B.C.
Why do grown ups make this so difficult?
Facts and belief have very little to do with each other.
My son's 11 soon to be 12. He's never asked about Santa, but he knows and still has no trouble believing at the same time.
Suspend disbelief - literally "stop not believing".
Where do we lose it? Why do we have to lose it?
The world is too mundane without imagination.