To follow on from my previous post, Philip Goff has now released a preview of an academic paper in progress on this topic. Currently titled "Is the Fine-Tuning Evidence for a Multiverse?", this paper is a defence of the very same Roger White paper I had been critiquing, and the main argument it tackles relates to some points I made.
I thought I should give my take, but before I do I'll note that I'm not sure if the paper preview link may become stale at some future date or if the paper may be revised in ways that make my comments obsolete. In any case, if you're interested, you should read the paper and my previous post if you haven't already.
Overview of Goff's paper
I like the paper very much, in that Goff is as usual very good at explaining the issues involved and contributes a cogent and interesting argument to the understanding of this problem. His thinking seems reasonable and clear to me even though he starts out with very different initial commitments and so reaches different conclusions.
It's interesting to me how different our starting assumptions are. Generally, the pattern seems to be that I reject the meaningfulness or reality of a lot of intuitive concepts that Goff accepts, among them qualia, objective morality and the essential identity of people and things. I suspect this pattern may continue with concepts such as objective existence, objective aesthetic value etc. In Goff's book Galileo's Error, I was impressed by his arguments for panpsychism, but only if one is committed to the reality of qualia and the necessity of a substantive solution to Chalmers' Hard Problem of consciousness. In this paper, Goff's commitment to the notion of essential identity leads him to support White's argument against inferring a multiverse from fine tuning.
The main contribution of the paper is to address one particular criticism of White's paper presented in this paper by Neil Manson and Michael Thrush. This objection appears to be similar to one I raised in my last post, namely that it's questionable to identify this universe in a way independent of its laws. What I said was:
The idea that this universe could have had other laws of physics is also nonsense, as then it wouldn't have been this universe.
Manson & Thrush don't put it so strongly, arguing only that
there is no agreed account of the nature and identity conditions of a universe
where "identity conditions" in this context refers more or less to what criteria need to be met for this universe to remain the same universe (i.e. this universe) in counter-factual scenarios and over time. Manson & Thrush argue for caution, suggesting that White is mistaken in taking for granted that it is sensible to treat the identity of the universe in the way he does.
Goff proposes that we can do better than just shrugging our shoulders. We can make some inferences about what identity conditions might hold by looking at the physics of the most plausible multiverse scenario suggested by anthropic fine-tuning. This is the combination of eternal inflation with string theory, where each bubble universe is taken to have a random configuration of the laws of physics allowed by string theory. Goff refers to this scenario as Landscape Eternal Inflation (LEI).
Goff argues convincingly that there is little or no empirical reason to suppose that LEI is true other than (some say) fine-tuning. While there is some empirical support for an eternal inflation multiverse, there is no empirical support for the notion that each bubble universe has different laws of physics, as required by LEI. Whether we should give LEI any credence therefore depends almost solely on whether the most plausible identity conditions (what makes this universe this universe as opposed to some other) support White's argument or fine-tuning.
Manson & Thrush suggest that the most appropriate identity conditions could conceivably be what they call "Cosmic Essence", which is similar to my own view of identity (though possibly not exactly so, as we'll see). In this view, what identifies a universe is its laws of physics. It doesn't make sense to ask "what if this universe's laws of physics were different?" because then it wouldn't be this universe! It would make as much sense to ask "what if five were even?" You can't make five even and have it still be five. You can't change the laws of physics of a universe and still have it be that universe.
In my last post, I gently derided White's ideas about the relation between universes and their laws of physics as follows:
Our universe was not waiting around waiting to be assigned laws of physics and wondering what laws it would get. Our universe is instead properly defined as the universe with these laws of physics, and with these people in it trying to explain fine-tuning.
But Goff makes the point that I am arguably exactly wrong in these assumptions.
Following a suggestion from Manson & Thrush, Goff considers the idea that we ought to identify our universe as the universe growing out of a certain point in the eternally inflating hyperspace. It does seem to make sense to imagine that this incipient bubble universe could have happened to have had other laws of physics, and if so, it also makes sense to consider the possibility that our universe could have had other laws of physics and still have been our universe. Conversely, on this view of the conditions of identity, if another bubble had formed elsewhere in the multiverse and grown into an exact copy of this actual universe, then that would not be our universe and the people in it would not be us. It follows that while a multiverse might help explain why some universe should be fine-tuned, it wouldn't explain why this particular one is.
