Rabi has a nicely existential post over on wockerjabby. The interesting bit for me is the first paragraph:

I've been having trouble with reality lately, even more than usual. there's always a seedling of doubt burrowed in the back of my consciousness that tells me that nothing beyond my reach exists at all, that it's all a great spherical projection or hallucination or mirage, and if I were to shake my head too hard or trick the world into thinking my eyes were closed, everything beyond the stretch of my fingertips would disappear into static.

In a sense, her suspicion is right. The world out there is just a jumble of stuff. It becomes meaningful -- resolves into objects and forces and so forth -- because we interact with it, either by sensing it or thinking about it or acting on it. The world can't interpret itself.