I am a huge fan of David Deutsch’s writings. I loved both The Fabric of Reality and The Beginning of Infinity: Explanations that Transform the World. In fact, I loved them so much I took his bibliography and the back of each book (particularly the “Everyone Should Ready These” section) and started reading them. Deutsch’s worldview is so optimistic, it’s hard not to love it. I want to feel I can agree with Deutsch entirely, but felt I couldn’t without first seeking out the very best criticisms of his views.
So I sought out criticisms of Deutsch, starting with Roger Penrose, then moved on to others. 
In many cases, I just couldn’t find good criticisms. For example, Penrose’s views that computers can’t be minds simply didn’t hold up to Deutsch’s arguments. And though I found the Many Worlds Interpretation of Quantum Physics troubling, I have yet to find a single good criticism of it.
However, after researching his views on and off for a few years, I think I’ve come to a set of criticisms that (at least as of today) seem valid to me. I am going to do a series of posts explaining these criticisms. I’m hoping that my criticisms of his views will ultimately fail because I want to be able to accept his optimistic worldview. But I’ll need help understanding what is wrong with the criticisms I’m going to offer.
The Omega Point
My first criticism is of how Deutsch handles a certain aspect of Tipler’s Omega Point, namely whether or not the Omega Point would imply a ‘resurrection’ or not for those of us living now into it in the far future.
The Omega Point is a theory that Deutsch advocates at the end of The Fabric of Reality (in Chapter 14) and then rescinds in The Beginning of Infinity (p. 451).
Without getting into too much detail, Tipler’s Omega Point is that the universe will eventually contract to an infinitely small size (i.e. a singularity) and than pop out of existence. However, since there are an infinite number of computations that take place as this happens (with the computations speeding up over time until they are infinitely fast), any life that exists inside the Omega point will therefore experience an infinite life.  Admittedly, this result seems very paradoxical — why would causing a universe to disappear cause life to seem to go on infinite? But both Tiper and Deutsch demonstrate that this is the nature of infinite computation. 
Deutsch did later rescind his support for the Tipler’s Omega point, however, Deutsch continues to believe in the growth of infinite computation, and thus the existence (across the multiverse anyhow) of infinite life. (Infinity, p. 451)
Further, the arguments I’m about to question are not really tied to the Omega Point cosmology specifically. They will apply to any form of growing infinite computation that allows for life to never die out.  There for I’m going to use the terms “Infinite Computation” and “Omega Point” interchangeably because I believe Deustch, while no longer believing specifically in the Omega Point, does seem to still believe in something equivalent to it that makes it possible for life to exist forever and for knowledge to forever grow. 
Tipler’s vs. Deutsch’s: Will the Infinite Computation Exist in All Universes?
At the time Deutsch wrote The Fabric of Reality he agree with Tipler on many aspects of the Omega Point and disagreed on others. Deutsch agreed with Tipler on the idea that the Omega Point cosmology implied that life could live forever and never had to die out and that the growth of knowledge could continue forever.
However, Deutsch is some what less convinced than Tipler that, the Omega Point must take place and life won’t die out. (For Tipler’s argument that is must exist in all real universes, see The Physics of Immortality, p. 212–216) Deutsch argues that it is not clear that a ‘universal computer’ (i.e. an infinite computation) must exist in our universe rather than in just some universes (and thus not necessarily ours.) However, Deutsch favors the view that an such an infinite computation will exist in all universes. 
Tipler’s vs. Deutsch’s: Is the Infinite Computation God?
A bigger disagreement between Deutsch’s and Tipler’s views of the Omega point is whether or not the Omega Point should be considered ‘God.’ Tipler sees this final infinite computation as being Omniscient, Omnipresent, and Omnipotent, thus Tipler believes the Omega point is equivalent to beliefs about God.
Deutsch, on the other hand, points out that while in a sense one could think of the Omega Point as Omniscient, Omnipresent, and Omnipotent, that it would only be in a limited sense (limited by the laws of physics) and thus wouldn’t match current theology about the meaning of those words. 
My main concern isn’t whether or not we should apply the label “God” to an Infinite Computation. However, I feel this is important context to understanding the main question from Deutsch that I’m going to criticize.
Tipler’s vs. Deutsch’s: Will there be a Resurrection for Us Today?
In my view, the most important difference between Tipler’s and Deutsch’s views of the Omega Point (and thus for infinite computation) is whether or not it implies that there must be a resurrection of the dead for all of us alive today.
Now obviously, if we all will be resurrected into the infinite computation at the end of time, that makes a theory like the Omega Point theory far more personal. Frankly, I’d really like to know if our current best cosmological theories do or do not imply that, after I die, I will live again or I won’t. In short, Tipler and Deutsch disagree over whether or not the Omega Point (or any growing infinite computation) implies the existence of an afterlife.
Tipler believes that the Omega Point theory does imply the existence of an afterlife. His book, The Physics of Immortality, is specifically about this. It’s the part of the theory he’s most interested in. (Thus the name of his book.)
