Babylon 5 was a really stunning sci-fi show in the latter part of the of the 20th century. I'm hoping everyone has seen it by now, cos this page is in someways a bit of a spoiler.
One of the species that featured in the show were called the Vorlons. They were strange mysterious creatures who lived in specially constructed environment suits because they didn't breath the same kind of air as humans. Or at least, that is what they had everyone believe. They were mysterious, enigmatic and seemingly all knowing.
Then one episode was aired that explained who or rather what the Vorlons were. They were Angels. And they weren't Angels. They basically appeared to whoever saw them as whatever that person believed Angels looked like. Replacing the term "Angels" with whatever is the analogous term in that person's religion. What they actually were, was an ancient race who had stayed behind to guide and teach the emerging new races.
This got me thinking. How do you know if what you're talking to is what it appears to be or whether it's a Vorlon pretending? You can't really, it's all down to a matter of trust and belief.
A good example of this happened a few years ago when whilst wandering through a really great park I know, I thought I saw my friends that I'd got seperated from walking some distance away off the path near a lake. I decided rather than heading towards them, I'd meet up with the further along path as that was the direction they were heading anyway. I looked away for a brief moment and when I looked back they were gone. I found them already a good distance ahead instead. Clearly it wasn't my friends I saw, but instead something pretending to lure me towards the lake.
Bad things have no qualms about pretending to be something they're not to trick you into trusting them, but what about good things? I suspect our own views on the world are as much to blame for seeing what we want to see as stuff pretending to be what it isn't.