How much of what we call 'reality' is actually out there or rather within our own head?

The distinction between sanity and insanity is narrower than a razor’s edge, sharper than a hound’s tooth, more agile than a mule deer. It is more elusive than the merest phantom. Perhaps it does not even exist; perhaps it is a phantom.

"Do you have information that there's an android in the cast? I'd be glad to help you, and if I were an android would I be glad to help you?" "An android," he said, "doesn't care what happens to another android. That's one of the indications we look for." "Then," Miss Luft said, "you must be an android."

but as he plodded along a vague and almost hallucinatory pall hazed over his mind; he found himself at one point, with no notion of how it could be, a step from an almost certain fatal cliffside fall—falling humiliatingly and helplessly, he thought; on and on, with no one even to witness it. Here there existed no one to record his or anyone else's degradation, and any courage or pride which might manifest itself here at the end would go unmarked: the dead stones, the dust-stricken weeds dry and dying, perceived nothing, recollected nothing, about him or themselves.

Either I've invented a whole new logic or, ahem, I'm not playing with a full deck.

Reality denied comes back to haunt.

How'd you like to gaze at a beer can throughout eternity? It might not be so bad. There'd be nothing to fear.