Although I had conversations with WLC beforehand, and as you saw I read Sean's blog summary afterwards, I haven't yet watched the actual exchange. I should probably look at it before attempting to answer your question. It may be a little while before I can get around to it. ]]>

I was fortunate enough to stumble upon this very interesting site after reading your comments on Sean Carroll's blog entry regarding his debate with William Lane Craig. I'm not sure if you had a chance to watch their entire exchange, but I would be interested to get your take on how WLC fared if a free moment opens up.

WLC has always struck me as someone who goes to great lengths to ensure that he is on firm scientific ground when presenting philosophical arguments that -- even if indirectly -- rely on current cosmological research. And so I found the criticism that he badly misunderstood/misrepresented the relevant science to be somewhat jarring. (It was especially surprising considering the fact that Alexander Vilenkin recently noted in an email exchange with WLC that his description of the BGV Theorem was very accurate.) Of course as a layman in these matters, I am not sure what to make of those charges and I'd love to hear from an expert who is not deeply committed to a thoroughgoing naturalistic worldview.

Thanks!

]]>However, archaeological evidence shows that prehistoric people (at least those whose remains we can examine) did not live longer than modern day humans; in fact their life expectancy, and the age of the oldest people, are noticably lower. Thus, in general, they did not live longer than us. Which should not be surprising given the much worse medical technology of that time.

If long life were only achieved by a tiny fraction of the population, then of course we would not necessarily know it from archaeology. One could imagine that God supernaturally extended the ages of certain people (given the basic facts of human biology as we know it now, I think this would require a miracle), but we would not be able to scientifically test this unless those people were a part of our sample. This seems especially likely in the case of Abraham, where the whole point of the story is that he and Sarah were much to old to have a child, his body being "dead" as Paul says---and that he had faith anyway that God would do the impossible.

But long lifespans are hardly the worst conflict between modern Science and a literal interpretation of Genesis. The fact is, that any Christian who accepts the modern scientific consensus *must* interpret the early chapters of Genesis nonliterally. Leaving aside the age of the earth and human evolution, the geological evidence simply cannot be squared with a universal Flood. Thus, at least the extreme old ages of the antediluvian patriarchs are squarely inside a portion of the text which we know for other reasons to be mythological (although nonetheless divinely inspired by God, and revealing deep truths in a symbolic way). The symbolic nature of these ages seems reinforced by the fact that some of them seem to have numerological singificance (most strikingly Enoch (365) and Lamech (777)), and that they keep coming tantalyzingly close to 1,000 without ever reaching it, suggesting the inadequacy of even the longest lifespan for attaining complete fulfillment. This lesson from Genesis will be of even greater practical significance if future medical technology allows us to extend the maximum lifespan beyond 120 years.

He lived to be 130 years old, but his years were *few* and *shorter* than that of his ancestors. By all accounts, even incidental ones like this, human longevity shortened dramatically in those years. In addition, if you have a group of people who are living that much longer than their offspring, you can see where the Greek and Roman heroic stories come from. You have a group of people who really do seem to be immune from death giving birth to children who are mortal. Eventually they did die, but this must have been how it seemed to those living at the time.

]]>I confront myself with 1 John 4, first, to brace myself for my own self-examination but my heart leads me to 1 John 2:27. From there I resisted the urge to answer the question myself to myself--after all, I know my answer--what I don't know is if Aron's will re-affirm or take me somewhere else.

I start to read and find myself mesmerized. It's a very comfortable feeling I'm enjoying (similar to when I read Dante or Milton or Homer or Virgil or certain works of Kierkegaard). Now I find myself finished with the analysis. There, I muse, enough said and well done at that! I myself am not so eloquent. But I sure am gratified Aron has taken the time to pose and answer the question with such thoughtfulness and grace and meekness. For myself, I cannot find a single fault with the reasoning and I felt it incumbent to try.

On the other hand I could not understand a single word he was saying in the writing about physics (ha ha).

I also appreciated Andrew's input.

]]>I really don't see how the word "smuggle" is a reasonable description of what I described. We have the wavefunction. We have an obvious metric on the space of possible wavefunctions. I remark that the axiom "probabilities are a continuous function of Psi" is enough to get you (close enough for practical purposes to) the Born rule. Where's the smuggling?

the assumption that "sufficient tiny norm events never happen" seems rather contrary to the premise that "all possible events happen".

