[extropy-chat] Atheism in Decline

[Hal Finney]

> From: ""Hal Finney"" <hal at finney.org>
>
> > I'd suggest applying some of the basic principles of Bayesian reasoning
> > to the question of atheism vs belief in God.  Bayesian reasoning works
> > on the basis of probability.

Olga Bourlin writes:
> There is no reason to use this little exercise regarding 
> [G][g]od(s)[ess][esses] any more than putting magic bean stalks, mermaids, 
> elves, ghosts, pookas and the like through the same Bayesian reasoning.
> Is there?

The point is, Bayesian reasoning should be able to deal with all of these
things, and more.  Many people believe in ghosts.  How about Bigfoot?
How about UFOs?  How about psychic powers?  If you're going to approach
the world rationally, you need to be able to come up with at least a rough
estimate of the probability of all such phenomena.  And that includes God.

Giu1i0 Pri5c0  writes:
> As you say, it depends on the definition og God. If we take the
> definition that most people must have in mind, that God is a being who
> stands outside the universe, created it and can  intervene at will
> (this btw is compatible with a simulation theory), there is no way to
> assign a probability on the basis of available evidence.

And Damien Broderick writes:
> ... I don't think Bayes can help; one 
> would be required to leap outside the system of empirical evidence and 
> recurrence.

I am amazed at the suggestion that there is a potential phenomenon,
one which would cause actual effects in the world where we live, for which
we cannot even in principle ascribe a probability to its existence and
reality.  If true, this is a dagger at the heart of rationality itself,
and calls into question the whole scientific enterprise of studying the
world through observation and reason.

I'd like to understand this suggestion in more detail.  Here's one
theory that I have.  Suppose that we had perfect historical knowledge, as
though we had lived through and witnessed all historical events.  We knew
the historical Jesus, we watched the life of Moses, we grew up with the
Buddha and travelled with Mohammed.  We witnessed the birth of humankind,
either gradually from the animals or stepping fully formed from Eden.

If we had this detailed knowledge, would you still say that it was not
possible in principle to ascribe a probability to the reality of, say,
the God of the Christian Bible?  What I'm getting at is the question
of whether you see the reason for the difficulty in applying Bayesian
reasoning as simple ignorance of historical facts.  You both mention the
difficulty of using "evidence", and I'm wondering whether the problem
is primarily the relative paucity of the evidence we have to go on.

Another theory I can imagine in trying to understand this claim is that
the problem is with the idea of probability as something that applies
only to repeatable events, based on Damien's mention of "recurrence".
When we say that the probability of a flipped coin coming up heads is 50%,
we mean that we can flip the coin many times, and on the average about 50%
of them will be heads.  But we can't do this with the universe.  We can't
really imagine a whole ensemble of actually existing universes, some
where God exists and some where he doesn't, and then ask what percentage
of them have God existing.  That seems to be an absurd cosmology, because
if God created some of the universes he would probably have created all
of them; and contrariwise, if actual universes could exist without God
creating them, then there seems little need to postulate the existence
of God at all.

If this is the problem with trying to give a probability for God's
existence, I would point out that there are other notions of probability
which don't rely on repeatable events.  We create probability estimates
all the time for non-repeatable events.  In a sense, every event is
unique, but that doesn't stop us from estimating likelihoods.

The way I think about probabilities like this is that we estimate the
strength of our belief, and we calibrate it by comparison with beliefs
regarding events which actually are repeatable.  What are the chances
that Hillary Clinton will be elected President in 2008?  I'd say...
one in five.  There is a better than even chance that a Democrat will be
elected, after 8 years of Republican fatigue, and Hillary is a prominent
Democrat who might well run.  I compare my belief in this one-time event
with how strongly I believe that I will get heads on my next two coin
flips, and judge Hillary's chances as being a little less than that.

Another way to think of it is, of all the beliefs that I have to
which I would ascribe one-in-five probability, both reproduceable and
non-reproduceable events, I expect about one in five of them to come true.
So even non-reproduceable events can be seen as part of an ensemble where
we can use a frequentist notion of probability to calibrate our beliefs.

>From this perspective, the existence of (some particular conception
of) God, like the existence of fairies, ghosts, mermaids and other
supernatural creatures, can be given a probability estimate despite its
superficially unique nature.  No actual recurrence is necessary.

I'd like to know whether either of these lines of argument shed light
on the question of why we cannot ascribe a probability to the existence
of God.

Hal