1) Scientists have increasingly become aware that the universe is ‘just right’ for life. If any one of a number of features of the universe had been even slightly different, life as we know it would be impossible.
2) For example, various features of the universe are ‘just right’ for the existence of stars, galaxies and life itself; had they been slightly different the human race could not exist. Had the ratio of the electromagnetic and gravitational forces differed by about 1 part in ten thousand billion billion billion billion then stars such as the Sun, which are capable of supporting life, could not exist.
3) If the strong nuclear force been weaker this could have resulted in the instability of elements necessary for carbon-based life, while if it had been stronger this could have had a negative impact on the production of carbon and oxygen. The existence of hydrogen is sensitive to the strength of the weak nuclear force. A decrease in the weak force would mean that there would be no hydrogen burning stars like the Sun.
4) Theism provides a very neat explanation for this fine-tuning. Fine-tuning is an example of the sort of order we’d expect to find in a universe created by God. God would have reason to bring about valuable things, like a community of embodied moral agents. We must compare God’s reasons for creating a fine-tuned universe with the absence of any reason for a finely tuned universe given atheism. Such a complex and valuable state of affairs is much, much more likely given theism than chance.
5) Some have objected that theism doesn’t provide a good explanation because we don’t know what sort of universe God would want to create. However, God and humans would have certain properties in common. Both are rational, both are agents, and -unless we wish to embrace moral scepticism - we should acknowledge that both would recognise similar values. We also know from observation and our own direct experience that rational agents bring about complex states of affairs that are ordered for some purpose (eg. machines) or that bring about some value (eg art). The complexity of our universe brings about great beauty and life is a valuable state of affairs. So fine-tuning seems much more likely given theism.
6) Some object that theism doesn’t provide a mechanism to explain how fine-tuning came about. However, many good explanations don’t provide a mechanism. Isaac Newton’s theory of gravity, for example, provided powerful explanations of planetary motion even though there was much disagreement about the mechanism by which one massive body exerted a force on another. The same applies in quantum theory; no-one really knows what’s going on, but quantum theory certainly explains a lot!
7) Some have objected that fine-tuning does not require an explanation. After all, if there was not a finely-tuned universe we couldn’t exist. And if we didn’t exist, no one would be around marvel at all the complex order in the universe. So, maybe we shouldn’t be surprised to discover that our universe has been finely-tuned; if it didn’t we wouldn’t be here to observe it! But this confuses two very different ideas. It confuses sentence (A) If human observers exist, it is inevitable that they will observe an ordered universe with sentence (B) it is inevitable that human observers exist. (A) is a rational belief, but (B) seems very implausible. Given all the ways our universe could have turned out, our existence seems extremely unlikely.
8 ) Yet another objection is to say that our universe is just one of many universes comprising a multiverse. This “multiverse hypothesis” requires sufficiently many universes with different physical constants so as to almost guarantee that at least one universe would be suitable for life. The idea is that all of these universes have different values for the constants and since there are so many of them (perhaps infinitely many) some happen to be suitable for life just by chance. Some prefer the multiverse hypothesis to theism because it seems more scientific. Yet it is difficult to see how we could observe or detect such multiverses.
9) Even if a multiverse theory eventually explained certain experimental results well, this could be outweighed by its much greater complexity. Consider, for example, Max Tegmark’s proposal that everything which can happen does happen somewhere in the multiverse. This means that there are multiple copies of you; in some universes you are taller, in some shorter, in some fatter, in some thinner, in some you are Prime Minister, in some you are the richest person on the planet. It’s difficult to think of a more complex, extravagant, counter-intuitive, theory.
10) Furthermore, even if a theory that was supported by evidence predicted a multiverse, we might wonder whether there is a simpler single-universe theory that can account for all the evidence without having to appeal to multiple universes. In that case, we might be tempted to accept the successful theory as a working hypothesis while remaining agnostic about its more extravagant claims.
11) Robin Collins points out that large, non-fine-tuned universes in a multiverse will contain “little islands of order” that assemble purely by chance. Many of these islands will have observers that have also assembled by chance. A multiverse will contain many such observers in its non-fine-tuned regions. In fact, in a multiverse there would be many more observers in the “little islands of order” than there are in our own finely tuned universe. So, the multiverse theory predicts observers both in finely-tuned regions and in some non-finely tuned regions. Indeed, most observers will exist in regions which have not been finely tuned.
However, such “little islands” of order would not exist for very long, and would be surrounded by an ocean of disorder. That’s not what we observe. We live in community of other rational observers (humans) with other embodied beings (animals) in a cosmos of exquisite beauty and order. These are not the observations that the multiverse theory would predict – it is much more likely that we would observe a “little island” of order and an ocean of disorder on the multiverse theory. So our observations confirm design over the “multiverse hypothesis”.
12) Remember, a”multiverse hypothesis” requires sufficiently many universes with different physical constants so as to almost guarantee that at least one universe would be suitable for life. This being so, a multiverse would just push design back to the level of the multiverse itself ; it would raise the question of how the multiverse came about in such a way as to make life inevitable. There are a number of reasons for thinking that such a multiverse would be more probable given design. One reason is that inflation theory, at present is a key component of favoured mechanisms for generating multiple universes, seems to require fine-tuning.
Robin Collins argues that the inflationary multiverse scenario requires a number of components to be in place, without any one of which it would still almost certainly fail to produce a single life-sustaining universe . These components are a mechanism to supply the energy needed for the bubble universes (the inflaton field), a mechanism to form the bubble universes, a mechanism to convert the energy of the inflaton field to normal mass / energy, and a mechanism that allows enough variation among the universes. In addition, he argues that appropriate background laws, such as gravity, and physical principles, such as the Pauli exclusion principle, would need to be in place to support life.