Critical Notice: Frank J. Tipler (1995) The Physics of Immortality: Modern Cosmology, God and the Resurrection of the Dead London: Macmillan pp.xxvi+528

Some people have wondered whether this book is an elaborate joke.[1] Others have suggested that it is merely a cynical attempt to cash in on the current craze for pop physics treatments of 'the big questions'.[2] Yet others have speculated that it may be an ill-conceived attempt to secure funding for expensive, large-scale physics research (cf. pp.335-6).[3] In this notice, I shall ignore these kinds of speculations, and proceed under the assumption that the author is serious and in good faith. It would be very disturbing were this assumption mistaken. Some on the religious right have made, and will make, capital from the mere existence of this book, even if the strict letter of its doctrine provides no comfort to them. We do not need more physicists apparently telling the world that the most recent discoveries in cosmology and particle physics confirm traditional religious teachings. What would it profit Frank Tipler ...?

It is hard to give brief expression to the fantastic speculations which are contained in this book. Perhaps a good place to begin is with the introductory paragraph:

 

This book is a description of the Omega Point Theory, which is a testable physical theory for an omnipresent, omniscient, omnipotent God who will one day in the far future resurrect every single one of us to live forever in an abode which is in all essentials the Judeo-Christian Heaven. .... I shall make no appeal, anywhere, to revelation. I shall appeal instead to the solid results of modern physical science. ... I shall describe the physical mechanism of the universal resurrection. I shall show exactly how physics will permit the resurrection to eternal life of everyone who has lived, is living, and will live. I shall show exactly why this power to resurrect which modern physics allows will actually exist in the far future, and why it will in fact be used. If any reader has lost a loved one, or is afraid of death, modern physics says: 'Be comforted, you and they shall live again.' (p.1)

From this introductory paragraph, the reader will naturally form the impression that Tipler believes the doctrines of the Omega Point Theory. While he mentions that it is a testable physical theory, the rest of the paragraph plainly suggests that he takes it to be a well-confirmed theory (and that the real point he wants to make is that the theory is both physical and testable). Much of the rest of the book confirms this initial impression. However, when we get to Chapter 12 ("The Omega Point Theory and Christianity"), Tipler starts off with the following:

 

To emphasise the scientific nature of the Omega Point Theory, let me state here that I am at present forced to consider myself an atheist, in the literal sense that I am not a theist. ... I do not even believe in the Omega Point. The Omega Point Theory is a viable scientific theory of the future of the physical universe, but the only evidence in its favour at the moment is theoretical beauty, for there is as yet no confirming experimental evidence for it. Thus scientifically one is not compelled to accept it at the time of my writing these words. ... If the Omega Point Theory and all possible variations of it are disconfirmed, then I think atheism .. is the only rational alternative. But of course I also think the Omega Point Theory has a very good chance of being right, otherwise I would never have troubled to write this book. If the Omega Point Theory is confirmed, I shall then consider myself a theist. (p.305)

In the light of this paragraph, it is quite unclear what attitude Tipler actually takes towards his theory. On the one hand, he seems to say that there is nothing but 'theoretical beauty' which tells in its favour;[4] yet, on the other hand, he also say that there is 'a very good chance' that it is true. Perhaps the truth is that Tipler would very much like his theory to be true; until there is evidence or argument which tells against it, there is no reason why one cannot continue to hope that it is.[5] However, his initial talk about 'appeals to the solid results of modern physical science' now seems utterly out of place -- even against the background of modern physical science, the Omega Point Theory is at best a piece of fantastic speculation; and, at least on occasion, Tipler seems to demonstrate that he is perfectly well aware that this is the case.[6]

Perhaps the best way to think about the Omega Point Theory is this. Suppose that one wanted to give a rational reconstruction of traditional theological doctrines in which the letter of those doctrines is preserved, but in which recourse is made only to the concepts of modern physical science. Suppose, further, that one is particularly interested in questions about personal immortality and the resurrection of the dead-questions which have been central to most religions. Then, very likely, the Omega Point Theory (or some 'possible variation' thereof) is the kind of view at which you will arrive. Of course, it is not clear what interest should attach to this kind of inquiry -- in particular, since there is unlikely to be any attempt to preserve the spirit of traditional theological doctrines, it is unlikely that theologians ought to be very interested in the Omega Point Theory. (Some theologians -- e.g. Wolfhart Pannenberg[7] -- have been very enthusiastic about the Omega Point Theory; it seems to me that this can only be due to confusion on their part.) If it were the case that the theory is likely to be true, then everyone would have reason to be interested; but -- as I have already indicated (and as I shall argue further below) -- there is not the slightest reason to think that the theory is true and, worse, there are various grounds for thinking that it is not so much as coherent.

In what follows, I shall provide a slightly more detailed account of the main features of the theory, and I shall indicate some of the more serious difficulties which it faces. I shall also indicate some of the tensions and inconsistencies which appear in the text, particularly when Tipler strays into discussions of strictly philosophical issues. As is the case with many books of this ilk, the result is rather less than the sum of its parts. There are lots of extremely interesting paragraphs on all manner of things -- history, gee-whiz physics, statistics about this and that, and so on. However, given the astonishingly ambitious nature of the work, it is perhaps not surprising that there are also paragraphs in which the quality of scholarship and argumentation is less than excellent. Since my aims in what follows are entirely critical, perhaps I should here point out that, in focussing my attention on the defects of this book, I do not mean to be taken to be indicating that the book is entirely without merit.

1

The structure of the book is as follows: main text: pp.1-339; notes: pp.340-374; bibliography: pp.375-393; appendix for scientists: pp.395-517; index: pp.519-28. The most important thing to note is the large appendix for scientists. In this part of the book, Tipler provides sketches of some of the mathematical and physical foundations for the theory. For the purposes of this notice, I shall ignore the appendix for scientists, and simply consider the material in the main text.

The basic ingredients of the Omega Point Theory are perhaps the following. First, we make an assumption about the large-scale structure of the universe, viz. that it ends in an Omega Point. (More exactly, we suppose that the future c-boundary of the universe is a single point. A consequence of this assumption is that the universe is closed, i.e., that it has a finite spatio-temporal volume). Second, we suppose that it will come to be the case that life exists everywhere in the universe at some time shortly after the point of maximum expansion. Third, we suppose that life is able to 'manage' the collapse of the universe in such a way that life continues to exist everywhere in the universe 'right up to' the Omega Point. Fourth, we suppose that life in the far future will consist of super-intelligent machines which will build enormously powerful computers. Fifth, we suppose that people (and indeed entire universes) can be perfectly 'emulated' on computers, and that all (sufficiently good?) people who have ever lived will be 'emulated' on computers in the far-distant future (and that these 'emulations' will continue to exist 'right up to' the Omega Point). Sixth, we suppose that the universe is globally hyperbolic-possesses a Cauchy surface-and that every timelike and lightlike curve extends to the Omega Point. (Less exactly, we suppose that all of the information from all earlier stages of the universe is 'available for analysis' at the Omega Point.)

Given these assumptions -- whose credibility we shall return to discuss -- we next proceed to the problem of 'placing' the terms of traditional theology in this framework. If we take enough liberties, we can find ways to attribute most of the divine predicates to the Omega Point. Since the Omega Point is actually an ideal point -- not part of the space-time manifold -- it is 'transcendent'. Since total information about all points of spacetime is 'included' in the Omega Point, the world is 'immanent' in it; and, for the same reason, the Omega Point is 'omniscient' and 'omnipresent'. These last two 'conclusions' are further strengthened by the observation that we can think of our cosmological theory as one which is governed by the 'boundary condition' that the universe is such that the biosphere expands to fill the entire universe until the end of time. If we are prepared to 'personalise' this boundary condition, we get a sense in which the Omega Point 'acts' at all earlier times: the entire history of the universe is 'governed' by the final boundary condition. Stretching things even further, we can also use the claim that the final boundary condition 'governs' the evolution of the universe to support the claim that the Omega Point 'loves' living creatures. And so on.[8]

In similar fashion, if we are prepared to make certain assumptions about physical existence and personal identity, then we can claim that computer 'emulation' in the far distant future is 'resurrection'; and that computer 'emulation' right up until the Omega Point is 'eternal life'. Moreover -- with the aid of further assumptions -- we can claim that this kind of resurrection is indeed 'bodily' resurrection, and that it 'coheres nicely' with the claims of all of the major world religions (at least before their doctrines were corrupted by pernicious Greek nonsense about immaterial souls, purely spiritual resurrection, and the like).

Perhaps it is sufficient to put all this down in summary form to make clear how implausible some of it is. While the idea that one might 'place' the terms of traditional theology in the framework of a modern physical theory is not initially plausible, I suppose that one ought to be prepared to judge the results with something like an open mind. However, any attempts to 'place' the terms of one theory within another theory need to be subject to constraints. It is not enough to find single aspects of similarity, vague analogies, and the like: since what is going on is essentially intertheoretic reduction, one needs to show that the terms in the reducing theory are 'good enough deservers' of the 'names' of the old theory. And, in the case in which there is no good enough deserver of the 'names' of the old theory, we should simply conclude that the entities of the old theory do not exist.

