God and the Multiverse: Scientific, Philosophical, and Theological Perspectives
Reviewed by Kent Dunnington, Philosophy and Religion, Greenville College
The ideas in God and the Multiverse are important for thinking Christians to consider, but this book is written at a high level of specialization and picks up in the middle of a scholarly conversation. The conversation is about whether we have good reasons to think we live in a multiverse, that is, a world populated by more than one universe, possibly infinitely many. By “world,” the authors mean everything that exists. By “universe,” the authors mean something like “a spatiotemporally interrelated, causally closed aggregate” (129). Our universe includes everything in our space-time continuum, but our world may include more than this; it may include other universes; it may be a multiverse.
Interest in the multiverse comes from two sources: science and philosophy. The most common scientific arguments for a multiverse are connected to cosmic inflation and quantum mechanics. In his Introduction, Klaas Kraay states that the essays in this volume are not about the science surrounding the multiverse thesis. This is accurate. Although the first two chapters are written by physicists, I have little more understanding than I did before reading the book of the scientific evidence in favor of the multiverse, or even of the extent to which what scientists mean by “multiverse” overlaps with what philosophers mean.
Philosophical speculation about the multiverse is not new, but it has increased in opposition to the fine-tuning argument for God’s existence. This argument begins from the observation that many of the physical laws and constants in our universe appear to be improbably “fine tuned” such that slight variation in any one of them would make our universe inhospitable to sentient life. According to the fine-tuning argument, the existence of an intelligent designer is the best explanation of this improbability. The argument is perceived by many contemporary non-theists as the most formidable theistic argument. (A few years ago the notable atheist philosopher Antony Flew was converted to theism by a fine-tuning argument.) In response, non-theists argued that the multiverse thesis undermines the fine-tuning argument. If our universe is only one of many, then the apparent fine-tuning of our universe is no longer improbable. Make the sample of universes large enough and no physically possible universe is improbable. So there is an equally probable atheistic explanation of apparent fine-tuning.
It appeared the sides were clearly drawn: non-theists should accept the multiverse thesis, theists should reject it. But as Klaas Kraay explains, today it is no longer clear what side theists should take: “In recent years, however, several philosophers of religion have independently suggested that, far from being hostile to theism, multiple universes are just what we should expect to find if God exists. This volume collects together twelve new essays that address this issue” (3). To understand the essays in this volume, you have to be familiar with those earlier proposals. Specifically, you have to understand why some theistic philosophers think the multiverse provides a response to the problem of evil.
Here are three tightly connected questions that arise for the theist on the presupposition that our universe is coextensive with the world. First, why would an omnibenevolent God create this world given there is clearly a better world God could have created, for instance a world in which there is one less fawn burned in a forest fire. Second, on the assumption that an omnibenevolent God would create the best possible world, is such a notion even coherent? It seems we can imagine an infinitely ascending chain of worlds, each of which improves on the previous, perhaps by including one more on-balance happy person. And third, if such an ascending chain is possible, how could an omnibenevolent and rational God choose which to create? It appears any choice God makes will be arbitrary and thus violate the so-called “principle of sufficient reason.”
The multiverse is attractive to theists because it looks like it can resolve each of these interconnected problems. Imagine the world is not coextensive with our universe. Imagine the world includes multiple universes. Imagine that in creating the world God actualized every possible universe that met some threshold of overall value (trying to specify what this threshold would be is one challenge for theistic multiverse theorists). In such a world, we can say that although ours is not the best possible universe, it is a universe that must exist as part of the best possible world, since such a world will necessarily include all the universes that meet the relevant value threshold. And, we can grant there may be no such thing as the best possible universe. There may be an infinitely ascending chain. No problem, God can actualize all members of the chain above the relevant threshold. And this removes the worry about the principle of sufficient reason. God need not arbitrarily choose one universe to actualize. He actualizes all of them above the clearly non-arbitrary value threshold.
Most of the essays in this volume are about whether the multiverse really can resolve these problems, or whether, if it does, the theoretical costs are too high. To give just one example, Michael Schrynemakers argues that a multiverse so envisioned, even if it solves the problem of evil, does so at the cost of common sense notions of divine providence. For instance, we think God providentially acted to make David king. To say God providentially acted means God could have done otherwise. But if God could have done otherwise, there are possible universes in which God does otherwise. But presumably some of these possible universes meet the relevant threshold of overall value for inclusion in the best possible world. If these universes are actualized, what does it mean to say “God might have chosen not to make David king?” Notice that if these alternate universes are actual, the several people called “David” who were not made king in them cannot be the same person as the David that was made king in our universe. And if this is the case, then we lose our grip on what it means to say that God could have governed our universe differently. For these other universes are not instances of “our universe governed differently”; they are just different universes.
As this example suggests, the essays in the volume are highly abstract, often depending on our modal intuitions, that is, our intuitions about what is possible and what is necessary. We are in highly speculative territory here, and the authors of this volume do not shy away from such speculation.
As someone not heavily invested in this debate, my takeaways from the book concern the benefits and dangers of metaphysical speculation in Christian thought generally. As for the benefits, such speculation provides occasion to discover how the central doctrines of Christianity are compatible with a bigger and stranger world than the one we typically imagine. This is true of the final two essays in the volume, the first by Robin Collins, the second by Timothy O’Connor and Philip Woodward, both of which suggest that certain understandings of the doctrine of the incarnation are more compatible than others with a multiverse that may include multiple incarnations.
As for the dangers, much of the speculation is theologically heterodox. Two chapters are on how multiverse theories may or may not support pantheism. More concerning is speculation insufficiently constrained by moral caution. For example, consider Don Page’s speculative response to the problem of evil:
If there is an all-knowing God who is completely aware of the entire universe He creates and fully appreciates the mathematical beauty of its laws of physics that He uses in His creation, this omniscient conscious awareness could have enormous value and help make the entire world, including God and His own sentient experiences, the best possible world….Cancer and earthquakes may be logical consequences of these laws of physics. God Himself may grieve over the evils that are a consequence of the laws of physics that give Him even much greater joy, but there may be this inevitable trade-off. (53)
This is a response to the problem of evil as novel as it is morally repellent. Kant famously asked whether there are metaphysical foundations to morals, but an argument like this raises a different question about the relationship between morality and metaphysics, namely, are there moral bounds to metaphysical speculation?
So what side should theists take if the multiverse undercuts fine-tuning arguments but also offers promising responses to the problem of evil? Can theists have it both ways? Jason Megill’s chapter, by my lights the clearest and most interesting in the book, is the only one that addresses this question. Megill argues that theists should support a “restricted” multiverse, one that is big enough to solve the problems theists want it to solve, but not so big that it satisfies the atheist’s requirements for undercutting fine-tuning arguments.