But I never suggested making the assumption that sufficiently-tiny-norm events never happen. I suggested making an assumption that implies that as norm -> 0, the probability of the event happening (on any particular occasion) also -> 0. That's an entirely different matter.

about such situations I would be inclined, hesitantly, to say that it is also meaningless what you roll (and therefore that we know we don't live in such a universe)

It seems to me that you should have, at least, a niggling feeling in the back of your mind that you're deriving too strong a conclusion from too little information, when you say "therefore we know we don't live in such a universe".

I suggest the following thought experiment. Consider a one-parameter family of universes, all very much like this one (and, in particular, all having us in them) but with parameterized size. Once the size gets large enough, there are almost certainly "copies" of us with indistinguishable life histories such that (e.g.) any given die roll comes out each possible way; and apparently you know on (for want of a better term) metaphysical grounds that that's absurd and meaningless and "therefore we know we don't live in such a universe". For smaller sizes, this doesn't happen and (so far as I know) you're happy regarding us as living in such a universe. So *what does the transition from possible to impossible look like*? Is a world where there is, let's say, a 10% chance that there's just one other indistinguishable copy of you "meaningless" and impossible? One where there's a 0.01% chance? 10^-100? Even in our world, and even assuming it isn't terribly large (for all we know, last I heard, it might well be), the probability isn't zero. Should we be saying that Pr(roll a 1) = ... = Pr(roll a 6) = *something just a little bigger than 1/6*?

It seems to me that that whole line of thinking must be wrong. The probability that *you* roll a 6 isn't made any larger by the possibility that a copy of you somewhere else might be rolling a 6. Your probabilities have to add up to 1, not to 1 + a fudge factor accounting somehow for the possibility that there are other versions of you elsewhere.

And it also seems to me that if all these finite-but-ever-larger universes are OK and give us the same probabilities (as they must) then their infinite limit is also OK and gives us the same probabilities; and that *cardinality* is a mere red herring. I should in fairness add that although I think I've just given a reason to think it's a red herring, that isn't "my" reason -- it simply seems obvious to me from the outset that "they all have equal cardinality" is no more reason to assign equal probabilities than e.g. the fact that (assuming a traditional continuously-divisible spacetime) the states-of-the-world in which a die comes up 1 and comes up not-1 "have equal cardinality" is reason to assign equal probabilities to *those*.

I'm familar with attempts to smuggle in the Born rule, and they seem rather unconvincing to me. The elegance of MWI is popularly supposed to be that all need is the wavefunction---no need for any additional rules like collapse. But in fact, as you point out, you do need some auxilliary assumptions, in all the rules that you point out. And in particular, the assumption that "sufficient tiny norm events never happen" seems rather contrary to the premise that "all possible events happen".

It seems to me, that once you've specified everything that IS (and saying either 1) "every possibile outcome happens" or 2) the wavefunction is all that exists seem to me to be such specifications), there is no more room for additional arbitrary assumptions. You've already said everything there is to be said about the universe. That would make MWI incoherent.

(Compare a very-large-universe theory that has a universe large enough and random enough that there are almost certainly vast numbers of "versions" of us (with our present surroundings and history) in it. Maybe even an infinite universe, with infinitely many copies of us. Then, e.g., when you roll a die, "with probability 1" there's some version of you somewhere that rolls a 6. But there's no contradiction between that and the fact that (with the usual idealizing assumptions) the probability that you roll a 6 on this occasion is 1/6 rather than 1.)

Actually, about such situations I would be inclined, hesitantly, to say that it is also meaningless what you roll (and therefore that we know we don't live in such a universe). When you roll a die, there are infinitely many versions of you which get a 6, and infinitely many versions where the die explodes and you die, and infinitely many versions of you where green monkeys pop out and start torturing you to death. They are all equally "real", and they occur the same cardinality number of times. Unless you're the sort of person who thinks you die if you enter a star trek teleporter, I think the only correct thing to say is that you would have ALL of these experiences.

Anyway, the question of how to do probability theory in such "mutiverse" type settings is highly controversial, and I'm not aware of any satisfactory general prescription which doesn't lead to horrible paradoxes in certain cases. But, provisionally, because it seems to me the least absurd, I incline to the view that by far the best way to explain the (seeming fact that) some things happen but not others, is that (in reality) some things happen but not others. This requires that the universe not be too large and uniform.

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