So we need to ask: what would it take for an entity to be a good enough deserver of the name 'God'? What would it take for properties to be a good enough deservers of the labels 'omniscience', 'omnipotence', 'omnipresence', 'immanence', 'transcendence', and so on? What kinds of entities can properly be said to 'act', to 'love', to 'govern' and so forth? Once we ask these questions, I think that it is pretty clear that -- as some previous reviewers have noted[9] -- Tipler's attempts to 'place' theological vocabulary in his physical theory are nothing more than word play and abuse of language. For instance, nothing should count as deserving the name 'God' -- by the lights of traditional Judeo-Christian theology -- unless it is a personal creator and sustainer of the universe (where 'personal', 'creator' and 'sustainer' are understood in ordinary and literal ways). Since a single space-time point cannot be a person -- this is a matter of at least metaphysical necessity -- there is no way that the Omega Point can be a good candidate for the name 'God'.[10] Since a single space-time point cannot be an (intelligent) agent -- again this a matter of at least metaphysical necessity -- there is no way that the Omega Point can be properly called a 'creator' or 'sustainer' of the universe. I assume that there is no need to labour this point: a little bit of reflection shows that there is really no justification for the 'placing' of traditional theological terms which Tipler provides.[11] Tipler is an old-fashioned physicalist (and none the worse for that!)[12]; consequently, he is an atheist, and will remain one even if he comes to believe the six assumptions listed above.

Perhaps Tipler might reply that '... [this] strike[s] me as mere quibbles over the meaning of words, and remind[s] me of Appendix IV .. of Hume's An Enquiry Concerning the Principles of Morals: "Nothing is more usual than for philosophers to encroach the province of grammarians; and to engage in disputes of words, while they imagine, that they are handling controversies of the deepest importance and concern."' (p.238).[13] However, this reply involves a misunderstanding: the point of insisting on the meanings of words is precisely to ensure that one does not make silly mistakes in handling issues of the deepest importance and concern. It is only by word play and abuse of language that one could come to think that the properties of a point in a general relativistic spacetime are just the (essential) properties which traditional monotheistic religions attribute to God (and hence that the Omega Point Theory concerns matters of the deepest religious importance). There is no reason at all to think that there is anything in traditional theology which approaches, or indeed remotely resembles, the Omega Point Theory.[14] If theology is to seek comfort from modern physics, it should look elsewhere.[15]

2

Even if Tipler were to concede these points about God, he might still insist that his theory does address some matters of the deepest importance and concern -- for his claims about resurrection of the dead and personal immortality may not be quite so obviously vulnerable to the same kind of objection. Isn't it possible that people might be 'resurrected' in the far distant future by being 'emulated' in super-computers? And if that is possible, won't investigation of the question whether it is likely to happen be an investigation of matters of the deepest importance and concern?

Clearly, these questions can't be fully answered without an excursus into metaphysics. We need to know what are the essential properties of persons, what makes for identity between persons, what are the conditions for the existence of bodies, and so on. Tipler provides discussion of all of these questions, and makes some references to the recent philosophical literature.[16] However -- perhaps unsurprisingly, given the incredible claims which he makes -- I do not think that his arguments will stand much examination.

Amongst the metaphysical claims which Tipler makes -- and in some cases defends by argument -- there are the following:

 

(1) A human being is nothing but a finite-state information processing device. (p.xi)
(2) A human soul is nothing but a program being run on a computer, viz. the human brain. (p.xi)
(3) A person is nothing more than a computer program which can pass the Turing Test. (p.124) (The essential idea of the Turing Test is that what counts for personhood is behaviour: if it behaves in all respects like a person, then it is a person. (p.21))
(4) A living being is just an entity which codes information, with the information coded being preserved by natural selection. (p.124) Life is information preserved by natural selection. (p.126)
(5) If all objects can be truly described by quantum mechanics, then the Many Worlds Interpretation of quantum mechanics is correct. (p.169) Hence, quantum cosmology requires the Many Worlds Interpretation of quantum mechanics. (p.169)
(6) If the Many Worlds Interpretation of quantum mechanics is false, then it is logically impossible for us to have free will. (pp.173, )
(7) A world is indeterministic exactly if there is no proper part of it which contains total information about the whole. (p.187)
(8) An agent acts freely just in case: (i) the agent feels that she is making the decision freely; and (ii) the agent's decision is undetermined at the most basic physical level. (p.202)
(9) An entity is identical to all of its emulations (i.e. precise simulations). (p.207)
(10) To exist physically is to be part of an entity whose emulations are sufficiently complex to contain observers as subsimulations. (p.210) The physical universe is a concept. (p.209)
(11) Existence is a predicate, a relationship between concepts, a property of very complex simulations. (p.210)
(12) To be is to be perceived. (p.211)
(13) If a universe contains observers all the way into the Omega Point, then that universe exists necessarily. (p.211)
(14) A person is identical to any person who has the same 'essential personality'. (p.226)
(15) Continuity over time is not necessary for personal identity. (p.227)
(16) Systems in the same quantum state are identical. (p.230)
(17) It is not possible to derive an imperative sentence from a declarative sentence. (p.330)

Amongst these claims, (1)-(4), (9)-(12) and (14-16) are important for Tipler's assertions about the resurrection of the dead and personal immortality. If I am truly to be resurrected in the future in a computer emulation, then that computer emulation has to be me, and I have to enjoy physical existence in virtue of that computer emulation. But it seems perfectly obvious that nothing can enjoy physical existence in virtue of being emulated in a computer, and that, in particular, I could not enjoy physical existence in virtue of being emulated in a computer. The crucial point is that there should be no conflation of things with representations of those things. A computer emulation of a thing is a (perfect) representation of that thing: but that's all. If the thing is flesh and blood, then the computer emulation represents it as being of flesh and blood -- but this does not mean that the emulation is itself a thing of flesh and blood. (Since we are talking about computers, the emulation might as well be thought of as an electronic encoding of a binary pattern. No flesh and blood there.)

That Tipler does confuse the properties of things with the properties of emulations of those things is clear. Here is the crucial passage:

[L]et us imagine that, when the program is run on some gigantic computer, the temporal evolution of the simulated persons and their city precisely mimics for all time the real temporal evolution of the real people and the real city. ... The key question is this: do the emulated people exist? As far as the simulated people can tell, they do. By assumption, any action which the real people can and do carry out to determine whether they exist -- reflecting on the fact that they think, interacting with the environment -- the emulated people also can do, and in fact do do. There is simply no way for the emulated people to tell that they are 'really' inside the computer. that they are merely simulated and not real. ... How do we know we ourselves are not merely a simualtion inside a gigantic computer? Obviously, we can't know. (p.207)

As far as the emulated people can tell, they do! But, in the relevant sense, there are no emulated people. There are representations -- indeed, perfect representations -- of people in the computer, but there are no people (and, in particular, no 'emulated people') in there.[17] There are representations of the states of consciousness of people in the computer-representations which can be interpretted by real people who have access to the representations in the computer -- but there is nothing which has consciousness in the computer. The 'emulated people' -- the representations in the computer -- don't 'tell' anything, though they may represent people as telling things. And, since we are supposing that these simulations are indeed emulations, they will represent most people as 'telling' that they are not emulations. For, unless one is very sorely confused, one could not suppose that one is an emulation.[18]

I suspect that if Tipler could be convinced on this point, he would give up all of the Berkeleyan speculations involved in (9)-(12).[19] Moreover, were he to do so, he would not need immediately to give up all his claims about a future resurrection. After all, if there will be the technology available to create computers which can emulate people and universes, then surely there will be the technology available to create functional replicas of people. While I can't be resurrected as a computer emulation, I might be resurrected as a robot -- and, since Tipler is supposing that the machines of the far future can exist right up to the Omega Point, why shouldn't it be the case that, once I am resurrected, I exist right up to the Omega Point? Tipler worries that any finite state machine which exists right up to the Omega Point will be subject to Eternal Return; however, there are reasons for thinking that this worry is misplaced. (I shall return to this topic later.)

Could I be resurrected as a robot? Would a functional duplicate of me be me? Should I feel pleased by thought that I might survive in the far distant future as a robot (even if, strictly speaking, there is no way in which I can be identical to that future robot)? These are familiar kinds of questions in the recent literature on personal identity, and they admit of a range of well-known answers.[20] Since there is unlikely to be any causal or informational connection between me and future robots, and since there is no reason why there couldn't be many such robots (one for each minute of my life, perhaps), there are reasons for saying that no future robot will be me, and that what matters for survival will not be present in this case. If all possible 'human' robots were constructed, there would be many that were closely related to me, but it is unclear that I should take any particular comfort from, or interest in, their existence. In particular, given the conditions that will then obtain in the universe, it is hard to see that conditions for the fulfillment of my plans, projects and concerns will be resurrected with me. (Tipler considers the possibility that the global structure of the universe might make all of the information available at the Omega Point. Given an appropriate causal linkage, resurrection would be possible. But, as he admits, there are problems about opacity and loss of coherence which suggest that the information cannot be available. Moreover, there is independent reason to think that the universe does contain event horizons. And, in any case, the information is only available 'at' the Omega Point, so that there is no guarantee that 'your' robot will ever be built.)[21]

The upshot of this discussion is plain (and no doubt was so from the beginning): even if the Omega Point Theory were true, and there were to be computer 'emulations' of all of us in the far distant future, none of us would be resurrected, and none of us would have eternal life. Moreover, even if there were robotic duplicates of all of us in the far distant future, none of us would be resurrected, and none of us would survive. Many of Tipler's metaphysical assumptions are false or confused; and that is enough to undermine this part of his work.[22] (There isn't room here to discuss all of the metaphysical claims which Tipler makes. For example, I would certainly want to dissent from his account of free actions -- (8) -- and his claims about the Many Worlds Interpretation of quantum mechanics -- (5), (6). Moreover, I am sceptical that any precise sense can be attached to his notion of 'essential personality' -- (14).[23] I suspect that there would be very few people who would accept all of (1)-(17).)

