From Rudy Rucker, a riveting essay on "The Bogosity Generator," science fiction's answer to the McGuffin:
Let’s call what I’m talking about a bogosity generator. Kind of like a tank of helium, useful for inflating your pretty balloon animals so they can bobble across the ceiling. Or, more obviously, like an electrical generator that sets the great streams of sparks to arcing across your mad-scientist lab.
The rules are that fantasy authors aren’t expected to justify or to explain their bogosity generators, but an SF writer is expected to cobble together some kind of semi-plausible, paralogical, science-like explanation—that’s considered part of the fun of SF. The styles of these hand-waving explanations change with the intellectual fashions of the times. Over the years, preferred bogosity-generator-justifiers have included radio waves, radioactivity, the subdimensions, relativity, psi powers, black holes, quantum mechanics, parallel worlds, nanotechnology, chaos theory, superintelligent AI, an escalating technological singularity, bioengineering, and our dear friend the Higgs particle.
One point that’s worth making over and over is that an SF writer’s explanations for his or her bogosity generators serve a creative purpose. The theory behind your bogosity generator is not idle bullsh*t. Why? Because in the process of making up the explanation, you get ideas for new things to do with the bogosity generator.