We've talked about how seeing is believing for many people. (Click on the underlined link if you want to review the discussion.) But did you know there's actually a scientific principle that asserts believing is seeing? No really, believe me, there is!
It's most often called the Anthropic Principle, but you can also find it described as observer bias or self-locating belief. Here's the basic idea of the Anthropic Principle:
We believe the information we receive (from our senses, our powers of reason, etc.) is likely true.
We use the information we believe to be true to judge what is likely true about information we haven't yet received.
Afterwards, we're compelled to discount or even completely overlook new information unless we previously judged it to be likely true.
Here's a quick illustration: We receive information about Santa Claus, a portly man-elf with seemingly unlimited resources he graciously shares with those of us who are nice. We believe the information.
(Naughty children, please be forewarned: The naughty do not receive from out of Santa's abundance. It's fair, though. He makes a list; he checks it twice.)
Afterwards, we observe many "Santas" in rapid succession: first in the mall, then outside ringing a Salvation Army donation bell, then on live television landing in a helicopter at the big football game, and so forth. We receive and believe new information that these "Santas" are merely the real Santa's helpers, because the real Santa is extremely busy with various tasks: resource distribution preparations, naughty/nice list maintenance, taste-testing Mrs. Claus' latest batch of cookies, and so forth.
(We now feel a little sorry for those poor saps who believe all those "helper Santas" are the real Santa. I mean, seriously? How could that even be possible, right? People can be so gullible.)
Afterwards, certain naughty children begin circulating vicious rumors about Santa Claus' generosity empire. There are hints that perhaps the "helper Santas" are actually running the entire distribution program. There are suggestions Santa Claus is...um...not real.
(You and I don't believe these naughty children one bit, of course. "Santa is real! Santa is real!" We vigorously shout to the empty, lonely sky. A neighborhood dog barks in the distance.)
I don't like this illustration anymore, readers. I'm pretty sure the same rumor-mongering naughty children who spread lies about Santa Claus grow up to be scientists who invent principles like the Anthropic Principle.