3

This brings us back to the six assumptions which I suggested earlier form the core of the Omega Point Theory. Is there any reason to think that these assumptions are correct? I suspect that, in every case, the answer is 'No!' -- and that, in one or two cases, these is reason for saying that these assumptions are not so much as coherent.

1. The universe ends in an Omega Point: This is really just a question for physics. I am quite prepared to believe that it is consistent with the evidence which we now have, and the theories which we now suppose to be at least roughly correct, that the universe will end in an Omega Point. However, I would not be surprised to learn that, in the set of universes consistent with current theory and evidence, the set of universes which end in an Omega Point is of measure zero.[24] In any case, a more salient consideration is that the evidence seems to favour the claim that the universe is not closed, i.e. the universe will simply go on expanding forever. To date, a couple of decades spent searching for the 'missing matter' which would close the universe has not produced any definite results. That is not to say that it won't -- perhaps there is enough 'dark matter' out there waiting to be discovered -- but that is not the direction in which the evidence currently points. Moreover, even if we were to discover that the universe is closed, it is quite unclear that the evidence would support the claim that the universe ends in an Omega Point. Since Tipler himself claims not to believe that the universe will end in an Omega Point, there is clearly considerable room for scepticism.

2. Life comes to exist everywhere in the universe: I am not sure exactly what this claim means. If 'life' were a continuous quantity, then I would know what is required for it to be distributed throughout the universe. But life is not a continuous quantity. Moreover, there is reason for thinking that there are large regions of the universe which could not sustain life. Certainly, life as we know it -- with its reliance on the chemistry of carbon, water, and so on -- can only flourish in quite special conditions which no-one thinks are conditions which will eventually become typical of the universe at large. Of course, it would be unduly chauvanistic to insist that life can only be life as we know it. On the other hand, it does not seem unreasonable to insist that life does require a certain degree of complexity of organisation and structure, and that this requirement does place limits on the locations in which life can appear in the universe. Under conditions of sufficiently low density, there will be no life. So, most of the volume of the universe will be devoid of life (even if packets of life are uniformly distributed throughout). Under conditions of sufficiently high density, there will be no life. In particular, sufficiently close to the Omega Point, when even protons and neutrons have been torn apart, it seems incredible to suppose that there could be life. Perhaps the suggestion is just that every galaxy -- or, less modestly, every star system -- (which now exists?) will eventually be colonised. Even that seems most unlikely (to say the least). We are all too familiar with the vicissitudes of life to be confident that the resources are bound to be available to reach every galaxy (even under the assumptions which Tipler makes about progress in space-craft design, and so on); and, even if the resources are available, there are ever so many other imaginable problems which could get in the way. Co-operative exploration and colonisation has hardly characterised our history: what reason is there to think that our future should be any different?[25]

3. Life exists everywhere in the universe right up to the Omega Point: The main difficulty here is one which I have already mentioned: it is very hard to believe that there is any form of life which could survive in the inhospitable conditions which would obtain in the universe as the Omega Point was approached. True enough, some people have been prepared to fantasise about intelligent beings which dwell in the depths of interstellar space (intelligent clouds of thinly dispersed interstellar dust) or at the cores of stars -- but these suggestions surely are just fantasies. Moreover, in conditions under which quite fundamental particles -- protons, neutrons, and even quarks -- are torn apart, it is hard to see how one could even imagine that life might continue to survive.[26]

4. Life will consist of super-intelligent machines which build powerful computers: This seems to me to be perfectly physically possible. Perhaps Tipler's estimates about when we shall have machines which can pass the Turing Test, and so on, are a little over-optimistic -- but I see no 'in principle' objection to this prediction. Of course, it is a different question whether it is likely to be the case that we are succeeded by -- or become -- super-intelligent machines. For myself, I think it unlikely -- but I concede that reasonable people might well take an opposing view.

5. People can be perfectly emulated on computers; and all of us will be perfectly emulated on computers in the far-distant future: I am happy to grant that people could be perfectly emulated on computers -- i.e. I don't propose to argue that this is so much as physically impossible (it seems plainly logically possible). However, as I have already indicated, I do not see any virtue in conflating representations of persons with persons -- i.e. I do not think that a computer emulation of me could be me, be a resurrected version of me, be my survivor, and so on. Moreover, I see no reason at all to think that we will be perfectly (or even approximately) emulated on computers in the far distant future. It is far from certain that there shall ever be computers powerful enough to emulate people. (Indeed, it is far from certain that human beings shall survive into the twenty-third century.) Even if there are such computers, it is hard to see what reason there could be for those who own the computers to try to produce computer emulations of people who have actually lived. Furthermore, even if those who own the computers do wish to produce computer emulations of people who lived long ago, it is quite unclear that they could succeed. Since there will be insufficient information available via reliable causal channels, the emulations will not be emulations of people who have actually lived. Tipler tries to circumvent this problem by arguing that all possible people will be emulated. However, although that might get around the 'causal connection' requirement, it seems unlikely that it is possible. Tipler claims that, since we are finite state machines, there are only finitely many possible people, and finitely many possible states which they can be in. However, this claim depends upon the assumption that states can be individuated without taking any account of environment and prior history. If the individuation of states is partly sensitive to 'external' considerations, then -- given that the universe is not a finite state machine with only finitely many possible states -- it is not at all obvious that there are not infinitely many possible states that people can be in.[27] It may well be that one would need to emulate every physically possible universe in order to be sure to emulate all people who actually exist -- and it is far from clear that this is even logically possible.[28]

6. The universe is globally hyperbolic, and every timelike and lightlike curve extends to the Omega Point: The condition that the universe is globally hyperbolic is a very strong causal condition which may well not be satisfied in the actual universe. At the very least, there seems to be some reason to think that there are event horizons in the actual universe, e.g. around black holes formed under gravitational collapse. If life were to 'engulf the universe', then presumably there will be living beings which fall into these black holes along timelike curves which are not extendible to the Omega Point. And, in any case, the point remains that it seems very unlikely to be true that every timelike and lightlike curve extends to the Omega Point.

In sum, then: even if we neglect the implausible 'placement' of theological terms in Tipler's theory, and even if we further ignore the metaphysical problems which bedevil his account of 'resurrection', the remaining theory (or bunch of predictions about the future of the universe) is still rather implausible. Tipler makes quite a fuss about the predictions which his theory makes -- e.g. estimates of the mass of the top quark and the Higgs boson, the density parameter of the universe, Hubble's constant, and the amplitude of the density contrast. However, even if all of these predictions turned out to be confirmed, it is quite unclear how much support they lend to his theory. I take it that all of the predictions which I just mentioned are quite consistent with the absence of an Omega Point -- and, indeed, that none of them makes an Omega Point particularly likely. Moreover, these predictions are equally consonant with the failings of the other major planks of Tipler's theory. (One point here is that the prior probability of Tipler's theory is extremely low. And another point is that there are no doubt many other cosmological theories which make the same predictions about the mass of the top quark, and so on, but which have higher prior probabilities.)[29]

4

There are many other features of Tipler's book which should not be allowed to pass without question or comment. I shall mention just a few of them here.

1. Claim: the open universe is not infinite in all directions: At pp.116-9, Tipler provides a very interesting discussion of the work of Freeman Dyson.[30] In particular, he writes:

 

[T]he open universe is not infinite in all directions. Although it is spatially infinite, it is finite in momentum space: there is a universal upper bound to the energy everywhere in this universe. This is important because the state of the universe is given by its phase space position, not merely by its configuration space position. Complexity can increase without limit in a closed universe by using higher and higher energy states to code information. Also, from life's point of view the infinity of configuration space is an illusion. If the universe is roughly the same everywhere, then if life travels sufficiently far in any direction it will run into some other life form's territory. Thus the amount of material available to our descendents is finite, unless they take it away from someone else. This won't happen in a closed universe because the momentum space our descendents will eventually use is currently unoccupied by anybody. And the total energy available diverges to infinity, so there is plenty for everybody. (p.119, Tipler's italics).

I am not sure that I am persuaded by the argument for the conclusion that the infinity of configuration space is an illusion. In particular, I don't see why -- so far as this argument goes -- it couldn't be the case that life arises just once in an infinite universe, and then spreads out from its point of origin 'to infinity'. Provided everyone -- or, at any rate, nearly everyone -- keeps moving outward, I don't see why it has to be the case that the amount of material available to descendents has to be finite, or that there has to be competition for scarce resources. (It seems to help if we assume that the universe is pretty much the same everywhere; and, in particular, if we assume that the density is pretty much the same at all spacetime points.) Perhaps distances of travel would become a problem -- but we don't need to assume constancy of rate of reproduction or length of life before reproduction. Given that we are thinking of our descendents as self-replicating machines, it is hard to see that there is any problem of principle here. Moreover, it seems that things could be so organised that the complexity of the machines increases without limit as 'infinity' is approached. (No doubt, there are contingent features of the actual universe which rule out this scenario -- for one, the density is not roughly constant at all spacetime points. But Tipler's argument doesn't appeal to these kinds of considerations.)

