“So what’s the point of showing me something I can’t see?”
“So that you understand that just because you see something, it doesn’t mean to say it’s there. And if you don’t see something, it doesn’t mean to say it’s not there. It’s only what your senses bring to your attention.”

Douglas Adams (1952-2001) English author, humorist, screenwriter

Hitchhiker’s Guide No. 5, Mostly Harmless, ch. 17 (1992)
    (Source)

Random and the bird Guide.