Sure. But that's not true of cats / boxes, nor is it necessarily true of consciousness (based on the notion that consciousness is in principle explicable / reducible). The parallels being that we can't check now, the person acts in such a way that the cat/consciousness is/isn't a parsimonious explanation of their behavior, it might be difficult to check, you can fake it (to some degree), you can be wrong about it... and perhaps the cat might be a delusion.
Moreover, some people here claim to have values that encompass things that they cannot in principle interact with in any way (things external to their light cone, for example), so I'm not sure your assertion is unproblematic. If you're going to step on my box, it matters to me whether there's a cat in it, even if you can't check that, and it might in fact matter to you as well. But facts tend to have ripples, so it seems likely that there is, in principle at least, a way to check the catbox.
I encounter many intelligent people (not usually LWers, though) who say that despite our recent scientific advances, human consciousness remains a mystery and currently intractable to science. This is wrong. Empirically distinguishable theories of consciousness have been around for at least 15 years, and the data are beginning to favor some theories over others. For a recent example, see this August 2011 article from Lau & Rosenthal in Trends in Cognitive Sciences, one of my favorite journals. (Review articles, yay!)
Abstract: