More on Fine-Tuning & the Multiverse

comments 14

I’ve thought of a simpler way of making the argument from my last post. Suppose Jack is the defendant, and the lawyer for the prosecution shares with the jury that Jack carries a knife around with him. In fact, as the lawyer for the prosecution well knows, Jack carries a butter knife around with him, but the lawyer chooses not to share this detail. Obviously the jury are going to be misled. It’s not that they’ve been told a lie: it’s true that Jack carries a knife around with him. The lawyer has misled the jury by giving them a less ‘filled in’ account of the evidence than is available.

This example (modified from an example due to Paul Draper) reveals a very important principle in probabilistic reasoning, a principle I would define as follows:

The Requirement of Total Evidence (RTE) – Never bypass the evidential implications of specific evidence in order to focus on weaker evidence.

(That ‘Jack goes around with a knife’ is weaker evidence than ‘Jack goes around with a butter knife’ because the latter entails the former but not vice versa).

It is this principle that is violated by those inferring a multiverse from the fine-tuning. The evidence that our universe is fine-tuned is striking to us because it raises the probability of something god-ish: simulation hypothesis, Nagel-style teleological laws, cosmopsychism, etc (I would not go for the omni-God, as the existence of suffering is powerful evidence against the omni-God). However, our culture tells us that god-ish hypotheses are ridiculous. And so, in general, those scientists who do find something compelling about fine-tuning bypass the god-ish evidential implications of ‘our universe is fine-tuned’ in order to focus on the weaker evidence that ‘a universe is fine-tuned.’ This is in violation of RTE and hence is a fallacious inference.

It’s exactly the same error we find in the classic Inverse Gambler’s Fallacy (IGF) case:

You walk into a casino and see someone roll all sixes with twenty dice. You infer that there must be lots of people playing in the casino tonight, as it’s more likely that someone will make such an incredible roll if there are many players.

The problem in this case is that the evidential implications of the specific evidence that ‘this roll was a double six’ (such an extraordinary roll raises the probability that the dice are loaded) are bypassed in order to assess the probability of the weaker evidence that ‘someone the casino rolled all sixes with twenty dice.’

It is commonly pointed out that there is a selection effect in the fine-tuning case which isn’t present in the casino case: we couldn’t have observed a universe that wasn’t life-conducive but we could have observed someone making a terrible roll. In my last post, I sketched the Jane analogy which has a selection effect but is still fallacious. However, a more direct response is to point out that the presence of absence of a selection effect has no relevance to the explanation of why the casino example is fallacious (which is that the reasoner bypasses specific evidence to focus on weaker evidence) and hence does nothing to block the multiverse inference being fallacious in the same way (as this inference also involves bypassing specific evidence to focus on weaker evidence).

If the multiverse theorist wants to resist this argument, they not only have to deal with the Jane analogy from my last post, but they also need to explain why the inference to the multiverse is exempt from RTE. I’ve seen some attempts at the former (although none I’m as yet convinced by) but I haven’t seen any attempts at the latter.

[I should credit a tweet from Thomas Metcalf with making me think that maybe we can simply modify our understanding of RTE rather than qualifying it, although I don’t quite agree with his way of doing that, which I hope to talk about in future work. This has been a ‘Eureka’ moment in my thinking on this. In his original article on this, White appealed to RTE, but I was mistakenly thinking it entailed we always have to focus on the strongest evidence we have, which is obviously false, and so I thought White must have got the theoretical underpinnings of his argument wrong (in a postscript to a re-published version of the paper, White gave up on RTE and offered instead a new theoretical justification, which I don’t agree with). But now I see that we can make the argument in terms of RTE, so long as we define it as I do above. Finally, for those following these Twitter discussions, I should also confess that I haven’t yet got around to reading Quentin Ruyant’s second response to me.]

The Author

I am a philosopher and consciousness researcher at Durham University, UK. My research focuses on how to integrate consciousness into our scientific worldview.


  1. Pingback: More on Fine-Tuning & the Multiverse – Conscience and Consciousness - Nobodys word

  2. Stephen Davies says

    I walk in and see someone roll 20 6s. I wouldn’t think that this is evidence of the dice being loaded. I equally wouldn’t think it is evidence of there being many people rolling simultaneously. If the roller was celebrating getting 20 6s, I might wonder if she had been trying for some time and had many ‘failed’ rolls before.

    If there are many worlds being created with varying ‘fine-tuning’ numbers, then it isn’t so surprising if eventually one creates life. Why does many-worlds theory have to equate with other rollers in your analogy, rather than many rolls?

    Why are loaded dice only analogous to a creator? Why can’t they be an analogy for physical laws being loaded towards fine-tuning constants?

    Why is the supposition of loaded dice stronger evidence than the supposition of many tries?

    (I have no desire to avoid better evidence for weaker evidence as I happen to think a consciousness-based virtual reality is the answer.)

  3. On your first point: I’m surprised to hear you don’t think that’s evidence for the dice being loaded. What if they rolled a hundred dice and got all 6s? What if they rolled all day and got sixes every time? Surely we would conclude the dice were loaded?

    The point is that it’s fallacious to take our evidence to be ‘*a* universe is fine-tuned’ just as it’s fallacious in the casino case to take our evidence to be ‘*someone* rolled double six’. In both cases, you’re bypassing stronger evidence to focus on weaker evidence. And once we (correctly) focus on ‘*this* universe is fine-tuned’, the multiverse is not supported, as the existence of other universe has no bearing on the likelihood of *this* universe being fine-tuned.

