Teuton wrote:

Will S wrote:Of course, I know that the Fine Tuning argument can be attacked in other ways too, but I'm especially interested in the statement about probability.

Then you'll probably find the following paper interesting:

http://homepage.mac.com/mcolyvan/papers/finetuning.pdf

"Abstract: The argument from fine tuning is supposed to establish the existence of God from the fact that the evolution of carbon-based life requires the laws of physics and the boundary conditions of the universe to be more or less as they are. We demonstrate that this argument fails. In particular, we focus on problems associated with the role probabilities play in the argument. We show that, even granting the fine tuning of the universe, it does not follow that the universe is improbable, thus no explanation of the fine tuning, theistic or otherwise, is required."

Thanks for the reference. It's an interesting paper, even if (as is common with such papers!) it sometimes reminds me of a very large elephant laboriously picking up very small pins.

To summarise a few points which I've gleaned from the discussion so far:

1 The physics of a universe which supports life, even life like ours, isn't unique. The Harnik paper shows quite nicely that you can dispense with the weak force, make a few other adjustments, and still end up with a universe quite like ours

2 This raises the question of how "probable" a life-supporting universe is, but even asking this question raises a big clump of additional questions:

2a What is the "sample space" of universes we're going to ask this probability question about ? Is it ones with something like our standard model, but you just look at all possible combinations of the physical constants in the model ? Is it ones were you can vary "deeper" things like the number of dimensions ?

2b How do you define a probability measure on this sample space of universes ?

2c Is there some "meta law" which controls the probability distribution used for sampling ?

3 How do we know our universe isn't a simulation ?

4 Now I remember why I didn't want to do philosophy

^^ I have always wondered why we can't think of the possible universes as a continuum, with an infinite number of possible configurations between every other two possible configurations.

The "probability" question presupposes too many things to be answered at the present time. To make the least assumptions you have to say that we have evidence for this universe and no compelling evidence that other universes exist or could exist. Therefore the probability of the current set of constants is simply 1 until new evidence comes to light.