2. Conflation of ontological and epistemological considerations: In his discussion of determinism, Tipler notes that it is important to distinguish between ontological determinism and epistemological determinism (p.189). Similarly, in his discussion of reductionism, Tipler notes that it is important to distinguish between ontological reductionism and epistemological reductionism (pp.294ff.). However, there are various places where Tipler indulges in just the kind of conflation which he elsewhere warns against, appealing to epistemological considerations in an attempt to establish ontological theses. I shall give two examples (there are others):

1. "Any theory of free will that has agent determinism as an ontological ultimate is necessarily based on a Many-Worlds ontology. Agent determinism requires that it is really true that an agent 'could have done otherwise'. However, the only way to be sure that the agent 'could have done otherwise' is for the agent to have done otherwise in actual fact. That is, it is necessary that the agent in fact do two (or more) inconsistent actions. This is of course possible only in a Many-Worlds universe." (p.203) But, of course, it can be true that an agent 'could have done otherwise' even if there is no way for us to be sure (or even mildly confident) that she 'could have done otherwise'. So this argument for the dependence of agent determinism on Many-Worlds ontology is plainly invalid.

2. "If Aquinas knew of the extent of recycling in the biosphere, he would be really worried: were individual atoms distinguishable, a simple calculation shows that the body of every human being on earth would contain atoms that were once part of other human beings. We would all be cannibals. The problem is solved in quantum mechanics, wherein all atoms of the same element are identical. There is no way to distinguish the atoms of the cannibal from those of the victim." (p.236) I don't think that Tipler means to say that there is only one atom of each element (cf. Wheeler's famous remark that there is only one electron). But then, this argument seems to be a complete non sequitur which illegitimately conflates ontological and epistemological considerations. Even if individual atoms are indistinguishable (qualitatively identical), there are still lots of them, and they do have histories, and 'a simple calculation' shows that the body of every human being on earth contains atoms that were once part of other human beings.[31] Of course, we can't tell one atom from another (except perhaps in special circumstances in which they are individuated by relational properties) -- but that doesn't help with the ontological problem. (Furthermore, Aquinas would have insisted that an omniscient being must be able to tell one from another, though not on the basis of their qualitative properties. Since God would know the world-lines of all particles, I doubt that there is too much difficulty here.)

3. Conflation of logical and physical necessity: Tipler makes frequent use of the expressions 'logical impossibility', 'physical impossibility' and 'physical impossibility even in principle'. However, some of his arguments suggest that he doesn't fully understand their significance. Also -- though this is a common problem not confined to Tipler's text -- it is sometimes unclear whether physical possibility just requires compatibility with physical law, or whether it requires compatibility with both physical law and some circumscribed class of physical boundary conditions. I shall give two examples of cases where Tipler seems to conflate logical and physical necessity:

1. "I think it is Searle's basic premise, not the Turing Test, that is fundamentally flawed. A human being could no more hand-simulate a program that could pass the Turing Test than she could jump to the Moon. ... I shall use .. calculation to show that the hand-simulation of a Turing Test-passing program .. is physically impossible, thus refuting Searle's argument". (p.39) Searle's Chinese Room argument [which is the topic of discussion in this quote] is intended as an objection to functionalist analyses of mind. The general idea behind the objection is this: if it is logically possible for a system to be functionally just like us but psychologically quite unlike us, then functionalist analyses of mind are incorrect. But the Chinese Room argument exhibits a logically possible system which is functionally just like us and psychologically quite unlike us. So functionalist analyses of mind are incorrect. It is no objection to this kind of argument to observe that the logically possible system exhibited in the argument is not physically possible -- and there is no correct inference from physical impossibility to logical impossibility. So Tipler's objections to Searle's Chinese Room argument clearly miss their mark. (Perhaps this isn't quite fair to Tipler, for it may be that he misunderstands what the Chinese Room argument is intended to establish. If one could construct an argument for the conclusion that it is physically impossible to make an entity which can pass the Turing Test but which is unable to think, then the Turing Test would be practically vindicated. However, while some candidates -- e.g. the Chinese Room, Blockhead, Peacocke's Martian marionette -- may be physically impossible, there are others -- e.g. Block's China Brain -- which seem to be plainly physically possible.[32] Tipler admits as much, and offers a quite different argument in this case: "Such a modification [i.e. using the entire population of China to hand-simulate the program] destroys Searle's argument, because it is obvious to everyone that the entire human species can 'know' things which no individual human knows. ... So it is perfectly reasonable that the human race .. collectively could speak Chinese, even though no one individual human doing the hand simulation does. An analogue of this occurs in the brain: no individual neuron can think, but the integrated collection of neurons in the brain certainly does ..." (p.41) But, of course, this response completely misses the point. Searle's intuition is that psychological properties (e.g. understanding and consciousness) could not emerge from the kinds of relations in which the persons who belong to the China Brain stand qua elements of the China Brain. That groups of people differently organised can 'know' things which none of them knows individually is utterly irrelevant.)

2. "The Ship of Theseus example tacitly assumes that it is possible, at least in principle, to distinguish continuously between the original ship and the copy to be manufactured. ... But were the Ship of Theseus duplication to be carried out in the far future such that, after duplication, one had two ships in the same quantum state, then it would be impossible, even in principle, to tell which was the original and which the replica. This assertion is a corollary of the No Clone Theorem ..." (p.235) The Ship of Theseus is a logical puzzle about identity: It seems logically possible that there be two things each of which, in the absence of the other, would be identical to a previously existing entity. But they can't both be identical to that previously existing entity; else, by the transitivity of identity, they would be identical to each other (which they are not, since they are two). So there is a question about what to say about this kind of case -- and there is a menu of well-known responses. But it seems pretty clear that one thing which you ought not to say is that it is physically impossible to tell which of the two things is identical to the original -- for, even if that is true, it is obviously irrelevant. Our question is one about the logic of identity, and that question is not one which can be answered by physics.[33] (Again, this criticism may not be enitrely fair to Tipler, since he seems to misunderstand what philosophers mean by 'identity'. In his mouth, 'identity' is 'qualitative identity' (possession of the same intrinsic properties); whereas, in the mouths of the philosophers he is discussing, 'identity' is 'numerical identity' (being one and the same thing). When Flew raises his Replica Objection to resurrection -- no replica however perfect could ever be the same person as its original -- he means that analysis of the notion of identity over time shows that 'resurrected entities' are numerically distinct from their originals. However, Tipler seems to take Flew to mean that it could not be the case that the replica has exactly the same qualitative properties as the original. Since two things can be qualitatively identical -- e.g. the quantum systems which Tipler offers as counterexamples to Flew -- Flew could be refuted by the considerations which Tipler offers if he meant what Tipler takes him to mean. But he doesn't. Tipler allows that there could be quantum replicas of people (though the No Clone Theorem asserts that no machine can make such quantum replicas). So suppose that, at some time -- as a result of a monstrously improbable freak of nature -- a quantum replica of Frank Tipler (as he is at that very time) emerges from a Louisiana bayou. Surely Tipler will concede that this swampman is numerically distinct from him. Moreover, I strongly suspect that he will agree that this swampman has no legitimate legal claims on his family and fortune. And that may be enough to get him to recognise the force of the intuition which drives Flew's argument, even if he still fails to be persuaded by it.)[34]

4. Curious views about 'in principle' considerations: There are various places at which Tipler makes odd -- sounding claims about what is 'possible in principle'. In particular, he makes some odd claims about what mathematics can achieve 'in principle':

One might argue that the universe might be controlled by a 'non-computable' equation, but I don't think there is any real distinction between an equation which requires an infinite number of operations for its solution and no equation at all. One cannot solve such an equation, even in principle: one might as well say, whatever happens, happens. ... I shall define the non-existence of an equation to be equivalent to the inability, by any effective procedure, to write it down in a finite number of symbols, in a mathematically meaningful way. With this definition, the nonexistence of an equation for the universal wave function is established. (pp.190-1) {Mathematically meaningless equations for the universal wave function can be written down -- for example, the wave function satisfies Feynman's famous U=0 equation. This equation is obtained by first gathering all of the equations of physics ... [then rewriting] all these equations by subtracting the expression on the right-hand side of each equation from both sides ... [then] adding up all the squares of these equations. The sum of all the expressions on the left we call U. Clearly, U=0. As Feynman himself said, this 'equation' is absolutely meaningless. It contains no information not in the original equations beyond what the original equations could compute. (p.362n6)}

There are a number of things which one might want to say here. First, it seems very odd to say that U=0 is meaningless. After all, if we unpack it, it yields all of the equations of physics -- and those are most definitely not meaningless. True enough, the equation does not give us anything new, and it is of no practical use (not even as an aid to memory); but those are not grounds for declaring it meaningless. Second, it seems to me that the claim that there are no equations which cannot be effectively written down entails that there are no non-recursive sets, and that there are far fewer real numbers than many of us would care to suppose. After all, it seems that one could use the decimal expansion of pi to construct any number of equations which could only be effectively written down if one could effectively write down the decimal expansion of pi (which, of course, one cannot do). Similarly, it seems that one could use any non-recursive set (of integers, say) to construct any number of equations which could only be effectively written down if one could effectively write down a list of the members of the non-recursive set (which, of course, one cannot do). Third, I don't see why we are obliged to say that 'non-computable' equations cannot be solved even in principle. I suppose it would be grasping at straws to suggest that Church's Thesis might be false; and I do not know enough about the notion of 'continuous' and 'quantum' computers to know what they might be able to do. But there is a quite different way in which 'non-computable' equations are soluble in principle -- namely, by use of an infinity machine. While machines which can carry out supertasks are philosophers' fantasies -- they are almost certainly not physically possible -- they are not logically impossible (and surely that is all that is needed for the in principle solubility of 'non-computable' equations).[35] Again, one might be inclined to think that there is a conflation of ontological and epistemological issues here -- mathematical Platonists may very well think that there are equations which are insoluble in principle.