Having established some prima facie reason to accept this version of the identity conditions (which Goff names "Essential Origins"), Goff proceeds to give reasons to doubt that the Cosmic Essence view makes sense. I don't want to just cut and paste his arguments, which are admirably clear as they are and don't need rephrasing. But very concisely, the main issue is that Cosmic Essence is implausible because it means that any two universes which happen to be identical in internal structure are in fact the same universe on Cosmic Essence, which seems to be absurd to Goff.
However, Goff then charitably attempts to patch Cosmic Essence to see if this problem can be addressed. His suggestion is that we include the position of the universe within hyperspace to be part of its identity conditions. Now, two identical bubble universes which are in different positions within hyperspace are no longer the same universe.
Unfortunately, while this solves one problem, Goff suggests that it raises another. I think Goff over-complicates this issue somewhat, but I think it boils down to the idea that we need to grant the pre-bubble location ("the seed") of the universe an identity in order to satisfy the "location" part of the conditions of identity, but we can't consider that seed to be identical with the universe because it doesn't yet have the universe's laws of physics, and counter-factually could have had other laws of physics. So we're being somewhat extravagant and ad hoc with our assumptions here. It would be more natural, Goff argues, to regard the seed as becoming the universe rather than giving rise to the universe or being replaced by the universe, in the way that an embryo becomes a human. As such we should reject these identity conditions.
Critiquing the assumption of essential identity
First off, I'm not sure why this second problem is such a problem at all. If we want to examine the analogy to human conception a little further, then we can find similar problems there. We can trace human identity back as far as a zygote Z. But that zygote can split into identical twins A and B. By Goff's own argument, twins A and B are not identical to each other, and so they cannot be identical to Z either. It follows that Z cannot simply become A or B but must be replaced by them, which is exactly the situation that Goff thinks is ad hoc and extravagent in the case of the universe seed. Whatever strategy Goff adopts to deal with such issues as they pertain to human identity could presumably be extended to the identity of universes.
For instance, I can imagine that Goff could argue that the fission of an embryo constitutes a discrete event where one entity is destroyed and two new entities are created. But similarly I could argue that the crystallisation of the laws of physics in a bubble universe is such a discrete event, and that the identity of the universe does not exist prior to this. If there is a moment when a human identity can spring into existence then why not the same for universes?
But while I think this problem undermines Goff's argument, this is not how I would answer the challenge myself. Rather I would do away with this notion of essential identity altogether. In this I think I perhaps differ not only from Goff but also from Manson & Thrush. Indeed, my views on this topic are possibly so radical that I expect few to agree with me.
I won't defend my views in any detail here, other than to say that I reject essential identity of persons for much the same reasons that Derek Parfit famously outlined in Reasons and Persons, with discussion of thought experiments such as teleportation. I've written several blog posts already explaining what I think and why. But I'll try to outline what I think very briefly, first on the issue of personal identity and then circling back to the identity of universes.
I don't think there is any fact of the matter on what makes anything the thing it is as opposed to some other thing. I think such ideas are useful human constructs and no more. As such, I reject the apparent implication from Manson & Thrush that we need to know the correct identity conditions to assess White's argument. Instead I say that there are no such identity conditions. In particular, identity conditions should not be relied upon to support arguments about issues on which there presumably is a fact of the matter, such as whether there is a multiverse.
Without essential identity we are left only with which pragmatic concepts of identity are useful to us. In everyday life, our intuitive notions of identity are adequate and are rarely challenged. But challenged they are, in some circumstances. These rare real-life challenges include scenarios such as the bifurcation of embryos into identical twins, dissociative identity disorder and the alteration of personality or memory due to brain injury. Outside of personal identity, there are issues such as the ship of Theseus paradox.
Leaving familiar real-world problems aside, some more out-there philosophical and scientific ideas not only challenge our intuitions but push them to breaking point, as Parfit showed. One particular issue that strikes me is that on the many-worlds interpretation of quantum mechanics it seems that identities of not only embryos but conscious adult humans can bifurcate without limit. Whether or not this interpretation is correct, it seems that we ought to consider how to think of identity in the many worlds scenario, just because it remains a possibility as far as we know. Again, we should not let our intuitions on the subject guide us to accept or reject this interpretation. Our intuitions don't dictate how the universe really is, they are only heuristics for navigating our ancestral environment. If many worlds is coherent even though it conflicts with our intuitions, we should be ready to rethink our intuitions.
