The Boundaries

I understand that in the world, there is a line, a definite line. Real, Unreal.
This is the core of how we interact and experience life. There are some where this 'line' is disillusioned and misconstrued. We treat them in our prisons and in our mental facilities, mostly.
Now lets think about you, surely a sane minded, down to earth and sure of what they know person. But, what if i could make you think differently?
What happened if something thoroughly impossible in your opinion, happened in front of your very eyes? I'm not speaking about illusion and magic, but maybe I should.