## Interesting discussion in progress at The Secular Outpost

May 9, 2014 by lukebarnes

Thanks to GGDFan777 for the tip-off: Jeffery Jay Lowder has weighed in on my posts (one, two, three, four) about Richard Carrier. It’s in the comments of this post over at The Secular Outpost. Keith Parsons even drops in with a few comments. [Edit:] More details here: The Carrier-Barnes Exchange on Fine-Tuning.

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on June 5, 2014 at 3:11 am |unkleEHi Luke, I am an interested layperson with only 2 years of undergraduate maths & physics, so the deeper points of all this are often beyond me. My interest (in this comment/question) is in the science, not the theistic argument.

1. Parsons, Lowder, Carrier, et al, make much of probability and how we can possibly calculate it for the fine-tuning of the universe. But I note your formulation of fine-tuning is something like “of all possible universes allowed by theoretical physics, only a very small subset permit life” – which doesn’t mention probability.

Obviously the simple assumption is that the probability function of all possible universes is constant, and this is the assumption that these guys often question. But it seems that the probabilities would have to be enormously non linear to change the conclusion.

How would you respond to that?

2. One interesting feature of your ARCHIV paper is the discussion of alternative laws (not just numbers). You have shown how fine-tuning is justified by the numbers, but it is less clear (to me) that considering different laws still leads to fine-tuning. You discuss 6 cases, but presumably there could be almost infinite ways laws could be varied.

As I have read your discussion, your answer seems to be that if all the universes we have examined point to fine tuning, it is unlikely that things will change just over the horizon. But if what is over the horizon is a much larger sample spaced than what we know, I have seen people argue that makes fine-tuning unwarranted speculation.

Does fine-tuning stand up if we consider all possible laws and not just all possible numbers?

Thanks.

on June 11, 2014 at 1:51 pm |lukebarnes* “doesn’t mention probability” – It’s there implicitly in the phrase “very small”. This can only refer to a probability.

* “Probability function is constant” – the problem is that if the range of the variable is infinite, then this probability function is non-normalisable i.e. I can’t make it sum to one.

* “probabilities would have to be enormously non linear to change the conclusion.” Yep. See page 23 of my arxiv paper.

* Just over the horizon: to be rational is to do the best you can with the information you’ve got. If you can’t reach a conclusion because there are things you don’t know, then you can never reach any conclusion. A larger sample space, in and of itself, doesn’t necessarily negate fine-tuning. One must show that life-permitting universes are common in that space.

One can either follow the evidence that we know, or speculate that everything we know will be overturned by what we don’t know. I think the first option is preferable.

on June 17, 2014 at 11:17 amArkenatenDo you credit a deity/ divine force for Fine Tuning or do you lean toward another explanation?

on June 12, 2014 at 7:32 am |unkleEThanks for taking the trouble to explain that. I had forgotten the argument on page 23, so thanks for the reminder. I guess that probability is implicit in your statement, but it isn’t numerical, which is what I was thinking. Thanks again. I always enjoy your blog.