The late, great Terry Pratchett is one of my favorite authors. In his fantasy universe known as the Discworld (so named because the world is a disc resting on the backs of four giant elephants standing on a turtle swimming through space) he explored nearly every facet of humanity: war, peace, family, crime, politics, time travel, magic, and even religion. A concept running through a number of his books is the notion that believing in something causes it to exist and grow strong.
In Small Gods, a satire on the Reformation, he describes the origin of the gods thus: just as the physical universe was formed of the collation of dust from the origin of the universe, there was a great cloud of gods spread evenly over the universe. As humans believed in a god, it became stronger and better able to answer prayers. Moreover, the gods took on the characteristics of the humans who believed in it — a god of shepherds had a different personality than a god of goatherds, as their followers had different views of how one controls livestock — and the god took its physical characteristics from the sculptures and icons of the followers. e.g. Patina, the goddess of wisdom, was supposed to be associated with an owl; because her most famous sculptor was terrible at sculpting birds, she now has a penguin.
This idea is taken further in Hogfather. There, an assassin takes on the task of killing the Discworld’s version of Santa Claus, not by poisoning his milk or cookies, but treating him as just another god. If a god needs believers, you can kill him — or at least render him impotent and forgotten — by simply convincing people he wasn’t real.
Was the Hogfather a god? Why not? thought Susan. There were sacrifices, after all. All that sherry and pork pie. And he made commandments and rewarded the good and he knew what you were doing. If you believed, nice things happened to you. Sometimes you found him in a grotto [at the mall] and sometimes he was up there in the sky …
In the course of the book, the extra belief freed up by people not believing in the Hogfather allows for the creation of other mythical beings: the bird that eats pencils down to the eraser, or the elephantine eater of socks:
The book concludes that as children we need to believe in the Hogfather to make him real, so that as adults we can believe in things like justice, mercy, and duty to make them real.
So my question to you: what are you believing in, and what intangible things are you making tangible by your belief?