Sceptics have sometimes attempted to explain away the evidence for a designer by asserting that we live in an infinitely large multi-verse. If the laws of nature which govern our universe had different physical constants, or if the initial conditions of the universe been slightly different, stars, galaxies and life would have been impossible. The odds of a universe which is fine-tuned for life are extraordinarily low; however, if an infinite number of universes is somehow generated, a finely-tuned universe will appear by chance alone.
The argument runs that we should not be surprised that we observe a finely-tuned universe.The fact of our being restricts the characteristics of the kind of environment in which we find ourselves. This selection principle, it is alleged, necessarily restricts the existence of observers to finely-tuned regions of the multiverse. And physical infinities and chance explain the existence of finely-tuned regions of the multiverse.
However, it is not at all clear that observers could only exist in finely-tuned regions of the multiverse. A multiverse would contain “fluctuation observers” who come into being through the localised random collision of atoms. Each would be a single, isolated observer with just enough structure to have conscious experiences. The probability of such an observer assembling by chance in one region of the universe is astronomically low.
Simply put, given the probabilistic resources of an infinitely large multiverse there will be many more “fluctuation observers” in the multiverse than observers living in solar systems. This is because fluctuation observers can exist in universes which have not been finely tuned for life: for example they could fluctuate into existence in the many universes with cosmological constants too large for stars or galaxies to form.
Granted, finely tuned universes can contain many more observers than a non-finely tuned universe. However, the low probability of a fine-tuned universe compared with a non-fine-tuned universe would completely swamp the fact that fine-tuned universes contain more observers. This causes a problem for the “selection principle”: the vast majority of observers in a multiverse would be fluctuation observers.
Indeed, any observer selected at random from the multiverse is much more likely to be a fluctuation observer than an observer living on an hospitable solar system. The selection principle does not guarantee that observers will live in finely-tuned universes. So it does not explain our observation of a finely-tuned universe.
Put that another way: suppose our universe is infinitely large. We still have to ask ‘is this infinite universe governed by design or chance?’ So imagine two infi nite universes, one created by God and one governed by chance. Which universe will contain more complex order? Obviously, the universe which God governs!
While a small fraction of an infinite universe governed by chance will be ordered, the greater part will be chaotic. A universe governed by God would be ruled by a rational and creative agent, so it will be characterised by order, and contain many more examples of apparent design. The more complex order we observe, the greater the probability that we live in a universe which has been designed.
A small region of order is all that is required for the existence of humans; but we do not observe a small sea of regularity surrounded by an ocean of chaos; we observe an abundance of order wherever we look. So, even if our universe is infinitely large, our observations support theism and not atheism.
There are other difficulties for the multiverse objection. The hypothesis of an infinitely large multi-verse is compatible with just about any observation. In an infinite universe governed by chance, every physically possible event occurs sooner or later. If a message formed in the clouds stating ‘God exists. Repent and believe the Gospel!’ the atheist could simply reply ‘well, the universe is vast, maybe infinitely so. So sooner or later, on some planet or other, clouds were bound to take on that shape!’
The problem is 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.
In fact, the hypothesis of an infinite multiverse cannot even avoid absurdities and paradoxes. While an actual infinite is logically possible, it is not at all clear that an actual infinite could exist in nature. The mathematician David Hilbert conceived of a hotel with infinitely many rooms. The hotel could be filled to capacity; yet one can make room for infinitely many more guests by asking the guest in room one to move into room two, the guest in room two to move into room four and so on. All the odd numbered rooms will be free, leaving enough room for infinitely many more guests. This sort of paradox leads some to conclude that infinitely many things cannot exist simultaneously in nature.
Not all multiverse theories necessarily posit an infinitely large multiverse. When considering multiverse theories in general, we should keep in mind that 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.