Theories are essentially ideas that need yet to be proven, or at least, they are proven when enough evidence is shown to make them look true. Very rarely, a theory is entirely correct, unless it's very simple.So then, if that's true, then I say this: no idea is entirely true. Somewhere, there's a untruth. Even in what I am saying now, someone can show me why it's wrong. My point is, maybe, whenever we talk, we invent new theories, or put new spins on ones that were presented to us just before.
Basically, when I say "David just left quickly to the supermarket.", this is what I believe. There is a slight possibility that I was hallucinating, that David did not in fact leave. Therefore, it's a theory. Then, when someone else says "He also took my twenty dollars strait out of my pocket!", this can be argued against with the very fact that David may not have taken the twenty, it's possible it wasn't a twenty, that he took it out of the person's hand, instead.
Even if David were to uphold these claims, then there would be the problem that he too could have been hallucinating... The possibilities are endless to this argument.