A recent post by P. Z. Meyers mentions, among other things, Pascal's Wager. There are a number of standard replies, which the Wikipedia article mentions. The following reply applies to a fairly general version of Pascal's Wager, in which we assume that belief without evidence has some cost but it's outweighed by the negatively infinite cost of disbelief.
It is possible that there is an army of invisible dragons on the far side of the Moon that are preparing to mount an attack that will lead to the extinction of humanity. These are highly technologically advanced dragons, which is why we have not detected their existence. Plus they are invisible. Now if the invisible dragon army exists, we had better pour all of our social resources into mounting a massive thermonuclear assault on the far side of the Moon, because if we don't get them before they get us, we are all going to go extinct. Clearly, there are four distinct possibilities:
- The dragons do not exist, and we do not believe in them. In this case, OK, we pretty much go about our lives as we do now.
- The dragons do not exist, and we believe in them. In this case, we waste some societal resources in nuking the Moon, but at least we get to survive.
- The dragons exist, and we believe in them. In this case, yay! We nuke the dragons and we get to survive.
- The dragons exist, and we do not believe in them. Holy crap, now we are in some deep shit, because when the dragons attack, we are all doomed, doomed!
This is, you will note, basically isomorphic to Pascal's Wager. Now, if you look at these four possibilities, you would conclude that we had best get started nuking the dark side of the moon, post haste.
Except --- holy shit --- what if the evil army of invisible dragons is actually on Mars, and the dark side of the Moon is, in fact, populated by twinkly Tinkerbell fairies whose magical fairy dust is the only weapon that can kill an invisible dragon! After all, these dragons are magical --- they already live on the dark side of the Moon, and a massive wave of high-intensity radiation may just bounce off their hide. Now we are into some deeply heavy shit, because having bought into our former analysis, we are investing major social resources in nuking the Moon, but if we nuke the Moon we are all doomed because the fairies will all be vaporized. And holy cow, how do we know that the fairies are on the Moon, and the dragons are on Mars? What if the dragons are on the Moon, and the fairies are on Mars? Now we've got a head-spinning vortex of possibilities:
- The fairies exist on the dark side of the Moon, the dragons exist on Mars, and we believe in them. In this case, we send some fairy-harvesters to the Moon to gather up all the fairy dust, plus we need to build some fairy-dust-crop-dusters that can function in the Martian atmosphere. We dust the dragons and yay! We survive!
- The fairies do not exist, but the dragons do exist; but the dragons live on Mars, and not the Moon, and we choose not to believe in any of it. Now the dragons are going to come get us, and we are all doomed, doomed!
- The fairies exist, and they live on Mars, but the dragons do not, but we believe that the dragons exist and the fairies do not. In this case, we will probably nuke the Moon, but the fairies live on Mars, so no harm no foul. Plus we didn't even need the fairies to begin with, since the dragons do not exist.
- The fairies exist, and they live on Mars, and the dragons live on the Moon, but we believe only in the dragons and not the fairies. In this case, we will end up nuking the moon; but --- damn! --- we still die, because we do not realize that the only way to defeat the dragons would be to mount a Mars mission to gather magical fairy dust.
- The fairies live on the Moon, the dragons live on Mars, and ---
Wait a second. What if the dwarves who have lived underground in Caucasus Mountains since the dawn of time could forge us an enchanted sword, with which our chosen champion could command the dragons? In that case, we had better pour all of our resources into invading the Caucasus Mountains and contacting the dwarves, before some random terrorist stumbles upon the hidden cave entrance and says the Word of Power that unlocks the gate that has been shut for countless millennia. Because if some terrorist stumbles on the hidden cave entrance and speaks the Word of Power, we are all fucked. Plus, we need to maintain military hegemony over the world indefinitely, and if we could command the invisible dragons, we would basically have military hegemony sewn up.
Man, I never knew that computing a simple wager would be so difficult. I'm beginning to lose track. I mean you've got the dragons and the fairies and the dwarves, and holy shit what about the starfaring guild of alien wizards? What about the Ancient and Venerated Order of Elephant Shamans? What about the Conspiracy of Snowboarding Yetis? What about the Creeping Evil from Beyond Space and Time? This matrix of possibilities is growing exponentially with every sentence. But basically, the point is, in most cases, you're better off believing that everything exists, because what if it does? HMMMMMM? WHAT IF IT DOES EXIST? Then we are all FUCKED. So believe, motherfucker, believe, before the Teddy Bear Von Neumann Probe From Alpha Centauri turns the entire solar system into a bazillion cute and cuddly polyester toys.