Why We are Fortunate to Live Here

If you want a fun physics book exploring the scientific basis for the claim that nature seems set up ahead of time for intelligent life, and also the philosophical arguments for why we may find ourselves living here – I can recommend “A Fortunate Universe.” Luke A. Barnes and Geraint F. Lewis are talented and passionate professors of Astronomy who both study the universe, and want to discuss the observation that it appears to be set up – or fine-tuned – for intelligent life. It’s not the universe that’s fortunate. Actually, it’s us!


The book starts here. The term “fine-tuning” does not imply or assume a creator of the universe. Rather, it implies the sensitivity of an outcome to input parameters or assumptions. Fine-tuning for life observes a contrast between a wide range of possibilities and a narrow range of outcomes that lead to life.[1] Their definition of “life” is a pragmatic one; “life is characterized by the capacity to grow, metabolize, actively resist outside disturbance, and reproduce.”[2] They also clarify that the universe’s physical laws have mathematical forms that only accurately predict natural occurrences when particular constant numbers are inserted into these equations. These constants, like electron mass and force strength, can’t be arrived at by theory, they can only be measured experimentally by scientists.

The Fun Stuff

The meat of the book, is an exploration of the implications of what would happen if natural constants and the laws they support were changed. With particle physics, the electron is fundamental, the proton and neutron are composed of different configurations of other fundamental particles, up and down quarks. Crucially, Barnes and Lewis observe fine-tuning in the properties of the members of this particle zoo. Change anything, life is not possible because chemistry and the periodic table are lost! What about natural forces? If you change the nuclear force holding atomic nuclei together, you are facing an uncertain universe where anything is possible. They also observe the beginning of the universe, pointing out the low entropy starting point. This means, much free energy was available for universe creation. But – it need not have been that way at all. There are many ways the universe could have been born, and so the wealth of free energy that must have been available at the start is surprising.[3] In summary, in these and other ways, they show our universe to have a particular initial state, and a set of life-permitting laws, masses, and forces that play out in three dimensions of space and one of time. “With so many potential ways the universe could have been, we cannot ignore the apparent specialness of our existence.”[4]

This book is a great resource. It goes beyond just saying that there is a narrow band within which the natural constants can be set for a life-permitting universe, and it actually shows what the universe might be like if each of these natural constants were different. Starting with particle mass, they move to forces and onto energy and entropy. Taking basic principles of physics and chemistry, they reveal how a life-permitting universe would easily be broken if each of these constants were adjusted. This lends further weight to the argument for fine-tuning because it tangibly demonstrates the narrowness of the life-permitting band in a convincing way.

Cool Question and Answer Session

Towards the end of the book, they switch gears. Chapter seven is a compendium of common reactions to fine-tuning, and the authors response to them. For example, one reaction observes the largely inhospitable nature of the universe. If the universe is fine-tuned for life, why is so much of it hostile to that life? They answer that inhospitable areas have nothing to do with the conditions on planet Earth. The phrase ‘life-permitting’ does not mean ‘crammed with living beings.’[5] Rather, it means the universe has some necessary physical conditions in particular locations. Even the vacuum of space, which is hostile to life, plays its part in making the universe life-permitting and a place where scientific discoveries can occur.[6]

Philosophical Answers to the question, “But Why?”

Yet my favourite chapter is the final one. Gears shift again, and Barnes and Lewis launch into a discussion together about the issues around fine-tuning. It is clear that, while Barnes prefers a theistic answer to fine-tuning, Lewis opts for the multiverse explanation. William Lane Craig has observed that the fact that they fundamentally disagree on this point gives their book an aura of open-mindedness and credibility.[7] I would add that it also makes the book a powerful tool for the Christian apologist who seeks to engage skeptics on these issues.

