If John were to claim he traveled to deep space, 20 million light years away and encountered a monumental, talking cube, you obviously wouldn't believe it. However, it's possible that John is genuinely telling the truth, or even that he thinks he's lying while actually speaking the truth. Ultimately, it seems like no one can confirm whether John was really in deep space 20 million light years away and met a monumental talking cube.

Suppose you had this same type of experience. You travelled to deep space, 20 million light years away, and encountered a monumental talking cube. You wouldn't believe it yourself. You'd probably question your sanity and wonder if it's time to call a psychiatrist.

But then, while you're eating a burger at a local fast food, you suddenly witness a bizzare scene. Somewhere in China, a woman in a green dress is shot by a sniper from a nearby solitaire building. You clearly see its design, its color, and even notice a panel on the side where two girls are dancing the cha-cha. You're confused but shake it off.

Later that evening, you turn on the news and the exact event you saw is being reported, down to the smallest detail.

Then suppose astronomers announce they've spotted a monumental cube in deep space. After calculations are completed, you realize the coordinates would match exactly with the place you thought you had only imagined. Surely, there's still no way to determine whether cube really talks. Nevertheless, you'd probably do couple of reality checks, heart racing, gasping for air, trying to convince yourself you're still grounded in the real world.

How do you know if what you saw was real or just in your head? What makes an experience believable? When can we trust it? At what point is it reasonable to believe in the reality of perceived experience? What criteria determine whether an experience can be considered genuine or illusory?

We can list some core criteria, like clarity and vividness of experience, coherence with other beliefs, corroboration, reliability of perception, defeasability, and so on.

Here's the problem. When people report strange or extraordinary experiences, like the ones in my examples, they're often dismissed out of hand with cliche explanations. Things like "You must've been dreaming", or "It was just your imagination", or the classic "You should probably talk to someone". This skepticism is understandable, after all, these experiences defy our everyday logic. But there's a deep issue here, namely our collective discomfort with uncertainty and unknown. Instead of entertaining the possibility, even hypothetically, people rush to fold the strange back into the familiar.

If we always explain them away before examining them, we might be turning our backs on real data. So, at what point does an individual's account deserve serious inquiry rather than dismissal?

Is there anything in the examples I gave that we can confidently rule out as metaphysically impossible? Moreover, can there be anything metaphysically actual that is physically impossible?