* “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.

]]>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.

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