Saturday, October 06, 2007

Making sure your god has little chance of being true

Here's Sam Harris' speech last September at the Atheist Alliance International convention in Washington DC.

I found myself wildly agreeing with a good number of things he touched upon, although I think his suggestion to stop calling ourselves atheists is a pipe dream, even as I agree with his reasons. Moreover, I was happy that he clarified and explained his continuing interest in spirituality and meditation. He has made some valid points. Be that as it may I still have my reservations. Meditation I can still buy (cautiously), but until someone can tell me what spiritual/spirituality really is, for me it'll remain in the bunk department.

I'm ecstatic that Harris pointed out a mathematical fact which I had also used in an online debate with a Christian (a Calvinist I believe) last year. It has to do with probabilities for claims. Simply put, the more you specify the particulars of an event, i.e., the more details you enumerate, the less probable that event is.

Let me illustrate. Let's say we're told that a coin has been flipped. The probability that it lands heads is, of course, 50%. But the probability that it lands heads and that the coin flipped is an American coin must of course be less than 50%. This is because in the set of all possible coins there are non Americans ones and so the probability that a coin is American is less than 100%. Multiplying that with 50% yields a value less than 50%.

If we specify more details we will drive the probability further down: The probability that a coin lands heads and is an American coin and is a quarter must be smaller still than the former probability. Hence, the more specifics we enumerate the smaller the probability. (This is one reason why those wishing to go into the psychic trade should provide their audience very general claims and mention as few details as possible.)

So Harris rightly tells us:
[T]he Mormons think Jesus is going to return to earth and administer his Thousand years of Peace, at least part of the time, from the state of Missouri. Why does this make Mormonism less likely to be true than Christianity? Because whatever probability you assign to Jesus’ coming back, you have to assign a lesser probability to his coming back and keeping a summer home in Jackson County, Missouri.

Now compare these two claims:

1. One or more deities exist.

2. There is only one god and he's omniscient and omnipotent and omnipresent and omnibenevolent and composed of three (duh!) persons and he murdered the first-borns of Egypt and flooded the entire earth and incarnated and was born of a virgin and performed miracles and resurrected and will come back to earth and judge humans and commanded A and B and C and D and ... and had done Q and R and S and T and ..., et cetera.

Are you grimacing and wondering why Christians seem to enjoy whittling the probability down to an infinitesimal value?

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