness exists", not "only the particular form of my consciousness as it is now", exist. "Others" people's consciousness maybe in fact not fundamentally different from my consciousness but just another expression thereof and vice versa. I'm not stating that this is true, but I may one day discover this to be true (because the other person and me both realize that we in fact are the same consciousness, by merging our identities) - so I can not rule it out. So it's not "ego"-solipsism (what I currently identify "me" to be is all that there is) but "I am"-solipsism (that what underlies all indentifications and what is immutably true - even if my personality might totally change and maybe merge with others - is all that there is), which I think is really not what is commonly understand as solipsism but more akin to the idea of Brahman in eastern philosophy.
It's true, though, that as long as I don't get to have an experience that makes me sure that "I" (in a very general sense) and another I are in fact fundamentally the same, I can not be *sure* that there are other beings that have subjective experience similar to mine. But I believe it is a good theory to assume they do have similar experience, because it would explain their conscious behaviour and someday I might be able to confirm this.