The concept of personal identity I find most useful is the idea that I am my mind, where my mind is some combination of my experiences, ways of thinking and memories. Insofar as this mind has developed continuously, I can extend this identity backward and forwards in time. So I say I am the same person as I was yesterday, and indeed in some limited sense I share identity with the original zygote that became me. Even though I would say it didn't have a mind, its development was continuous with the development of my mind. So far, this seems pretty banal, but it has radical consequences if taken literally.
For instance If the MWI is true, my mind has not one but many futures. This means that identity can indeed bifurcate. One person can become two. Each future self will share an identity with the original. But they are not identical to each other. This appears to suggest that identity of persons is no longer quite transitive, as more rigorous mathematical notions of identity are.
All the same, we can translate personal identity to mathematical identity in a couple of ways. We could restrict ourselves to talking only about what is identical to what at a particular time. In this way of talking, the me of yesterday isn't quite identical to the me of today. Apart from having different identity conditions because we exist at different times, we're also different in other ways (e.g. I might have lost some more hair). Another approach might be to consider only the identities of the overall structure traced out by each personal identity as it bifurcates again and again over time. So now, the me on one branch of the universe is just a part of the overall identity, and the me on another branch is another part of the same identity. We're the same person, but not the same part of that person. Whatever way we want to deal with it, it seems clear to me that there's nothing incoherent about the idea that personal identity can bifurcate, even if mathematical identity is supposed to be transitive.
My view also implies that mind uploading and teleportation are not ruled out by identity-related issues (they may be ruled out for other reasons). If I can successfully mind-upload or teleport, the result is me just as much as if I had undergone some more normal transition such as having a night's sleep or travelling. If the procedure has produced a duplicate, then each instance is just as much me as if my identity had bifurcated in the MWI scenario, although the duplicates then proceed with distinct identities from that point on.
Where it gets particularly weird is when we consider the situation where more than one physical person happens to have a mind with identical experiences, memories and ways of thinking over an extended period of time. Consider the possibility that space extends infinitely. If so, then it must be the case that there are infinitely many physical copies of my body and its environment, separated very widely, perhaps in time as well as in space. If so, I sincerely believe myself to be identical to all of them or none in particular. All of them are having the same experience, and there is no fact of the matter as to which of them I am. If half of them are suddenly wiped out in some sort of spontaneous vacuum collapse, for instance, it's of no great concern to me, as my mind will continue to be instantiated elsewhere (this is similar to the idea of quantum immortality).
How should we identify the universe, then? It is just the universe in which I am instantiated. But since a physical person with my mind could be instantiated in any appropriate universe, then "this universe" is just any universe which instantiates my mind. As such I am happy to bite the bullet on the absurd conclusion that Goff rejects, namely:
P2: Any bubble universe (actual or merely possible) with the same physics as U is identical with U.
This seems perfectly plausible to me, although we might want to stipulate that it's not only the laws of physics that matter but also the history or initial conditions. If two universes have the same laws of physics but different initial conditions, then they are presumably not the same universe. So, it does not in fact seem implausible to me to suppose that this universe could be instantiated many times throughout the Landscape Eternal Inflation multiverse, and that there could be more than one physical instance of U which we can deem to be the same universe with the same people within.
But do please note that I am not claiming that this is the objectively correct interpretation of identity. I claim rather that there is no objectively correct interpretation of identity because identity is a human intuitive construct that has no real bearing on reality. This is just the way of thinking about identity that I find most elegant and useful, given various thought experiments that seem to break more traditional or intuitive notions of identity.
If you find these ideas too radical, then perhaps you may have reason to accept Goff's argument. However I think that even if you accept Goff's ideas about identity, it doesn't succeed in undermining the argument for the multiverse from fine-tuning, though it does indeed neutralise the observer selection effect. Instead, accepting all of White's and Goff's assumptions about identity merely places us in the epistemic position of a lottery winner. As discussed on my last post, and again later in this post, this might indeed leave us with reason to suspect that many people had entered the lottery even as it leaves us shocked that we have won it ourselves.
In fairness to White, he anticipated something like this response. White argues that it won't do to I didn't discuss his reasons for rejecting it in my last post, but I'll do so now.
