gts gts_2000 at yahoo.com
Wed Jan 31 14:53:50 UTC 2007

Gordon: "Say there, Jef! Can you help explain something to me? I don't
know much about probability theory and I was hoping you could help me out."

Gordon: "Let's say I have a coin hidden in my pocket. I retrieved this
coin from my garbage disposal, so I should tell you it might be bent and
unfair, or it might be normal and fair. Are you justified in believing or
assuming it is fair?"

Jef: "What a silly question, Gordon! Of course not! I would need to
inspect your coin or see some other evidence before I would be justified
in commenting in any way about the fairness or unfairness of that coin in
your pocket. Until then I have no justification for believing or assuming
it is fair, and no justification for believing or assuming it is not fair."

Gordon: "Okay, that's what I thought. Just wanted to be sure. Thanks for
the lesson."

Jef: "You're welcome!"

(The ghost of Pierre-Simon Laplace enters the room and taps Jef on the
shoulder)

Laplace: "Excuse me, but I couldn't help overhearing that conversation."

Jef: "Huh? Who are you? Borat?"

Laplace: "No, I am the one-and-only Pierre-Simon Laplace, Magnificent High
Priest of the Glorious Classical School of Probability! I am here to
enlighten you about the Beautiful Principle!"

Jef: "What Beautiful Principle?"

Laplace: "My devoted followers called it the Principle of Insufficient
Reason. You moderns call it the Principle of Indifference. The principle
states that if you have no reason to expect one outcome over another, the
outcomes are equiprobable."

Jef: "Wow! That really IS beautiful! It's BEAUTIFUL and it's ELEGANT, so
it must be a TRUE PRINCIPLE OF LOGIC!"

Laplace: "That's what I thought, too. Good luck with it, Jef. I have to go
now."

(The ghost of Laplace leaves the room.)

Jef: "Say there, Gordon! Come on back here! I have something new to teach
you!"

Gordon: "Great, what is it?"

Jef: "I was wrong before when I said I have no justification for assuming
that coin in your pocket is fair. According to the Beautiful Principle of
Indifference, I am justified in assuming the coin IS fair because I have
no reason to believe it is NOT fair. I heard this from a very reliable
source: Pierre-Simon Laplace!"

Gordon: "Laplace? Reliable? But wasn't he wrong about the determinism
thing?"

Principle, Gordon! Don't you see? It's BEAUTIFUL and it's ELEGANT and it's
TRUE!"

Gordon: "Let me get this straight: a few minutes ago you told me you were
NOT justified in believing or assuming anything about the fairness of the
coin in my pocket, and now you're telling me you ARE justified in assuming
the coin is fair, *despite having obtained no new knowledge about the coin
itself*. Is that right?

Jef: "Right. It's about the Principle, Gordon. It's BEAUTIFUL. You should
be glad I told you about it! You need only dwell on its magnificent beauty
for a few moments, and then you too will have THE POWER."

Gordon: "If you say so..."

-gts