Wicked

"...Do you even believe in other worlds?"

"I find it a great effort to believe in this one," said Sarima, "yet it seems to be here, so why should I trust my skepticism about other worlds? Don't you believe?"

"I tried to, as a child," said Elphie. "I made an effort. The mothy, gormless, indistinct sunrise of salvation world - the Other Land - I couldn't get it, I couldn't focus. Now I just think it's our own lives that are hidden from us. The mystery - who is that person in the mirror - that's shocking and unfathomable enough for me."

Wicked - Gregory Maguire