The Total Evidence Requirement
The analogy White draws is as follows:
Suppose I’m wondering why I feel sick today, and someone suggests that perhaps Adam got drunk last night. I object that I have no reason to believe this hypothesis since Adam’s drunkenness would not raise the probability of me feeling sick. But, the reply goes, it does raise the probability that someone in the room feels sick, and we know that this is true, since we know that you feel sick, so the fact that someone in the room feels sick is evidence that Adam got drunk. Clearly something is wrong with this reasoning.
Goff dubs what has gone wrong the Total Evidence Requirement (TER). White says that "in the confirming of hypotheses, we cannot, as a general rule, set aside a specific piece of evidence in favor of a weaker piece." This principle may be correct, but I think the problem might be what constitutes "setting aside" a specific piece of evidence. Certainly we should never ignore any piece of evidence which might have a bearing on an issue. But some evidence is irrelevant and some is not. Where evidence is irrelevant, then it can be ignored.
The problem with the Adam example is that we are discarding evidence which is not irrelevant. If our only reason to think that Adam was drinking is that somebody is feeling sick, and yet we know that the somebody who feels sick is not Adam, then we have no particular reason to think that Adam was drinking. The evidence we are incorrectly setting aside is that the person who feels sick is not Adam. The specific piece of evidence exactly cancels out the generic piece of evidence in this case.
This is not our situation with anthropic reasoning applied to fine-tuning. Here, we infer that there are many universes from the fact that some universe is improbably fine-tuned. I claim that the specific identity of this universe is indeed irrelevant and can be set aside. Goff and White think it is not irrelevant, at least if the universe is our own, because they think that the multiverse hypothesis cannot explain why our specific universe is fine-tuned. This is supposed to undercut the motivation for the multiverse hypothesis, and as such is relevant on their view.
But there is another interpretation. First, as I said in my last blog post, and as Goff does himself, we can split our observations into two propositions. I'll quote Goff's language here as I reiterate the idea.
E1: A universe is fine-tuned.
E2: U is fine-tuned (where ‘U’ rigidly designates the universe we live in).
E1 is explained by the multiverse hypothesis, whereas E2 entails E1 (and so is partially explained by the multiverse hypothesis) but introduces further specific information which is not explained by the multiverse hypothesis. My view is that we should interpret E1 as evidence for the multiverse hypothesis, while remaining surprised by the specifics of E2 (at least if we grant for the sake of argument that we should accept the essential identity of U). I see no reason for E2 to cancel out E1 as happened in the analogy to Adam's drinking. To be analogous to Adam's drinking, we would have to be ignoring some specific reason to reject the link between E1 and the multiverse hypothesis. Such a reason might be an alternative explanation of why our specific universe is fine-tuned, e.g. hard evidence of intelligent design. But the mere fact that E2 remains surprising is not a reason to reject the link between E1 and a multiverse. As such we are not "setting aside a specific piece of evidence" E2 "in favor of a weaker piece" E1. Instead, we simplify by deriving E1 from E2 because the specifics of E2 are irrelevant in our inference to the multiverse. Conversely, the specifics of who was sick was not irrelevant to our inference on whether Adam was drinking.
This is all quite abstract, but the fallacy in White's application of TER is easy to make vivid. Again I'll refer to the lottery example. Suppose that we the chance of any particular ticket winning is very small, and is independent of the number of tickets sold. Suppose also that we have no idea how many tickets were sold. When we learn that Joe Bloggs, a stranger, has won the lottery, should we suppose that many tickets were sold or perhaps as few as one? I hope it is clear that we should suppose that many tickets were sold, because otherwise it is unlikely that anybody would have won.
And yet, the hypothesis that many people bought tickets does not explain why Joe Bloggs specifically won. According to White's reasoning, it is fallacious to ignore the problem of why Joe Bloggs won and to instead answer the question of why anyone won. The inference to the "many tickets" hypothesis would thus be a mistake. This is not quite analogous to E2 as long as the winner is a stranger. So, you can consider the case where you yourself are the winner. The only difference if you have won yourself rather than Joe Bloggs is that you have more reason to be surprised, because you presumably hold ourselves to be more salient than Joe Bloggs. There is no satisfactory explanation for this surprising event. You were just lucky. The inference to the many tickets hypothesis is unaffected.
This is the same situation we are in with regard to explaining why this specific universe is fine-tuned. The inference to the multiverse is justified even if it is surprising that this specific universe is fine-tuned. But it is only surprising that this specific universe is fine-tuned if you accept a strong metaphysical concept of essential identity, which I do not.