最近接连看到引力与宇宙学家Don Page的三篇关于多重宇宙的文章，题目与宗教有关，我也就懒得去看。在更加最近的几天内Don Page给几乎所有研究过Boltzmann大脑的人发了两封信，我就不得不看看他的这些文章到底在说什么。（王一同学和我在夏天写了一篇关于人择原理的 文章，提出了我们关于如何回避Boltzmann大脑的建议，当然，王一同学是这篇文章的主要作者）

Page的神学三部曲：

Our Place in a Vast Universe

Does God So Love the Multiverse?

Scientific and Philosophical Challenges to Theism

必须承认，我是本着一个无神论者的态度来看这些文章的。另一方面，我接触过基督教，所以我对有信仰的人又有一种理解的感觉。

Page既是一位宇宙学家，又是一位基督教徒，他将这三篇文章直接贴到physics archive的做法很不一般。另外，他说，这三篇文章将进入两本文集，其中一本是《Science and Religion: Current Dialogue》，将由北京大学出版。

第一篇文章谈现代宇宙学的主要结果，以及人在其中的位置。Page认为即使我们的宇宙，甚至多重宇宙比地球大得不知多少倍，人还是特殊的。

第二篇文章谈为什么多重宇宙这个概念与上帝创世没有矛盾，其中的一个主要论点是如果多重宇宙作为概念和原理的结果比单个宇宙如我们的宇宙来得简单，那么上帝没有理由不创造多重宇宙。

第三篇文章谈Page想不明白的问题，包括Boltzmann大脑，死后永生的概率，人的自由意志，神的自由意志，神的简单性和可能性，魔鬼，等等。这些问题在这篇文章中居然被像科学问题一样对待，我觉得非常奇怪。也许对于一个基督徒来说一点也不奇怪。

Page在最后一篇文章开头就说现代科学是在犹太教和基督教的有神论的氛围中发展起来的，对于我们东方人来说是一个难以接受却不得不接受的事实。但 Page用贝叶斯统计来讨论人死后的永生我绝对接受不了。他将永生问题和Botlzmann大脑问题同等对待。还有，他居然用多重宇宙来解决魔鬼问题，这在 我看来只能使多重宇宙更加臭名昭著。

什么是魔鬼问题？在有神论者看来，魔鬼的存在很难理解。既然神创造了一切，包括物理定律和初始条件，为什么他要创造魔鬼？一种解释是魔鬼不是神创造 的，是人的自由意志引起的。Page认为这个解释不好。多重宇宙则可以解释，神希望创造出所有可能的宇宙，包括含有魔鬼的宇宙。因为禁止含有魔鬼的宇宙出 现也许不是最简单和最经济的。我不得不说，第三篇文章完全是物理、数学、神学甚至道德的混合体。Page用一句警局结束这篇文章：

科学揭示宇宙间的智慧
圣经揭示宇宙背后的智慧

—————————————————–

关于Botlzmann大脑，见我的博文

关于熵（2）

纽约时报最近有一篇关于这个话题的文章

Big Brain Theory: Have Cosmologists Lost Theirs?

Page给Botlzmann大脑爱好者们的emails

第一封

Dear Colleagues and Friends,

Thanks to many of you for all your help in giving references andother suggestions for the attached three papers expanding lectures that I gave in Shandong University in Jinan, China, last autumn, which are now posted on the physics eprint archives at the following locations:

Our Place in a Vast Universe
Does God So Love the Multiverse?
Scientific and Philosophical Challenges to Theism

If there are any further corrections and/or suggestions that you have, please let me know, as these are going to the publisher soon for the proceedings. A large number of you have been cited in these papers (which may be why you are be receiving this email), and I would like to be sure that I have the citations correct and have properly represented your work.

Best wishes and belated Happy New Year,

Don

第二封

Dear Dennis,

I very much enjoyed reading today your article on Boltzmann brains, “Big Brain Theory: Have Cosmologists Lost Theirs?” in the New York Times at . You did a good job emphasizing that they are a reductio ad absurdum of many versions of current cosmological theories, and that “Nobody in the field believes that this is the way things really work, however.” I think this has been clear to the experts reading my own papers on this, though I have seen that many bloggers have misinterpreted it as saying the universe really is full of Boltzmann brains or that we are really most likely to be Boltzmann brains.

In other words, I am quite certain that I am not a Boltzmann brain, and fairly sure that Boltzmann brains do not enormously dominate over ordinary observers, but I want to emphasize that this should be a consequence of our theories and not something to be tacked on extra. Our
theories themselves should predict this, so as you nicely say, this is a “reality check” on our theories.

I think you quite fairly represented my own views. The only very minor caveat I might point out to the experts (though it would have been too abstruse for the general readership) is that I would not say unequivocally about consciousness that “we have in abundance over the
insects” (what you wrote, not a quote from me). I would just argue that the total measure for insect conscious perceptions should not so much overwhelm the total measure for human conscious perceptions that ours are highly improbable when normalized by the total measure. So I would not worry much about some theory if it turned out that it predicted that the measure for insect consciousness were, say, 10 times that of humans, but I would worry if it predicted that it were, say, 10^10 times that of humans.

Of course, since we don’t know any detailed theories of what gives the measure of onsciousness, a priori it might be surprising if the total measures for insect and human consciousness were within a factor of 10 of each other, or even within a factor of 100, since even the logarithm is highly uncertain. So I would guess that it is more likely that detailed
theories would give either that the measure for insect consciousness would greatly dominate over that for humans (which I would think would make such theories very unlikely) or that it would be the other way around (which I would say is statistically consistent with our observations of being
human). So although for the experts I would not like to be seen as saying that surely the measure for human consciousness is greater than the measure for insect consciousness, I would guess that that will turn out to be the case, since it might take too much fine tuning to make the measure for insects dominate over humans just enough not to make the likelihood for us to observe that we are humans to be too low. But this is just a guess, analogous to my guess that it would require too much fine tuning for there to be not too many extra-terrestials for us not to have found any yet, and nevertheless enough for us to be able to find some in the foreseeable future.

Best wishes,

Don

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