5. Claim: proper time is not the appropriate time-scale for life: In a number of places, Tipler makes interesting claims about the nature of time, and the different kinds of times (and time-scales) for which we might find use in our theories of the universe. In particular, Tipler distinguishes between proper time (the familiar time of physics which is measured by atomic clocks), subjective time ('the length of time it takes an intelligent being to process one bit of information -- to think one thought' (p.134)) and eternity (the 'union' of proper time and subjective time (p.155)). Tipler suggests that subjective time is the 'appropriate' timescale for life (p.266), and that 'any timescale is as good as any other' when it comes to proper time (p.102). In particular, he claims that Milne time and York time -- both of which go from minus infinity to plus infinity -- are perfectly good timescales for closed universes, and that we can appeal to these timescales in order to argue for the conclusion that it is meaningless to ask what came before the initial singularity or after the final singularity: "In York time, the universe has always existed and always will. Thus to ask what happened before the initial singularity is the same as asking what happened before an eternal universe came into existence. A meaningless question, surely." (p.102) I do not think that this last argument can be any good. After all, the symmetry of the situation suggests that one could equally well argue that there are 'perfectly good' timescales for open universes which run over a closed, finite interval -- and that this is a reason for saying that it makes perfect sense to ask what happened before the initial singularity or after the final singularity in such universes. More importantly, the crucial question really has nothing to do with the choice of timescales, but rather concerns the extendibility conditions which are placed on the space-time. As John Earman writes: "[I]t remains open that there is some mathematically meaningful extension -- involving lower continuity/differentiabliity conditions than those required for a physically meaningful extension -- and that God or some other metaphysical cause operates in this mathematical time.[36] "Tipler's remarks about subjective time are also open to question: there is at least room for suspicion that there is some kind of level-confusion involved in the claim that single thoughts correspond to the processing of single bits of information; there is also room for doubt about the idea that it is possible to provide a discrete individuation of thoughts; and there may be grounds for scepticism about the idea that there could be a discrete subjective time based on the linear processing of bits of information in the brain.[37]

5

Apart from the dubious inferences mentioned in the previous section, Tipler also provides some arguments which students with even a little experience in philosophy would probably repudiate. In the appendix for scientists, Tipler claims that one would need Ph.D.s in at least three different fields -- global relativity theory, theoretical particle physics, and computer complexity theory -- in order to fully understand the theory.[38] I suspect that a slightly lower level of expertise in philosophy suffices for understanding of some of the deficiencies of his book. Again, I merely provide a representative sample:

At p.3: "Either theology is pure nonsense .. or else theology must ultimately become a branch of physics. The reason is simple. The universe is defined to be the totality of all that exists, the totality of reality. Thus, by definition, if God exists, He/She is either the universe or a part of it. The goal of physics is understanding the ultimate nature of reality. If God is real, physicists will eventually find Him/Her." The word 'universe' is tricky.[39] It can mean 'the totality of all that exists'; but it can also mean something like 'the sum [=mereological aggregate] of all the things which are spatio-temporally connected to us'. The latter -- also sometimes referred to as 'the physical universe' -- contains all of the things which are the proper subject matter of physics; but the former may be more extensive (since it may be that the objects of mathematics, set-theory, logic, and various other disciplines are not denizens of the physical universe). Moreover, even if everything is physically constituted and governed totally by physical laws, it may still be that there are [supervenient] entities which are properly studied by disciplines which are not branches of physics. After all, the claim about constitution and governance is an ontological claim; but the claim about proper objects of study is epistemological -- it could be that our epistemological limitations ensure that the special sciences remain forever autonomous in practice even though there is an in principle reduction of all of them to physics.

At p.80: "The Eternal Return implies racism. ... This is a consequence of the Eternal Return: if there is no progress at all, then in particular there can be no progress in evolution. Every species should look after its own interest rather than hoping for the betterment of all. There is no betterment of all." I have already noted that Tipler later asserts that it is not possible to derive an 'ought' from an 'is', and that claims about values are logically independent of claims about facts. So, by his own lights, what he claims about the implications of the doctrine of Eternal Return -- the purely factual claim that every state of the Universe repeats itself over and over -- cannot be correct. Moreover, it seems clear that this particular attempt to derive 'ought' from 'is' is not successful: just because there is 'no progress in evolution', it plainly does not follow that every species should look after its own interest. Why shouldn't one think that, if everything is repeated over and over, then one has an even greater responsibility to do the morally correct thing? (Perhaps it's also worth noting that there can be lots of local progress by evolution in a world of Eternal Return. Why shouldn't one think that one has a moral obligation to make things better around here, even if there will be subsequent times at which things are worse?)

At p.125: "This definition of life [that life is information preserved by natural selection] has some counterintuitive consequences. ... [It means] automobiles are alive. They self-reproduce in automobile factories using human mechanics. Granted, their reproduction is not autonomous; they need a factory external to themselves. But so do male humans: to make a male baby, an external biochemical factory called a 'womb' is needed. ... The form of automobiles in their environment is preserved by natural selection: there is a fierce struggle for existence between various 'races' of automobiles. Japanese and European automobiles are competing with native American automobiles ..." Surely Tipler's definition of 'life' does not have the counter-intuitive consequence that automobiles are alive. Even if these is some loose analogy between automobiles and biological species, it is false to claim that automobiles evolve by natural selection. It simply isn't the case that new models of cars arise because of random mutations in genetic material -- and yet this is part of what is required for any process to count as evolution by natural selection.[40] Perhaps Tipler might insist that we ought to understand 'natural selection' more broadly here: "The key feature of the 'living' patterns is that their persistence is due to a feedback with their environment: the information coded in the pattern continually varies, but the variation is constrained to a narrow range by this feedback" (p.125). But this 'broader' definition is plainly unsatisfactory: no reasonable definition of 'living thing' can allow that any manufactured entity which involves a feedback loop -- e.g. a thermostat -- is a living thing. (Part of the problem here is that the persistence of these kinds of things involves 'unnatural selection' -- namely, selection by living things on the basis of their interests, etc. Genuinely living things must have more independence.)

At p.159-60: "If we know the values of the field on any proper subset of the spherical surface, then the field has almost complete freedom to take on virtually any value at any point in the interior of the sphere. ... However, if we know the field on the whole of the surface of the sphere, then it is a theorem that the field is uniquely determined in the entire interior of the sphere. ... Similarly, if God is pictured as separate from spacetime, and if total information concerning the structure of spacetime is coded both in God and in spacetime, then spacetime has no freedom; it is completely determined by God's omniscience." Clearly, compatibilists will think that there is no problem here: just because spacetime 'has no freedom' in the sense of Tipler's discussion, it does not follow that people who are denizens of spacetime 'have no freedom' in any sense worth caring about.[41] However, it is also fairly plain that libertarians need not be too concerned by Tipler's argument. For all that this argument shows, it could be the case that the information coded in God depends upon the information coded in spacetime -- i.e. it could be that, even though God is omniscient, spacetime has plenty of freedom in Tipler's sense. If Tipler replies that this kind of dependence is ruled out by the stipulation that God is 'separate from' spacetime, it is still not clear that all it lost: perhaps one could think that there is 'co-variation without determination' between the information coded in spacetime and the information coded in God. At the very least, given the 'separateness' requirement and the co-variation, it is quite unclear why it is spacetime which is said to be lacking in freedom. Given the symmetry of the situation, why not attribute freedom to the combined system (spacetime+God), and leave it at that?

At p.212: "Consider a segment of a single history, and in this history, focus attention on an instant of time. This instant of time comprises the entire physical universe as we now see it, at this instant. .. Let us now imagine this set of initial data evolving into the future, under the control of the laws of physics. .. Let us now suppose that the laws of physics and the initial conditions are such that at some future time Te, all life in this history necessarily becomes extinct. That is, any further evolution into the future using the given laws of physcis will be a lifeless history, for all future time. The entire history exists mathematically, in the class of all logically consistent simulations, but it collapses into nonexistence physically the instant life dies out. .. If these is no life in the universe to observe its existence, then by the definition of physical existence this simulation, this universal history, simply does not exist physically. However, if there is a modification of the laws of physics in that history for which life will continue to exist after Te, then the history with the laws of physics modified at time Te exists physically. That is, the laws of physics, as they hold over all time, and the universal boundary conditions necessarily permit life to continue to exist forever. This proves the Eternal Life Postulate." (Tipler's emphasis) There is a lot one might say about this argument, particularly since it is so unclear what the argument is supposed to be. I take it that the conclusion of the argument is that the universe must be capable of sustaining life indefinitely, and that the main premise which is supposed to support this conclusion is that physical existence requires living observers. However, there must be something wrong with this argument, since we know -- and Tipler grants -- that for most of its past history, the universe has lacked life. (Certainly, the Alpha Point of the Big Bang was not inhabited by supercomputers running simulations of all of the creatures which would subsequently exist.) But then it cannot be that the physical existence of a universe requires life everywhere -- and so there is no reason at all to suppose that the current physical existence of the universe is grounds for thinking that the universe must be such as to permit life to continue to exist forever. (There are interesting questions for Tipler's theory which are raised by the apparently time-symmetric nature of physical laws. Why an Omega Point and not an Alpha Point? Why is it so good to have life continuing indefinitely into the future, and yet unimportant that life has not always existed in the past?)

