The Fine Tuning Argument is an Argument for Atheism

08 Dec

So I thought I would attempt to use Bayes’ to see if the Fine Tuning argument was a good argument. The Fine Tuning argument basically says that the universe was fine tuned for life because if the universal constants (like say, for gravity) were any different, then life could not have come about. Since life did come about, the constants must have been consciously picked so that life could arise. Thus a personal god exists.
I think that this argument is fallacious, just to be honest. But I think using Bayes’ will bring about why my objections to it are valid. Hell, maybe the opposite will happen and I’ll be convinced that the fine tuning argument is better than any alternative!
In order to arrange this argument in Bayesian fashion, I need three variables: The prior probability, P(H), the probability of the evidence given the truth of the hypothesis, P(E | H), and the probability of the hypothesis given some other hypothesis, P(E | ~H).
Since what we are trying to prove is that some personal god created the universe, this will be our hypothesis H. Thus P(H) is the prior probability that some personal god created the universe. Said in another way, this is the probability that some personal god created the universe before we decide to look at the evidence of the universe’s supposedly finely tuned constants. Of course, this is an extraordinary claim, so this means that we are dealing with a low prior probability. I think that maybe having a prior of .1 (10%) might be good, especially since I think this is giving way too much leeway; this is a couple of magnitudes higher than the prior probability of winning the lottery.
Next is our P(E | H). What is the probability that the universal constants are what they are given that a personal god created the universe? Let’s grant the opposition their grandest claim, that this is .99. There’s a clue in the nature of P(E | H) that says that this cannot be correct. Why? Because P(E | H) + P(~E | H) has to equal 1.00. So this would mean that P(~E | H) is 0.01, or in plain English, that the proability of not having the constants the way they are given that a personal god created the universe is 0.01!
Of course, here the theist is in a bind. Assuming that a personal god created the universe, what is the probability that the constants would be some other values? Shouldn’t this also be .99? This reasoning sounds a bit familiar… oh yeah, it sounds just like my post something that explains everything explains nothing. It seems to me that given that a personal god created the universe, any sort of physical constants imaginable are possible. Moreover, any single one of these infinite combinations of physical constants could be used to support human life. Assuming otherwise means that there was some standard of what physical constants humans could survive in that this personal god had to go out and look up and then use that formula to create the universe. A lot like if you wanted to make apple pie. So the fine tuning argument actually assumes a god that had to reference what sort of universe humans could live in and was restricted to this meta-human-suitable-universe instructional manual and simply followed the instructions.
That’s not a god anyone believes in!
Assuming traditional theism, the instructions for making human-suitable universes didn’t exist before this personal god existed. Moreover, since the god that most people believe in could simply use perpetual miracles to sustain human life in any sort of combination of universal constants, it seems as though our actual P(E | H) is 0.000…001, with the … representing infinite zeroes for the infinite combination of physical constants so that P(E | H) + P(~E | H), the ~E representing all other possible combinations of universal constants, all adds up to 1.00. I mean at this point, P(E | H) might as well be zero.
Next, I have to figure out what P(E | ~H) is. This is the probability of the universal constants being what they are given that a personal god did not set them. I still have no idea what this would be, but again, let’s grant the theist their argument (since I have nothing else to go on), that this is similar to winning the lottery or something. Let’s make it 0.0000000000001.
We now have our three variables. Let’s work it out:
P(H | E) = P(E | H)*P(H) / [P(E | H)*P(H)] + [P(E | ~H)*P(~H)]
P(H | E) = 0.00…01 * .1 / [0.00…01 * .1] + [0.0000000000001 * .9]
P(H | E) = 0.00…01 / 0.00…01 + 0.0000000000009
P(H | E) = uhhh… pretty close to zero.
That didn’t help!
Remember the likelihood ratio? We basically have zero (0.000…01) divided by 0.000000000001. Or, small number divided by (relatively) large number. Which means that the likelihood ratio is lower than 1. When this happens, it looks like the evidence is actually in favor of the alternative hypothesis. It seems as though the existence of the universe with the constants as they are is actually evidence for atheism. That’s kind of a surprise!
Yes, you heard that right. Not only is the Fine Tuning argument a bad argument for theism, the Fine Tuning argument is actually a somewhat good argument for atheism (in light of this surprise, I think I’ll change the title of this post to something more sensational… heh).


Posted by on December 8, 2011 in Bayes


2 responses to “The Fine Tuning Argument is an Argument for Atheism

  1. Robert

    December 8, 2011 at 5:33 pm

    This is counter-intuitive and could use some peer review. Why not post it at the discussion section? If the argument is sound, it will get more traffic. If not, you will probably discover your mistake.

  2. J. Quinton

    December 9, 2011 at 4:46 pm

    I would like to post it on Less Wrong but I don't have the time these days to keep up the pace with a discussion board (which is why I stopped posting on FRDB). So I don't want to be seen as a hit and run poster for not keeping up with the feedback. I hardly keep up with the posts on here!I think the reason why it seems counterintuitive is because of the contradictory nature of traditional theism. All that I think this post shows is that traditional theism isn't the correct answer for why the universe seems finely tuned; it probably doesn't argue just for atheism, but whatever else (including atheism) is included in ~H. That being said, I think the correct answer is that this is a bogus argument with a false assumption. The universe isn't fine tuned for life, life is fine tuned for the universe. 

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