Deutsch, on the other hand, admits that while it is possible that an infinite computation could create an afterlife for us, that we don’t necessarily know that it will.
…Tipler points out that a sufficiently advanced technology will be able to resurrect the dead. It could do this in several different ways… Once one has enough computing power… one can run a virtual-reality rendering [i.e. a simulation] of the entire universe — indeed, the entire multiverse — starting at the Big Bang, with any desired degree of accuracy. … To the omega-point computers, nothing is intractable. (Fabric, p. 357, emphasis mine)
Deutsch goes on to say that this simulation of the omega-point past could eventually render us alive today to any level of accuracy. (p. 357) He notes that:
The controlling program can look out for these intelligent beings and, if it wants to, place them in a better virtual environment — one, perhaps, in which they will not die again… (Fabric, p. 357, emphasis mine.)
So while Deutsch agrees with Tipler that it is physically possible for an infinite computation like the Omega Point to resurrect us from the dead and create an afterlife for us, he seems to doubt that this will necessarily happen. (Thus creating yet another difference between an infinite computation and a traditional concept of “God.”) Deutsch goes on to make an argument to explain why he has some doubts:
The whole story about what these far-future intelligences will or will not do is based on a string of assumptions. Even if we concede that these assumptions are individually plausible, the overall conclusions cannot really claim to be more than informed speculation. (p. 358)
Then Deutsch attempts to clinch his argument by illustrating why Tipler’s beliefs about the Omega Point resurrecting us is isn’t a reliable speculation:
As a warning against the unreliability of even informed speculation, let me revisit the ancient master builder… with his pre-scientific knowledge of architecture and engineering. We are separated from him by so large a cultural gap that it would be extremely difficult for him to conceive a workable picture of our civilization. But we and he are almost contemporaries in comparison with the tremendous gap between us and the earliest possible moment of Tiplerian resurrection. Now, suppose that the master builder is speculating about the distant future of the building industry, and that by some extraordinary fluke he happens upon a perfectly accurate assessment of the technology of the present day. Then he will know, among other things, that we are capable of building structures far vaster and more impressive than the greatest cathedrals of his day. We could build a cathedral a mile high if we chose to. And we could do it using a far smaller proportion of our wealth, and less time and human effort, than he would have needed to build even a modest cathedral. So he would have been confident in predicting that by the year 2000 there would be mile-high cathedrals. He would be mistaken, and badly so, for though we have the technology to build such structures, we have chosen not to. Indeed, it now seems unlikely that such a cathedral will ever be built. … He would have been wrong because some of his most unquestioned assumptions about human motivation have become obsolete after only a few centuries. (p. 358–359)
Whew! That took a while but we’re finally there. This last passage is what I’m going to criticize as being a contradiction to Deutsch’s other beliefs throughout the rest of his books.
Criticism of Deutsch: Infinite Computation Implies Resurrection
I’m now going to use Deutsch’s own beliefs to demonstrate why I believe Deutsch must be mistaken in that last passage. And in doing so, I’m going to demonstrate that Tipler is correct that an infinite computation across a multiverse does in fact imply that we will all be resurrected and live forever, though only if Deutsch’s beliefs are correct. 
So here is my argument:
Deutsch’s Assumption 1: The quantum multiverse is real and anything that physically can happen will happen somewhere within the multiverse.
Deutsch’s Assumption 2: All life, including all of us reading this post, are really just computations that exist across an infinite number of realities in the multiverse.
Deutsch’s Assumption 3: It is physically possible for life to live forever and to grown their knowledge forever. Nothing in out best theories of physics denies this possibility. 
These three assumptions seem like very safe interpretations of Deutsch (as well as Tipler). They strike me as something like the most basic principles he’s arguing for. If I’m misinterpreting him on one of the above assumptions, then clearly my belief that he’s mistaken is itself mistaken.
However, if I’m correct that he is arguing in favor of all three assumptions, I just can’t see how Deutsch’s argument, in my last quote, can possibly be correct.
To be clear: Assumption 1 argues that anything that is physically possible will happen somewhere in the multiverse. And Assumption 3 argues that there will be an infinite growth of knowledge forever somewhere in the multiverse. Meanwhile, Assumption 2 makes it clear that given a growth of knowledge (and computation) in the far future, it is physically possible to resurrect us.
By Assumptions 2 and 3: It’s possible for us to be resurrected somewhere in the multiverse.
By Assumption 1: Anything that can physically happen will physically happen.
Therefore: By deductive logic, it must (given these assumptions) be the case there will be a resurrection that includes us alive today in this universe.(Though we’ll not necessarily be resurrected into this universe.)
That we might be resurrected into a different universe doesn’t really matter, as far as I can tell. This seems to be the only difference that Tipler and Deutsch can be allowed given their beliefs. Both must, of necessity, admit that a multiverse that contains every possible version of the Omega Point (or of any type of Infinite Computation) must contain versions of us after our deaths.
