# MATH: Weird probability arguments

Twirlip of Greymist (phoenix@ugcs.caltech.edu)
Thu, 5 Dec 1996 17:16:36 -0800 (PST)

On Dec 5, 11:53am, Hal Finney wrote:

All people make sense, I tell myself. If you know their values (which
may be inconsistent) and their perceptions (which may be 'flawed') then
you know them. So I tell myself. In fact, empathy may be much easier
with different or even inconsistent values than with different
perceptive systems and filters...

} "doomsday argument" at length. This is the idea that if the human race is
} actually going to expand through the galaxy and become much more populous
} in the future, the chances are remote that we should find ourselves so
} early in its history when such a small fraction of the race has lived.

...e.g. I find this argument utterly bizarre. Whether 21st century
humanity dies out or goes on to Omega, to reach the 21st century someone
had to live in the 20th. That happens to be us. If someone else lived
now, "we" wouldn't live later on; "we" are those who live here and now,
who have grown up in this century.

When contemplating any future with a history, given that the future will
happen the probability of the history having happened is 1.

} the point it was created, within a few decades of the year 2000. Hence
} the fact that we are living through this moment is unsurprising since

So what about the 19th century? Or the 5th B.C.? Someone lived through
those moments. Should Babbage have commented on how unlikely it was for
him to have existed?

I'm not sure about the dice. Every instinct says that the probability
is always 1/36, but I haven't figured out how to refute the 90% argument
in the past couple of minutes.

Merry part,
-xx- Damien R. Sullivan X-) <*> http://www.ugcs.caltech.edu/~phoenix

"Perhaps you are thinking: "But a tank costs several million dollars,
not including floor mats. I don't have that kind of money."
Don't be silly. You're a consumer, right? You have credit cards, right?
Perhaps you are thinking: "Yes, but how am I going to pay the credit-card
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