    There could be teleological laws disposed the universe towards life (that’s one of the ‘god-ish’ options I’m open to). But if you’re just suggesting non-teleological laws that happen to dispose the universe to the life, that’s just another chance hypothesis, and you’re gonna get a solid Bayesian argument for something god-ish over that chance hypothesis.

    On your final point, you’re talking there about hypotheses not evidence (see my second paragraph above).

    • Stephen Davies says

      ‘I’m surprised to hear you don’t think that’s evidence for the dice being loaded.‘

      Because I know that that roll has exactly the same chance of happening as any other.
      (And I would very much expect that a casino would not have loaded dice 🙂

      Did you read my Derren Brown lottery example in your original post, it relates to my other comment here of a creator using a many-worlds method.

      Thanks for taking the time to read and reply 🙂 I appreciate your efforts in reaching out to the general enthusiast.

    • Stephen Davies says

      If the dice were loaded (or the laws were teleological) I would think that they would be more likely to roll the 6s in less attempts, but I have no evidence of how many rolls if any have taken place before so no evidence to say either way.

  4. Stephen Davies says

    If there was a creator, they could have used a random many-worlds method to create the world. They might not have known what the constants for life were.

    Do we have weaker evidence for this method than for them knowing the constants?

    And do we have weaker evidence for physical laws being a many-worlds method than a creator using a many-worlds method?

    • On whether we should think the dice loaded: it’s not about how improbable the roll is. It’s whether there’s some non-ad hoc hypothesis (e.g. the dice being loaded) that renders the data more probable than on a chance hypothesis. Check out the analysis of ‘surprising’ in my last post on this.

      • Stephen Davies says

        Then every and any roll you ever observed you would think the dice were loaded to whatever each outcome was!?

      • No, because it’s not the case for every roll that there’s a non ad hoc hypothesis that would make it likely that you’d get that roll. Perhaps the point is easier in the lottery case. If some random person wins the lottery, there’s no reason to think there’s cheating. But if the partner of the lottery wins, there is, because there’s a non ad hoc hypothesis (namely that it was rigged) that makes the result much more likely that chance. Same in the dice case.

      • Stephen Davies says

        I wonder if the analogies being used are creating as many problems as they are solving 🙂

      • These aren’t just analogies but theoretical explanations of what’s going on in probabilistic reasoning.

  5. First Cause says


    I don’t know if you can appreciate that your entire argument is an a priori analysis where “all of the arguments” for or against a fine-tuned universe are contained within the original proposition. The same thing is true for an argument for or against the existence of God.

    However, if one employs a synthetic a priori approach, then all of the arguments for or against will not already be contained within the original proposition. Unlike a priori analysis, synthetic judgments add something to a concept that is not already contained within the original proposition, whereas a priori analytic judgments only explain what is already contained in that concept.

    For example: if one understands the concept underwriting synthetic judgements, it can be definitively “proven” beyond any reasonable doubt that God does not exist. I do not observe you or any of your academic colleagues employing synthetic judgements in your dialectic arguments, and that is why
    all of those arguments are circular, no consensus can be reached and ultimately, all of those arguments reduce to absurdity.

  6. Bob Kentridge says

    IANAP (I am not a philosopher) and IANAS (I am not a statistician) but here is a shot at understanding this in a slightly different way from Philip.

    You see someone roll 20 double sixes in a row and that is all you know about the casino. p(20 double sixes in a row) = 7.48 x 10^-32. Best assume that those specific dice are loaded.

    You are told that *someone* rolled 20 double sixes in a row and notice that there are over a million million million million million million people in the room (10^36) – no need to assume loaded dice.

    You see someone rolled 20 double sixes in a row and notice that there are over a million million million million million million people in the room (10^36). Safest to assume that the dice you see are loaded, but also accept that this conclusion might be wrong as you must also accept that sequences of 20 double sixes are occurring elsewhere from unloaded dice.

    So, if we accept that there are an infinite number of multiverses isn’t it irrelevant that we’ve seen fine tuning in our universe. Don’t we just have to accept that fine tuning will occur. We don’t have sufficient evidence to know whether the fine tuning in our universe is down to god (loaded dice) or chance (but a chance that is bound to occur in an infinite number of universes)? The multiverse *can* explain fine tuning, but it does not necessarily explain fine tuning in our universe.

    • Thanks Bob! I agree with your response to your first two cases. On the third, I think it’d depend how you came to see the incredible roll. If you randomly sampled one, and got an incredible roll, I think that’d be good evidence that in general the dice are loaded. But coming to the real world, I agree that if we had incredibly strong evidence that we were in a multiverse *of the right kind*, i.e. where the % of fine-tuned universes is what you’d expect on chance, that would totally undermine the fine-tuning argument for something god-ish. The reality is, though, that we don’t have evidence for anything like that. We arguably have speculative evidence for some kind of multiverse, and theoretical grounds for taking seriously the possibility that the constants vary in different universes. But if we going to go for a multiverse hypothesis, we should go for one that renders probable our evidence that our universe is fine-tuned, i.e., a multiverse hypothesis in which some god-ish hypothesis ensures that all or a large % are fine-tuned.

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