Review: A Fortunate Universe: Life in a Finely Tuned Cosmos by Geraint Lewis and Luke Barnes

Geraint F. Lewis and Luke A. Barnes, A Fortunate Universe: Life in a Finely Tuned Cosmos. Cambridge: Cambridge University Press, 2016. ISBN 078-1-107-15661-6.

Authored by a senior and a junior astrophysicist at the University of Sydney, this book is an open-ended exploration of the fine-tuning of the cosmos for embodied, living agents. Although both authors are convinced on the basis of the evidence that the universe is so fine-tuned, it seems, If one may judge by the imagined dialogue between the two authors in the final chapter, that Lewis, a secularist, favors the multiverse explanation of the observed fine-tuning, while Barnes argues for theism as the best explanation (pp. 344, 353). This disagreement gives the book an aura of open-mindedness and credibility.

Chapter 1 lays the groundwork for a discussion of the physical evidence for fine-tuning. Here we find a characterization of what is meant by “fine-tuning” (p. 4), along with related terms like “life” (pp. 10-15), “the anthropic principle” (pp. 15-21), and even “science” (pp. 21-27.) The claim is that various “free parameters” of the laws of physics—certain constants and boundary conditions—seem to be fine-tuned for life. “The claim is that small changes in the free parameters of the laws of nature as we know them have dramatic, uncompensated and detrimental effects on the ability of the Universe to support the complexity needed for physical life forms” (p. 29).

This claim is supported in detail in chapters 2-6. Chapter 2 surveys particle physics, showing how finely-tuned sub-atomic particle masses are. Chapter 3 treats the four fundamental forces of nature. Chapter 4 is about thermodynamics, particularly the second law concerning entropy increase, which reveals the incomprehensibly fine-tuned low entropy condition of the very early universe. Chapter 5 discusses the expansion of the universe, including the famed cosmological constant, one of the most dramatic examples of fine-tuning. Chapter 6 is a discussion of nature’s symmetries, including the asymmetry of time (time’s arrow) and the 3-dimensionality of space. These chapters, the meat of book, are a wide-ranging survey of contemporary physics, written at a level the intelligent layman can understand.[1] They are testimony to the breath-taking achievements of contemporary science and of the awesomeness of the universe in which we live.

What makes this part of the book different from many other works on fine-tuning is the degree to which Lewis and Barnes explain the physics of fine-tuning. They are not content merely to boggle our minds with incomprehensible numbers such as the fine-tuning of the proton/neutron mass ratio to one part in a jillion (indeed, I should say that this part of the book suffers from understatement, if anything). Rather they explain how the proton mass is a function of the quark masses, and these in turn of the Higgs field, and this in turn, perhaps, of supersymmetry. The reader’s understanding of fine-tuning is deepened, and he comes to see that at every level fine-tuning appears.

Lewis and Barnes conclude this part of the book with the words:

Our conclusion is that the fundamental properties of the Universe appear to be fine-tuned for life. We need a cosmos that expands not too fast and not too slow, that forms structure, with a mix of stable elements that can form stars, planets and cells, with the right mix of forces for stars to burn for billions of years, with plenty of carbon and oxygen, with a low-entropy past and free energy into the future, with a life-supporting number of dimensions, and even with mathematically elegant and discoverable laws. Such a cosmos is a rarity among our Universe’s cousins and distant relatives (p. 290).

Seen in this light, the title of the book is something of a misnomer: the universe is not fortunate; we are! In the authors’ own words, “we should feel pretty fortunate to be in a universe that can sustain us!” (p. 292). A Beneficent Universe might have been a more accurate title.

It is at this point that for me, as a philosopher, things get really interesting. Chapter 7 responds to “A Dozen (or So) Reactions to Fine-Tuning,” ranging from the banal (“Most of the universe is inhospitable to life!”) to the sublime (“Whence the probabilities?”). In this and the final chapter the authors discuss the philosophical issues that surround fine-tuning. The handling of these issues displays Luke Barnes’ philosophical sophistication. Barnes is thoroughly familiar with the work of analytic philosophers on these issues and has interesting contributions to make to the discussion. Indeed, one of my frustrations with these two chapters is that because they are written in the same layman-friendly style as the rest of the book, I often had the sense that beneath the casual conversation, some very profound points were being made, but I was not sure exactly what they were. I find more helpful the sort of clarity with which a philosopher like Robin Collins handles these issues.

