Politesse
Amor Vincit Omnia
And here's my trouble; I find "something giving input to our sensory system" a much more reasonable definition of existence than "I can prove it." Of course you can't. We have no unmodified access to reality and I disagree with very little of what you've written here concerning the limitations on perception. But they are limitations on perception, not existence. If existence has any meaning, it must be applied to the extrasomatic world we know exists through the practice of independent confirmation, not the sensory world of agreements and feelings that we create culturally varying consensus realities around. If you believe that the world of perception isn't trustworthy, why would you grant it the sole title of existence?
As you say, we could all be in a computer simulation. If we are, to say that "ideas are the only thing we know exists" would be utterly ridiculous, since the last thing a computer program should trust is the autonomy or tangibility of its mind. But it does know, as we know, that its input must be coming from somewhere. The applicability of your metaphor requires that the listener agree that the computer simulation must itself be false if it has a "Real" programmer and hardware somewhere out there. But if that is the case, why would we call the program "the only thing we know exists", to the exclusion of the actual source of that program? For all we know, this whole confusion of trying to figure out quarks and muons and other oddities of mathematical precision and material contradiction might just be exactly what happens when a computer tries to "examine" its own hardware. That that still leaves us with real hardware somewhere, and computer and program both exist in any meaningful sense, not because of the computer's thoughts but because those thoughts have an object whether it can directly sense that object or not.
