Angels, Demons, and the Unseen Realm

We’ve seen the bumper sticker, “Don’t drive faster than your guardian angel can fly”. We’ve watched the cartoons where a robed, winged figure with a halo appears on one shoulder to encourage a character to be good and a red, horned figure with a pitchfork appears on the other shoulder to try to influence the same character to be bad. Some of us have even seen the terrifying depictions from Hollywood’s imagination of demonic possession and activity, and the fantastical depictions of angels and the heavenly realm.

But how much of this is fiction, and how much is fact?

When you read the Bible, what does it describe about these beings and what do the individuals who actually encountered them have to say?

What about demons?

Can you see demons or summon them?

Can you do the same with angels? Does everybody have a "guardian angel", or is that just something we made up?