Theism is raised when Barnes states “there is another, older answer,”[8] for why fine-tuning exists. While theism is challenged by Lewis, Barnes does reply with a thoughtful exploration of the argument for evil and suffering, and I think it is wonderful to find this content in a physics book. Perhaps the readers who come for the physics may receive more than they were bargaining for. I hope many physics enthusiasts who are undecided on “THE G WORD!” are challenged to think more deeply. In the course of their discussion, they also touch on the fact that the universe is not just a physical construct, it is also an inherently moral one. A universe capable of producing and sustaining moral beings is one that God may create.[9] I agree with Tripp, who opines, “Barnes … challenge[s] atheistic arguments of the Richard Dawkins variety …a universe that tends toward living, moral agents is simply more likely with a God who is also a moral agent.”[10]

Lewis and Barnes also uncover the argument between naturalism and theism. While Lewis seems open to both options, Barnes clearly favors theism and presents solid arguments against the ability of naturalism to answer the big questions. Barnes reminds Lewis that the conflict is not between science and theism, but rather between naturalism and theism. The theist is no less rigorous a scientist than the hard naturalist, and the “success of science looks the same on naturalism and theism.”[11] But while the naturalist is left with a narrow interpretation of the scientific results, the theist has a much more open field available to him. To the naturalist, there is no explanation for the fine-tuning of the universe. Why would the naturalist expect to find simple equations that govern nature, combined with specific and significant constants which orient it for life? Surely on naturalism, the likelihood of any physical universe is the same as any other. There are no facts or explanations for why the universe is as it is, “there is nothing that explains the ultimate laws of nature.”[12] Yet Barnes concludes that theism naturally points to, and so explains, the tiny subset of possible habitable universes including our own. With God in the picture, it is more probable that a habitable cosmos would occur, over the infinite sea of uninhabitable universes across parameter space.[13] I appreciate their openness and feel they have encouraged me to more firmly point out the consequences of naturalism to the skeptic in my discussions.


This book is relevant for skeptics and Christian believers alike. It models healthy interactions between these two groups, and it guides the discussion through the important empirical and theoretical science of fine-tuning, as well as the philosophical resources available to explain it. It is strongly illustrated with graphs instead of complicated mathematics, and there are no spelling errors in the text. I felt that some of the scientific chapters became tougher going, and personally, I found their treatment of probabilities and Bayesian Theory quite challenging. Yet I think their brief introduction to these and other topics lays the groundwork for further learning. I strongly recommend this popular level physics book to the mainstream audience. While it may sometimes frustrate the professional physicist, I feel it does an excellent job of explaining the issues in the fine-tuning discussion. This is not simply a numbers game. The science points to fine-tuning, and there are rational philosophical approaches to understanding why this state of affairs exists.




[1] Geraint F. Lewis and Luke A. Barnes, A Fortunate Universe Life in a Finely Tuned Cosmos, (Cambridge: Cambridge University Press, 2016), kindle edition, 3.

[2] Ibid., 15.

[3] Ibid., 127.

[4] Ibid., 236.

[5] Ibid., 246.

[6] Ibid.

[7] William Lane Craig, Philosophia Christie, Volume 20, Issue 2, (2018): 596 – 599.

[8] Barnes and Lewis, 322.

[9] Ibid., 340.

[10] Jeffrey M. Tripp, “A Fine-Tuned Universe, or These Scientists Sound Like Theologians,” Religion & Theology 26, Issue 4 (October 2019): 562-567, accessed February 29th, 2020, https://onlinelibrary.wiley.com/doi/full/10.1111/rirt.13642.

[11] Barnes and Lewis, 336.

[12] Ibid., 335.

[13] Ibid., 343.

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I live in the UK, I'm married to Janet and I'm passionate about proposing a case for the historic Christian faith. You can find me on Twitter at @stuhgray.

2 thoughts on “Why We are Fortunate to Live Here”

  1. Excellent review. I’ve been meaning to get to this one. From a philosophical perspective the idea of God, a first cause, or intelligent designer is among the oldest positions and pre-dates Plato and Aristotle. I’m convinced from the fact of Being, that God must be a logical necessity, not a probability (as some apologists suggest). Anyway, thanks for the excellent post. Keep up the good work.

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