At p.228: "Flew is wrong about our legal system. It does in fact equate identical computer programs. If I duplicated a word processing program and used it without paying a royalty to the programmer, I would be taken to court. A claim that 'the program I used is not the original, it is merely a replica' would not be accepted as a defence. ... Identical twins are not identical persons .. but two beings who are identical both in their genes and in their mind programs are the same person, and it is appropriate to regard them as equally legally responsible." Here, Tipler seems to be involved in some kind of confusion about the distinction between type-identity and token-identity. For many kinds of things -- such as pieces of music, letters on a page, and computer programs -- it is appropriate to think of the particulars which belong to the kind as tokens of a given type. In the case of the computer program, if I duplicate your programme, then I make for myself a token of your programme. However, what you have rights to is the type of programme -- and it is this which guarantees you royalties for all of the tokens which are produced by copying from your original token. (My programme and yours are not token-identical, but they are type-identical.) Suppose, then, that we agree that we can apply the type/token distinction to people: there can be distinct people-tokens of the same people-type. Even so, it is the individual tokens which are involved in particular actions, and which are the subjects of moral responsibility. (Suppose that I am on the moon at the same time as another token of my type commits a murder on the earth. Why should I be held responsible for what this other token of my type has done?) Of course, we might well be sceptical about the use of the type/token distinction in connection with people: for, even though there is no reason why there should not be distinct people-tokens of the same person-type at a given instant of time, those distinct people-tokens will surely belong to different person-types (on any reasonable scheme of individuating person-types) as time goes by. (This is one consideration amongst several which threatens the coherence of my little story about my visit to the moon. The important point is that these considerations would tell equally against Tipler's claims about legal responsibility.)

At p.298: "As Weinberg responded, a previous discovery in the subatomic world -- nuclear fission -- has already had a profound impact on the middle world. This discovery has forced us to deepen our understanding of the important middle world phenomenon of 'war': when is a war a 'just war'? (A nuclear war is not just a war.)" Perhaps there is a typographical error in that parenthetical appendage. Is Tipler aware that a 'just war' is a war which is justified? Is he perhaps making a rather poor attempt at a joke?

At p.319: "Scientists have been very suspicious of the Aristotelian notion of substance ever since the time of Galileo, when the Aristotelian philosophers argued that the changes and imperfections observed in the heavens by Galileo and other astronomers had to be merely optical illusions, because the celestial substance .. was by nature unchangeable and perfect." Tipler is here discussing the use of the words 'substance' and 'accident' in Thomistic metaphysics, so it is a general suspicion about these categories which is at issue. The fact that the Aristotelian philosophers were deeply wedded to some mistaken ideas about what falls under the category of substance provides no grounds at all for suspicion about the category. (One might as well think that there is reason to be suspicious about the category of objects because there are no ghosts.) I doubt very much that scientists -- whether at the time of Galileo or later -- had anything like this feeble ground for suspicion of the general ontological category of substance.

At p.329: "Aquinas in fact was one of the leading scholars of the Aristotelian physics of his day, and it was primarily Aquinas who was responsible for the general acceptance of Aristotelian physics throughout Europe. We could with justice call Aquinas a great physicist as well as a great theologian, for, although Aristotelian physics was wrong, it was an essential precursor of modern physics." I do not think that we would say that modern authors of best-selling physics text books must qualify as great physicists. Instead, we would insist that, in order to be a great physicist, one has to make an important original contribution which enlarges the store of physical knowledge. Judged by this kind of criterion, I know of no reason to think that Aquinas was a physicist, let alone a great physicist. Also, I'm not sure that Aristotelian physics is an essential precursor to modern physics. It seems easy enough to imagine a Greek Newton ...

6

In closing, it is perhaps worth noting some global features of the book which some readers may find a little irritating.

Tipler is quite fond of what look very much like arguments by appeal to authority. ("Nobel laureate Paul Dirac was the first physicist to argue for the postulate of eternal life." (p.11) At p.xii, where he is quoted saying something with which Tipler agrees, Steven Weinberg is a "Nobel-prize-winning physicist"; at p.69-70, where he is quoted saying something with which Tipler disagrees, Steven Weinberg is merely "an American physicist". On the other hand, at p.101, Eugene Wigner is a "Nobel-prize-winning physicist" even though he is objecting to something which Tipler says -- though here the uncharitable might think that the emphasis is on the quality of audience which Tipler's talks attract.) Moreover, there are many places where he claims that someone has established, or argued for, a result, and then no indication of the line of argument or evidence is given.[42] Perhaps this is inevitable in a popular book, but the upshot is that many important issues do not get discussed.[43]

Perhaps because this is a popular work, there are several places where Tipler skates very quickly over large amounts of fairly treacherous terrain. One case in point is the section "The Eternal Return in Philosophy, Religion and Politics". This section begins with a couple of pages on this history of the notion of Eternal Return (pre-history, Babylon, ancient India, the Stoics, Aristotle, Plato, Augustine, medieval China). Next, there are a couple of pages on the conception of Eternal Return in Nietzsche and Heidegger. Then there are about eight pages discussing the connections between Nietzsche, Heidegger and Nazism. ( "Heidegger has correctly identified his opponent, the opponent of the Eternal Return, the opponent of Nazism and all that these stand for: the book you hold in your hands is a work on cybernetics -- the old word for 'computer science'."(p.86))[44] Next, there are a couple of pages on cybernetics, and the fear of robot intelligence in the West. ("The Japanese welcome robots into their factories. They do not fear the arrival of robots with human-level intelligence ... In the West, machines are often the cause (or the excuse) for throwing people out of work, whereas in Japan a worker whose job is automated is simply assigned other (more productive) work. So the Japanese have never had cause to regard robots as a threat." (p.88))[45] Finally, there is a discussion of cultural relativism, and the 'decisive refutation' of the pernicious Kuhnian theory of scientific revolutions. ("Steven Weinberg and Sheldon Glashow ... have both sharply criticised Kuhn's theory, pointing out that the Standard Model revolution did not occur the way Kuhn would lead one to expect. ... John Polkinghorne .. has said exactly the same thing. All three physicists agree that the physics community accepted the Standard Model on purely objective, rational grounds." (p.89)) Some of this is almost 'stream of consciousness' writing; it would require a lot of very likely unrewarded effort to analyse it properly.[46]

Finally, it is I think worth noting that Tipler nowhere explicitly addresses the question whether it is plausible to suppose that 'anthropic' boundary conditions -- such as his Omega Point Boundary Condition -- can be crucial, central planks in physical theories. What unity there is to the theory which Tipler develops in the book is due to this condition -- we begin with the assumption that life lasts forever, and develop our theory accordingly. But it seems to be the case that we currently have lots of good physical reasons for supposing that life does not last forever (cf. the discussion in section 3 of this notice). So there seem to be reasons for thinking that the physical credentials of the theory are more than a little suspect. (The earlier discussion also suggests that the 'unifying' power of this principle is less than Tipler supposes -- the claims about 'God' and 'resurrection' could well be defeated even if this principle proved to be correct.)

At p.338, Tipler writes: "I began this book with an assertion on the pointlessness of the universe by Steven Weinberg." Alas, the quote in question occurs on p.69. In a book so concerned with beginnings and endings, this carelessness is rather ironic. Unfortunately, I suspect that this particular claim of Tipler's is almost certainly closer to the truth than most of the important theses which he undertakes to defend.

Notes

[1] In the first paragraph of the Preface, Tipler writes: "One naturally wonders if I am serious" (ix). He immediately goes on to add: "I am quite serious".

[2] See, for example, G. Ellis (1994) "Piety in the Sky" Nature 371,8, p.115. Ellis' review is extremely savage: it calls Tipler's book 'a masterpiece of pseudoscience ... the product of a fertile and creative imagination unhampered by the normal constraints of scientific and philosophical discipline' and asserts that 'what one would have assumed was just an undergraduate joke is here presented as if it were a serious theory'. I wonder whether Ellis has a religious barrow to push. He writes: ".. the book will make things much more difficult than before for those engaged in the debate about the relationship between science and theology, a debate that is gaining momentum." I would have thought that Tipler's book-and, indeed, pretty much any book-would be easy to ignore for those who wish to do so.

[3] This is my own speculation. It is at least as plausible as the first two which I have mentioned, but I have no reason to think that it is correct.

[4] Tipler's conception of 'theoretical beauty' here seems to be rather idiosyncratic: certainly, it is not clear to me that the Omega Point Theory is beautiful in the sense in which Special Relativity is beautiful. Indeed, the main 'beauty' of the Omega Point Theory seems to be that it promises to fulfill common human desires. Why else is a theory in which life lasts forever more 'beautiful' than one in which life dies out?

[5] At p.16, Tipler writes: "Let me emphasise again that the Omega Point Theory, including the resurrection theory, is pure physics. There is nothing supernatural in the theory, and hence there is no appeal, anywhere, to faith." But there is not much difference between hope and faith, at least in the present context.

[6] It also seems clear that there is considerable justice in the allegations of 'false advertising' which Ellis, op. cit., makes against Tipler. Given that Tipler does not believe the theory which he is expounding, he ought not to write in ways which suggest that he does believe it. It is not uncommon for readers to only get part way through a book ....