I just can’t see a way around this logic. What am I missing here? How does Deutsch’s argument about the ancient builder, and possible misunderstandings about the future motivations of people, have anything to do with it?
Sure, maybe across many universes there never is a group of people that feel motivated to resurrect us. But all that is required is that someone in the multiverse does. And this is guaranteed to happen in the multiverse somewhere. Even if 99.99999999999% of the multiverse had zero interest in resurrecting us, it wouldn’t matter. We’d be resurrected into that last sliver. And we’d live forever in it (if it has an infinite computation.) 
So I offer this as my first criticism of Deutsch, namely that he made an argument that seems to be mistaken given his own point of view. I admit this one isn’t really a very big deal by itself. I doubt Deutsch will care much if he had to conceded that, yes, in fact his view do imply a resurrection of the dead. That would be a good thing, right? It would improve his views, not make them worse. And perhaps one might even argue that his point is still valid for other things Tipler says, if not this specific issue. (And I would agree with that.)
But I have more fundamental criticisms of Deutsch to address in the future that are more concerning to me. So we’ll use this easier one as our starting point.
 Deutsch specifically mentions Penrose as being at odds with him in The Fabric of Reality. That’s why I started with Penrose as criticisms of Deutsch.
 Both Tipler and Deutsch demonstrate that the idea that this is impossible for life to exist inside is not true through out their respective books. See The Fabric of Reality and The Physics of Immortality.
 See Fabric, p. 352: “Subjectively, they will not be at the final stages of their lives but at the very beginning. They will be in no hurry, for subjectively they will live for ever.”
After studying this more deeply, I do now buy Deutsch’s arguments that life is really a certain kind of computation and that an infinite computation (such as one in a singularity) would therefore be equivalent to infinite life. However, if you don’t personally buy that argument, it won’t matter for this post. I’m just pointing out that there is a bit of a contradiction in Deutsch’s own arguments. So what matters here is that Deutsch accepts this is true, not that you personally do.
 I have a later criticism where the word “growing” becomes important. But it won’t impact this post.
 Deutsch says:
Or, to put that another way, will someone necessarily succeed in creating an omega point in our universe? This depends on the fine detail of the Turing principle. It says that a universal computer is physically possible and ‘possible’ usually means ‘actual in this or some other universe.’ Does the principle require a universal computer to be built in all universes, or only in some — or perhaps in ‘most’? We do not yet understand the principle well enough to decide. (emphasis in original, see Fabric, p. 353)
In Fabric, p. 354, Deutsch goes on to confirm that he feels that, at least for now, the formulation that a universal computer will exist in all universes is the more natural choice.
 In Fabric, p. 355–356, Deutsch points out that the Omega Point doesn’t even actually exist as a physical entity but is really just the limit of knowledge of all finite intelligent beings over time. Thus it’s omniscience is limited to the infinite knowledge created by those intelligent beings and can’t include things like “Cantgotu environments” which are VR simulations that can be proven to be impossible to instantiate under the laws of physics. How also argues that the Omega Point’s omnipresence is limited to be only after a certain date, and that it’s omnipotence is limited by the available matter and energy and the laws of physics.
I agree with Deutsch that the Omega Point certainly doesn’t fit any currently existing theological viewpoint on God and that Tipler is constantly overreaching to make the connection.
However, in Tipler’s defense, I think the ‘theological’ viewpoint of many Trans-humanist does fit this understanding of ‘God.’ The word “God” is definitely vague enough to fit many possible conceptions, including Tipler’s. But I’ve long believed that Tipler has little hope of ever convincing the Christian Church as a whole that his beliefs about God match theirs.
 To be clear, I am not arguing that Tipler is correct an infinite computation is equivalent to God, that God exists, or any of that which Tipler advances. I just included those beliefs of Tipler for what I felt was needed context. I am not even arguing that an infinite growing computation is a real thing. I am only at this time arguing that Infinite Computation (if real) + Multiverse (if real) => future resurrection for us alive today and that we’ll live forever somewhere in the multiverse. But only if those two assumptions prove true.
 I will later challenge if this assumption is even correct in a future criticism of Deutsch. But for our purposes today, I’m accepting it as true.
 I would also note that Deutsch’s assertion that we’ll probably never build a mile high cathedral, must be equally false. If an infinite computation exists across a multiverse where every physically possible thing happens, when he’s wrong. Of course a fair reading of Deutsch is that he’s merely saying that it won’t happen in this one universe, which might be correct.
My point here, however, is that he’s making a categorical mistake thinking that his argument makes sense across the entire multiverse. This is true of both his argument against a resurrection and the mile high cathedral. Both only make sense across a single universe. But when it comes to a resurrection from the dead, there is no reason to care about what happens in only one single universe, as far as I can tell. So long as you’re resurrected in some universe you are really and truly resurrected.