This, at least, is an interesting discussion.
It definitely points to the first assumption we have to choose to make: whether or not our sensory data is indicative of anything 'real'. And it refers to another assumption we're required to make: that other entities exist, which we become capable of communicating with.
If we were unable to make the first assumption, we would be neither able to survive, nor learn anything new. If we are unable to make the second assumption, we become solipsists. Yes, these are assumptions; but they are vital assumptions, necessary to thrive and survive in the perceived real world.
This leads us to a better understanding of the actual problem: does it matter if there are 'real objects' in reality or not? Indeed, does it matter if the perceived reality is a real reality or not?
Unless we make the assumption that we are solipsists... we have to settle for communicated conformation of our own sensory realizations. Yes, it is true that there could be six billion brains in vats, all being fed a virtual reality of sorts - but that reality is no less real for that. No one bypasses the laws of this virtual reality, a-la Matrix; no one experiences anything beyond this virtual reality. So we're basically left with either deciding all this isn't real - which, at best, is an irrelevant and meaningless choice to make, and at worst, could be fatal - or deciding it's real enough, and carrying on accordingly.
I agree with Geoff inasmuch as saying that any kind of 'absolute realism' is real is an indefensible position... we just can't know if it's true or not. However, that's not to say that indirect realism is impossible. It's just to say that we have absolutely no way of knowing.
Perhaps 'practical realism' should apply - that for ALL practical intents, we have to accept that we indirectly perceive a reality which is practically real. Yes, that sounds like a lot of assumptions and "it'll do"ism... but that's what we get.
It is the only reality we're capable of experiencing, and the only reality which can be explained and described using logical rules, after all. "True reality" might very well follow no rules at all, but we have no way of even vaguely perceiving such a reality, so other than idle speculation for entertainment purposes only, there is no point in discussing any reality other than that which we perceive.
Now, come the day when a Neo-like figure breaks physical laws left and right, or the day when the Holodeck grid becomes visible through our city streets and country lanes, we'll have to seriously re-think the nature of reality. But until that day comes, we have to accept the reality of the world which we perceive, because we have nothing else.