[7] See, for example, his "Theological Appropriation of Scientific Understandings: Response to Hefner, Wicken, Eaves and Tipler" Zygon 24, 1989, pp.255-71

[8] Lest it be thought that I am being unfair to Tipler, let me give some of this in his own words: "[I]n order for the information processing operations to be carried out arbitrarily near the Omega Point, life must have extended its operations so as to engulf the entire physical cosmos. We can say, quite obviously, that life near the Omega Point is omnipresent. As the Omega Point is approached, survival dictates that life collectively gain control of all matter and energy sources available near the Final State, with this control becoming total at the Omega Point. We can say that life becomes omnipotent at the instant the Omega Point is reached. Since by hypothesis the information stored becomes infinite at the Omega Point, it is reasonable to say that the Omega Point is omniscient; it knows what it is possible to know about the physical universe (and hence about Itself)." (pp.153-4) Since the Omega Point is an ideal point-a mathematical abstraction, no part of the space-time manifold-we should not want to follow Tipler in claiming that properties which tend to limits as the Omega Point is 'approached' from within the manifold are instantiated at the Omega Point. So, even if we thought that 'information storage' does approach infinity as the Omega Point is approached-and even if we thought that 'omniscience' is a good label for 'infinite information storage'-we should still not want to say that the Omega Point is infinite. However, it is also plain that we should not think that 'omniscience' is just 'infinite information storage' in Tipler's sense. (This is so even if we allow that all physically possible worlds 'collapse into' the Omega Point, as Tipler's version of the Many Worlds/Histories interpretation of quantum mechanics allows.) An omniscient being should know all about about physically impossible but logically possible worlds-yet there is no reason at all to suppose that this information will be 'stored' at the Omega Point.

[9] Ellis, op. cit.; also J. Polkinghorne (1995) "I am the Alpha and the Omega Point" New Scientist, 4 Feb 1995, pp.40-1: "Throughout there are references to theologians. These often seem to trade upon verbal parallels which require much more careful evaluation." (Polkinghorne goes on to say that there 'is an interesting degree of parallelism', suggesting that his enthusiasm for my line of criticism of Tipler would not be unequivocal.)

[10] Perhaps it isn't quite right to call the Omega Point 'a single space-time point'. As I have already noted, the c-boundary is not attached to the space-time manifold. Tipler writes: "[M]athematically speaking, the c-boundary is a completion of space-time: it is not actually in space-time but rather just 'outside' it. [Moreover], a c-boundary consisting of a single point is equivalent to the entire collection of space-time points (regarded as a unity) and a certain infinite collection of subsets of space-time points (all past light cones)" (p.154). The real significance of this observation is that the Omega Point is an ideal point which is used to characterise the boundary of space-time, but which is not itself part of the space-time manifold. This observation does not serve to justify Tipler's further remarks about the 'immanence' and 'transcendence' of the Omega Point.

[11] At p.xiv, Tipler writes: "... the old theological words retain a rough coherence in the popular language, and I propose to reintroduce them as technical terms which, as the reader will see ... have roughly their popular meaning." I think that it is obvious that Tipler ought to have taken the advice of his fellow physicists who advised him to avoid using these words-though not for the reason which they give. The problem is not that "these words ['God', 'Heaven', 'free will'] have been debased by philosophers .. into synonyms for 'nonsense'"; rather, the point is that these words have perfectly good uses in (popular) language which are dramatically at variance with the uses to which Tipler wishes to put them (and nothing but confusion can result, especially given his insistence that there is 'rough' equivalence of meaning). Of course, there could hardly be a competent speaker of English who thinks that 'God', 'Heaven', 'free will' and 'nonsense' are all synonyms (though no doubt there are some who think that no sense can be attached to the first three of these words).

[12] A qualification is needed here: most of the time, Tipler reads like a good old-fashioned physicalist. However, in Ch. VIII ("The Omega Point and the Physical Universe Exist Necessarily") he appears to defend a kind of Berkeleyan idealism. I shall have more to say about this seeming inconsistency in his views later.

[13] Tipler's other avenue of reply is to say something like this: "I have shown at length in this book that the Omega Point Theory is consistent, broadly speaking, with the core beliefs of all the great world religions" (p.337) (my italics). Of course, since anything is like anything else in ever so many ways, sufficiently broad speech can make the Omega Point Theory consistent with just about anything.

[14] There are many places in the book where Tipler says that one theory is 'the same as' or is 'amazingly simialr to' another theory from which it differs greatly. For example: "There is actually an astonishing similarity between the mind-as-computer-program idea and the medieval Christian idea of the 'soul'." (p.127) "Israel ben Eliezer ... emphasises the earthly nature of the afterlife. ... This is essentially the same as the afterlife in the Omega Point Theory." (p.290) "The doctrine that God is continually destroying and recreating the universe from moment to moment ... is quite similar to the view of the human body in modern quantum field theory, which pictures it as being annihilated and re-formed many times per second." (p.300) There are many similar passages in Tipler's book.

[15] My talk-in this section-about 'placing' the terms of one theory in another theory alludes to Frank Jackson terminology in his discussion of what he calls 'the placement problem' in metaphysics. (See his Locke lectures, forthcoming.) The general ideas about intertheoretic reduction are due to David Lewis.

[16] There is quite a bit of philosophical material in Tipler's book. Perhaps the most important sections-from this perspective-are the following:

Ch.2 #2: Can a machine be intelligent (esp.pp.38-43 on Searle's Chinese Room)
Ch.3 #2: The eternal return in philosophy, religion and politics
Ch.4 Physics Near The Final State: The Classical Omega Point Theory

        #1: Computer definitions of 'life', 'person', 'soul'
        #2: What does it mean for life to exist forever?

Ch.7 How Free Will Can Arise From Quantum Cosmological Mechanisms
        #1: The distinction between determinism and indeterminism
        #2: Avoiding the conflict between divine omniscience and human free will

Ch.8 The Omega Point And The Physical Universe Necessarily Exist
        #2: Simulations and emulations
        #3: The algorithm for deciding which concepts exist physically

Ch.9 The Physics Of Resurrection Of The Dead To Eternal Life
        #6: The pattern (form) theory versus the continuity theory of identity
        #7: The ship of Theseus
        #8: Continuity theory: a later emulation is identical to the original person

Ch.11 #2.3 The definition of 'reductionism'

[17] Perhaps this talk about there being 'representations in the computer' also needs to be handled with care. I take it that this talk could be shown to be perfectly respectable, but it is something which probably requires some argument.

[18] Tipler's 'key question' is reminiscent of familiar sceptical worries: am I deceived by a deceitful demon? am I a brain in a vat? have I been plugged into an experience machine? is it all just a dream? However, in all of these scenarios, the key question is not whether I am real-that question is never in doubt-but rather whether my experience is veridical. To suppose that I might just be a representation is to enter a quite different -- and utterly incoherent -- realm of speculation.

[19] Of course, there are plenty of independent arguments which could be levelled against (9)-(12). I would certainly wish to object to all of them (except perhaps to the claim that existence is a predicate, at least when this is properly understood). However, it would take us too far afield to properly explores these issues here.

[20] Two classics of this literature are: J. Perry (ed.) (1975) Personal Identity Berkeley, CA: University of California Press and D. Parfit (1984) Reasons and Persons Oxford: Clarendon.

[21] For the purposes of this discussion, I ignore the issues raised by the debate between internalism and externalism about content. See the next section, thesis 5, for further discussion.

[22] Tipler is well-known as the co-author, with John Barrow, of The Anthropic Cosmological Principle (Oxford: OUP, 1986). Anthropic principles do not make very many appearances in the present work. However, at p.152, Tipler provides what looks like an anthropic solution to 'the Isotropy Problem': the reason why the cosmic background radiation is isotropic is that 'otherwise the universe in the far future would be inhospitable to life'. Perhaps it isn't quite right to claim that this solution is anthropic: for according to Tipler's theory, the evolution of the universe is governed by the "Omega Point Boundary Condition for the universal wave function: the wave function of the universe is that wave function for which all phase paths terminate in a future Omega Point, with life continuing into the future forever along every phase path in which it evolves all the way into the Omega Point" (p.181). However, there is surely some justice in the claim that this an anthropic boundary condition: the universe is said to have this boundary condition precisely because it must have this boundary condition if life is to continue forever. The usual disputes about anthropic principles should now arise.

[23] Tipler claims, for example, that someone who has Down's Syndrome might be resurrected 'by' the Omega Point in an 'improved' form in which they no longer have Down's Syndrome, and yet in which they have the same 'essential personality'. (See p.243. I have more to say about this claim later.)

[24] Note that I would not conclude from the claim, that the set of universes which end in an Omega Point is of measure zero, either that our universe does not end in an Omega Point, or that it is certain that our universe does not end in an Omega Point. Contrast Tipler: "It is intuitively clear that if the number of trials is infinite, the probability that we eventually return to 1 is 1; which is to say, it is essentially certain. ... Hence we have eternal recurrence." (p.96) That an event has probability measure zero does not mean that it does not happen, nor that it is certain that it does not happen. So Tipler's inference here is invalid, even though he could reasonably conclude that it is quite likely that we eventually return to 1.

[25] At p.154, Tipler writes: "When life has completely engulfed the entire universe, it will incorporate more and more material into itself, and the distinction between living and nonliving matter will lose its meaning". This suggests that he thinks that life could exist everywhere even if there were lots of non-living material; but it doesn't clear up what he means by 'life exists everywhere'. (The last claim in the quote requires correction. A distinction does not cease to be meaningful just because one of its terms happens, contingently, to cease to be instantiated.)

