Rarity As Evidence

This essay is about how and why people incorrectly use the rarity of something as evidence to an unrelated claim.

Often times in a debate people will quote extremely rare odds (like a billion-to-one) in order to give evidence to help prove their claim. This should be avoided because rarity proves only that something is rare.

For example, assume there is a pile of a billion cards in front of you. Each card has a number on it from one to a billion. The cards are all shuffled together to assure they are random. Now you must draw one, and only one, of those cards.

Okay, so we have our billion cards and your about to pick one, but before you do, you bet a hundred dollars that you will draw card number 12 from the pile. You reach into the pile and pull a card and lo and behold you draw card number 12. Everybody watching would be in disbelief. How could you have drawn that card, the odds were a billion-to-one! Everyone is led to the conclusion that you have cheated, the cards were marked, somehow you knew you were going to draw number 12. No matter what, nobody will believe that it was merely a random chance that you drew card number 12.

Do you see the problem with that?

People find the odds of a billion-to-one so rare to beat they automatically conclude that you have cheated. However, just because you pulled the right card doesn't prove that you have cheated. There could be any number of other possibilities for you pulling that number. The only thing that should be used as evidence of cheating should be actual evidence of cheating.

Okay let's state the same scenario but in a different manner. We have our pile of cards and you're going to pick one out. No bets or predictions are made. You reach into the pile and pull out card number 306,293,881. Nobody stares in disbelief, nobody claims that you have cheated, nobody bats an eye. Why not? The odds of you pulling card number 306,293,881 are exactly the same as pulling card number 12. Why do people think you cheated in the first scenario, but the second was okay?

The difference comes from what is expected. In the first scenario everyone blindly expects a certain outcome, but in the second scenario any outcome will do. Because in the first example the outcome was not what was expected, people jump to conclusions without even taking the time to evaluate the evidence properly.

This doesn't mean that you should assume that every result that beats extremely rare odds is genuine. In fact, beating extremely rare odds is a good indication that the test was done improperly and in need of further evaluation. What this does show is that you shouldn't attribute the rarity of something as evidence to something else. Now if we assume that the first scenario was video recorded, and that upon watching the recording we see that you had a bulge in your sleeve the same size as the cards before you reached your hand into the pile. Now we would have some evidence for cheating.

Extremely rare events happen all the time, think how often someone wins the lottery, but we don't claim that every person who won was a cheater.

A good example of how rarity is misused as evidence comes from the creationist's argument. This essay isn't meant to prove or disprove creationism, it is merely showing how creationists often misuse rarity as evidence.

Obviously, our planet is capable of supporting life. It's ability to support life comes from a combination of its size, rotation, tilt, orbit, distance from the sun, and the solar system's position in the galaxy, among many other factors. The odds of getting another planet with the exact same conditions are astronomical. Trillions and trillions to one. Because of this, many creationist are led to believe that because the odds are so rare, that our universe must have been created, and not just a random event.

Do you see it now?

There could be any number of various other possibilities for the Earth being setup the way it is. Just because it's rare doesn't prove creation. The only thing that should be used as evidence for creation is actual evidence for creation.

Rarity only proves one thing. That it is rare. Evidence for any other claim must be found to support the claim. Rarity is not evidence.