For example, many of the reactions to fine-tuning discussed in chapter 7 are really attempts to explain fine-tuning as the result of chance, not denials of fine-tuning as defined above, which says nothing about the probability of fine-tuning. One could admit that the free parameters cannot be significantly changed without rendering the universe life-prohibiting and yet maintain that this is just the result of chance. So when someone responds, e.g., “This universe is just as unlikely as any other universe” (p. 351), is not the proper response, “That is not an objection to the fact that our universe is fine-tuned for life. It’s the claim that the fine-tuning is due to chance: we’ll consider that claim when we discuss how the fine-tuning is best explained”? Lewis and Barnes argue that it makes sense to assess the probability of fine-tuning, given mathematical knowledge and knowledge of nature’s laws without knowledge of the values of the free parameters, and that this probability is so low that chance is not a good explanation when compared to alternatives (p. 286).

The book’s final chapter takes up the “why” question: why is the universe fine-tuned for life? The options are (i) a deeper physics will reveal that the parameters are not really free after all (physical necessity), (ii) the multiverse guarantees the existence of a finely-tuned universe, which is the only kind we can observe (chance); (iii) a cosmic designer intended the universe to permit life (theism). Barnes is surprisingly open to (i), though he ultimately argues against it (pp. 345-6). He presents the usual objections to (ii), including the threat posed by the dreaded Boltzmann Brains (an objection Lewis never answers). Most interesting is Barnes’ defense of (iii). I must confess that in a book so wholly about physics and so open to there being unknown physical laws that will explain the fine-tuning, I feared that the introduction of the Designer hypothesis would come across as a Deus ex machina that had no proper place in discussions of this sort.

But Barnes really pulls off well the introduction and defense of theism. He says, “There is another, older answer.” To which Lewis exclaims, “I know where this is going! THE G WORD!” (p. 323). This exclamation accurately expresses the attitude of many physicists. Interestingly, Barnes does not plunge immediately into an argument for theism based on fine-tuning. Rather he takes an indirect route: he begins with a long discussion of the cosmological argument from contingency (pp. 323-39). He contrasts theism with naturalism, which denies that there is any explanation of the ultimate scientific laws and the physical phenomena which follow from them. He emphasizes that it is naturalism, not science, that is the alternative to theism, and it explains nothing. That sets the table for the introduction of an argument for theism from fine-tuning (p. 339). A finely-tuned universe is much more probable on theism than on naturalism. That raises the issue of what has been called ”divine psychology”: why think that God would create a finely-tuned universe? Barnes argues on the basis of the goodness of God that He would not be unlikely to create a universe suitable for the existence of embodied, moral agents, and that suffices to neutralize the objection.

Barnes summarizes his case as follows (p. 344):

1. Naturalism is non-informative with respect to the ultimate laws of nature.

2. Theism prefers ultimate laws of nature that permit the existence of moral agents, such as intelligent life forms.

3. The laws and constants of nature as we know them are fine-tuned–vanishingly few will produce intelligent life forms.

4. Thus, the probability of this kind of universe Is much greater on theism than on naturalism.

Barnes does not allow theism to have the final word in the book. By considering the outlandish hypothesis that we are but simulations in some physicist’s computer, Barns actually increases the credibility of theism, which looks modest by comparison.

The book is attractively printed and contains almost no printer’s errors. I highly recommend it for students of fine-tuning.

• [1]

  Those who undertake the difficult task of scientific popularization too often think that this involves trying to connect with one’s readers by showing oneself to be a cool guy, rather than the scientific nerd we all figure the author to be. Accordingly, Lewis and Barnes’ book is filled with ”cutesy” comments about pop culture, movies, and entertainers. Mercifully, most of these remarks are confined to the footnotes, as is this minor complaint.

  Those who undertake the difficult task of scientific popularization too often think that this involves trying to connect with one’s readers by showing oneself to be a cool guy, rather than the scientific nerd we all figure the author to be. Accordingly, Lewis and Barnes’ book is filled with ”cutesy” comments about pop culture, movies, and entertainers. Mercifully, most of these remarks are confined to the footnotes, as is this minor complaint.