[26] This point is noted by Ellis, op. cit.: "This ignores the fact that the indefinitely rising temperature in such a Universe would dissociate not only molecules and atoms but even nucleii into their fundamental constituents. ... Both the reliable storage of complex biological information and its systematic and highly controlled hierarchical processing would be completely impossible in these circumstances."

[27] Tipler considers something like this problem when he considers the suggestion that one could only 'emulate' a person if one emulated their entire universe, owing to the 'quantum entanglement' of the person with the universe. He claims that emulation need not require perfect simulation at the quantum level, but it is far from clear that this is correct. And, in any case, the problem raised by 'externalism' is quite independent of the problems allegedly raised by 'quantum entanglement'.

[28] The logical problem is that, if the universe contains all these emulations, then the emulations must contain emulations of these emulations, which in turn ... . Even if this is possible, it seems to raise in a new guise the spectre of the Eternal Return which Tipler is so keen to avoid. (Perhaps we can get something even more like the Eternal Return if we think about the real run times for the emulations. Isn't it the case that an event in an emulation of an emulation will be closer to the Omega Point than the same event in the emulation? Or is there some deep confusion in this thought?)

[29] It is probably worth pointing out that I have not discussed all of the assumptions which Tipler makes in setting our his full theory. Among the other assumptions which he explicitly makes, there are the following: (i) the second law of thermodynamics applies in all circumstances whatsoever (p.72); (ii) the 'Standard Model' and General Relativity are objectively true (p.89); the phase space of the universe must be infinite (p.101); (iv) the wave function of the universe is that wave function for which all phase paths terminate in a future Omega Point, with life continuing into the future forever along every phase path in which it evolves all the way into the Omega Point (p.181-see also p.3)) There are also various implicit assumptions, e.g. about the nature of quantum cosmology, and the consistency of General Relativity and quantum mechanics. It would take us too far afield to try to discuss all of this. (Perhaps it is also worth noting the assumptions of the No-Return Theorem, upon which Tipler's theory relies-see pp.102-3.)

[30] Dyson is the author of Infinite In All Directions (New York: Harper & Row, 1988) and "Time without end: physics and biology in an open universe" (Reviews of Modern Physics 51, 1979, pp.447-60), two charming discussions of possible futures for life in an open universe. Dyson showed the mathematical equivalence of the quantum electrodynamical theories of Schwinger, Feynman and Tomonga. Many people feel that he should have shared in their Nobel Prize. He was for many years at the Institute for Advanced Studies in Princeton. His autobiography -- Disturbing the Universe (New York: Harper & Row, 1979) -- is also a charming work.

[31] At p.172, Tipler writes: "Since the orbit of the Earth is chaotic, it is experimentally meaningless to speak of the past history of the Earth's orbit. The real past history of the Earth is the equivalence class of all histories which are consistent with what we know about the Earth's present position. ... The Earth's past history is really many histories." So perhaps Tipler would deny that individual atoms have histories. However, this is just another instance of the slide from epistemological considerations to ontological considerations (a.k.a. the application of a verificationist principle).

[32] Actually, it may not be entirely obvious that the China Brain is physically possible-there are delicate questions about physical laws and physical boundary conditions which may need to be addressed. After all, if we are supposing that each person is simulating a neuron, there is a question whether people are physically able to act quickly enough to perform the function of a neuron. (Remember, too, that each person must undergo some neuronal activity as part of performing their function.)

[33] At p.228, Tipler seems to say exactly the opposite: "[T]he question of whether two physical systems which differ in spatial or temporal location are to be identified is a question of physics, not philosophy." If two objects have different spatial location, then-setting aside bizarre speculations about bilocation (and irrelevant considerations about time travel)-they are not identical: there are two of them. However, as I go on to say in the main text, it seems clear that 'identification' for Tipler does not have its usual philosophical meaning.

[34] The following passage might be thought to make difficulties for my claim that Tipler conflates numerical identity and qualitative identity: "[I]f it is in fact possible for the physical universe to be in precise one-to-one correpsondence with a simulation, I claim we should invoke the Identity of Indiscernibles and identify the universe and all of its emulations, its perfect simulations. The 'Identity of Indiscernibles' is a philosophical rule introduced by .. Leibniz. .. According to this rule, entities which cannot be distinguished by any means whatsoever, even in principle, at any time in the past, present, and future, have to be considered identical. " (p.207) I take it that Tipler is interpretting the 'Identity of Indiscernibles' as a kind of verificationist principle: there are no (qualitative) properties which are indiscriminable even in principle. If two things can't be told apart even in principle, then there is no qualitative difference between them. However, I also suppose that most philosophers take the 'Identity of Indiscernibles' to be a quite different principle, to the effect that there cannot be two things which are qualitatively identical (a principle which Tipler himself denies).

[35] Very curiously, the Appendix for Scientists contains a section in which Tipler discusses two possible counter-examples to Church's thesis. The second of these possible counter-examples uses the structure of an Omega Point space-time in which there is time travel to finesse the construction of an infinity machine. I take it that this shows that he really doesn't think that there is any logical problem with the notion of a non-computable equation-and hence that he can hardly suppose that such a notion is meaningless. (For an interesting discussion of this kind of issue, see: J. Earman and J. Norton (1993) "Forever is a day: supertasks in Pitowsky and Malament-Hogarth spacetimes" Philosophy of Science 60, pp.22-42.)

[36] John Earman (1995) Bangs, Crunches, Shrieks, Whispers New York: OUP, p.207

[37] These issues are important for Tipler because of their bearing on his definition of eternal life: "I shall say that life goes on forever iff: (1) information processing continues indefinitely along at least one worldline g all the way to the future c-boundary of the universe (that is, until the end of time); (2) the amount of information processed between now and this future c-boundary is infinite in the region of spacetime with which the worldline g can communicate (that is, the region inside the past light cone of g); and (3) the amount of information stored at any given time t within this region diverges to infinity as t approaches its future limit (this future limit of t is finite in a closed universe, but infinite in an open one, if t is measured in what physicists call 'proper time')." (pp.132-3) Because of the importance which Tipler attaches to subjective time, he holds that life only goes on forever if there is an actual infinity of thoughts generated up to the end of time. ("A person who has thought ten times as much .. as the average person has in a fundamental sense lived ten times as long as the average person." (p.134))

[38] Tipler writes: "I've spent the past 15 years teaching myself [theoretical particle physics and computer complexity theory]. I've done it so you can do it." (p.395) Also: "We physicists are .. an extremely arrogant group of scholars. ... I not surprisingly share this arrogance. In my previous publications on religion and physics, I have attempted to conceal this arrogance (not very successfully). In this book, however, I have not bothered ..." (p.xiv) For myself, I didn't find anything to dislike about the tone of the book, or even about these remarks; they seem to me to be manifestations of an earnest innocence. (One qualification: Tipler's speculations about life in heaven-'improving' those with 'defects' like old age and Down's Syndrome (p.243); fulfilling the sexual fantasies of middle-aged heterosexual men (pp.257-9); and so on-are not very edifying. Other such gaucheries are interspersed throughout the book.)

[39] For some discussion of the intricacies, see B. van Fraassen (1995) "'World' is not a count noun" Nous 29, 2, pp.139-57; also G. Oppy (1997) "Pantheism, Quantification, and Mereology" Monist 80, 2, pp.320-36.

[40] Ellis, op. cit., claims that Tipler's deduction from his definition of 'living being' that an automobile is alive is 'a reductio ad absurdum of his entire method of argumentation'. It seems to me to be far more charitable to think that something has gone wrong with just this particular deduction.

[41] See D. Dennett (1984) Elbow Room Cambridge MA: MIT Press, for further details.

[42] At p.278-9: "Africans take religion very seriously. It has been said that in Africa people talk about philosophy and religion as Americans and Europeans talk about football. A Harvard professor of religion recently visited Ghana and was bombarded with theolgoical questions from clerks at the airport who were reading Bibles under their desks. So it is not surprising that Africans have developed a quite sophisticated theology." All that supports that final 'so' are the unsupported assertions of Ari Goldman. (You might also wonder about what is being claimed here. That all Africans take religion very seriously? That most do? That a great many do? Or what?)

[43] Consider this example: "Nietzsche's philosophy has had an enormous effect on twentieth-century culture. The existentialist philosopher Karl Jaspers has said that Soren Kierkegaard and Friedrich Nietzsche have between them determined the starting point of all twentieth-century philosophy." (p.81) Since Jaspers' claim is ludicrous-think, for example, of Popper and Ayer-it does nothing at all towards showing that Nietzsche's philosophy has been particularly influential. (Of course, I don't want to deny that Nietzsche has been influential; the point is just one about the quality of Tipler's argument for this claim.)

[44] Of course, Tipler means: the old word for computer science. The use/mention distinction is not one of his strong points, though it is perhaps pedantic to insist on it in contexts where no harm arises. (Also, there is perhaps some irony in the fact that Heidegger has quite a following amongst some groups of US cognitive scientists! Questions about Heidegger and Nazism seem to me to be very, very complicated.)

[45] Does Tipler really believe all of this? On what grounds? (Again, there is a question about implicit quantifiers which must be asked. Is he talking about all of the Japanese? Most? A great many? The ones that matter? Or what?)

[46] Another section which has something of the same character is "The Triumph of Progress", which discusses conceptions of progress in: Spencer, Engels, Haldane, Milne, Bernal, de Chardin, Dyson, Gould and Maynard-Smith. This section is rather more successful than the one discussed in the main text.

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