Fine-tuning argument for God
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- philosophy
According to current, and very well-established, scientific theories, the behaviour of the universe is described by a set of fundamental constants. These constants cannot be calculated theoretically, they can only be determined by making measurements in the real world. Some common examples of such constants are:
- The mass of an electron.
- The speed of light.
- The gravitational constant - this constant relates gravity to mass, so for example it describes how strong the force of gravity is on the Earth given the mass of the Earth.
There are 22 fundamental constants in total. Although some of these constants have been known for a long time, many of them relate to either relativity or quantum theory, which have only been known since the early 20th century.
The basis of fine-tuning
The models physicists use to describe how the universe behaves depend on these fundamental constants. Of course, some scientists have speculated about what the universe might have been like if any of these constants had taken different values. That is just natural curiosity.
The result is, arguably, quite surprising. It appears that, if certain constants had been even a tiny bit different, then the universe would have been a very, very different place - quite possibly a place without humans.
Life as we know it depends on many things, but two key things that are required are:
- The possibility of complex chemicals such as carbohydrates, amino acids, and nucleotides.
- A suitable environment that remains stable for a very long time. In particular, liquid water appears to be essential, and it only exists in a very narrow temperature range. It took billions of years for life to evolve on Earth, and liquid water needed to be present for that entire period.
Fine-tuning appears at very small and very large scales. At the smallest scales, the strong nuclear force describes how protons and neutrons fuse to form atomic nuclei. If it were slightly weaker, protons and neutrons would never fuse, so chemical elements other than hydrogen could not exist, and therefore complex chemicals could not exist. If it were slightly stronger, protons and neutrons would fuse more readily to create heavier elements. This would mean that hydrogen might be quite rare, which would also mean very little water would exist.
The gravitational constant is important to the formation of stars. If it was too weak, stars could not have formed. If it was too strong, the universe would have been too energetic and stars would not have survived. Stars are important for two reasons. First, of course, the Sun provides the heat that keeps the Earth at a suitable temperature for life. But also, nuclear reactions inside stars convert hydrogen into heavier chemicals that are required for life. Most of the chemicals on Earth, other than hydrogen and helium, were formed within stars.
The cosmological constant is a constant that, in effect, controls the rate of expansion of the universe. If it had been larger than it appears to be, the universe would have expanded too quickly for stars to form, which would have made life as we know it impossible, as we have just seen. Some Christian apologists claim that this constant needed to be almost exactly what it is, to within 1 part in 10^60, otherwise life would have been impossible. However, it is not clear where this claim comes from. The science around the cosmological constant is still quite undecided, and the idea of calculating the probability of the universe being different is problematic, as we will see.
It is difficult to imagine, but even the number of dimensions in our current universe is a property of the universe. Perhaps the universe could have been formed with four or more spatial dimensions, or maybe even just one or two. Also, according to the theory of relativity, time is a dimension, so perhaps our universe could have been formed with two or more dimensions of time. Mind-boggling!
The fine-tuning argument for God
The fine-tuning argument for God is a type of teleological argument. In philosophy, teleology refers to an explanation of some phenomenon based on its purpose rather than its cause. It is also called an argument from design.
The fine-tuning argument is based on the fact that life as we know it is only possible because several of the fundamental constants have the values that they do. If any of those fundamental constants had even slightly different values, life as we know it could not exist.
The argument is that it is impossibly unlikely that all of those constants could have just the right values by pure chance. This suggests that the universe was designed to support life, which requires a designer. And we might say that a being who deliberately designed a universe to support life is, by definition, God.
Rejection of the fine-tuning argument
There are several arguments against the fine-tuning argument itself. Some people argue that the fundamental constants only describe the universe, rather than controlling it. Physicists have measured the constants, but they are what they are. There is nothing that indicates that they could be changed in any way.
Those arguing for the existence of God would make the case that, of course, an omnipotent God could choose the parameters of the universe however he wished, so that fundamental constants could have been different. But that is begging the question - they are assuming the existence of God to prove the existence of God, which is not a sound argument. If we start from the assumption that God does not exist until it is proven that he does, there is no good reason to assume that the fundamental constants can be changed at all.
And even if they could have been different, we have no way of knowing how unlikely the actual values of the fundamental constants are. Could the strength of gravity have been anything, from zero to almost infinite, all with equal probability? Or is the force of gravity constrained to a certain range? Or are certain values far more likely than others? Or could the universe have formed in a state where gravity didn't even exist at all? It is difficult to know whether our current universe was unlikely when we have no idea how the constants could have varied, if at all.
Notice that these arguments do not propose an alternative to fine-tuning (although there are some alternatives, which we will discuss later). Just because science doesn't provide an alternative answer doesn't prove that God exists.
It might be the case, from our place inside the universe, that it is impossible for us to ever find out why the universe is how it is. Although science has provided many unexpected answers in the past in fields such as cosmology, evolutionary biology, quantum mechanics, and relativity, so there is no telling what the future might hold.
A final observation some have made is that the universe isn't really that finely tuned for life. Within our solar system, only the planet Earth is capable of sustaining life as we know it. That is because of its exact distance from the Sun (providing temperatures that allow for liquid water), its magnetic field that protects us from solar radiation, the abundance of various elements on the surface, and the fact that these conditions have remained very stable for billions of years.
And even given that, only a fraction of the Earth's surface supports human life. We can't live in the sea, and we struggle to survive in polar regions or deserts.
We don't know how many planets like ours there are in other solar systems in our galaxy or other galaxies. There probably will be some, but perhaps not many. So if the universe was purposely designed for human life by an omnipotent God, it appears to be quite an inefficient design. The universe is unimaginably huge, and hardly any of it is compatible with human life.
Regardless of these rejections of the fine-tuning argument, the question of why the universe is as it is remains. Specifically, why does the universe support life when it seems like it could not have supported life at all?
Alternative explanations
While it is possible to reject the idea of God as an explanation for fine-tuning without necessarily providing an alternative explanation, many scientists have speculated on possible reasons for apparent fine-tuning.
The anthropic principle
The first common argument is the anthropic principle (more specifically, it is called the weak anthropic principle). It is simply this - it should be no surprise that we humans find ourselves in a universe that supports life. If the universe didn't support life, we wouldn't exist at all so there would be nobody to ask why the universe is like it is.
That argument is simple and obviously true, but it feels unsatisfactory. Here is an analogy. Suppose you were exploring in some remote and inhospitable jungle, and you fell while climbing a high cliff. You expected to die but instead landed on a large feather mattress, saving your life. You might ask why was the mattress here in the middle of the jungle, and how come it was in exactly the right place to break your fall.
Now someone could tell you that if the mattress hadn't been there you would have died so you wouldn't be able to ask any questions. That is quite true, but it wouldn't really be a satisfactory answer as to why the mattress was in that exact place, ready to catch you. The fact that you are alive at all is the very thing that demands an explanation!
A refinement of this argument is the strong anthropic principle. This says that the universe must support life, there is no possibility of a universe existing that doesn't support life. Remember that the weak principle only says that our universe happens to support life, but it doesn't necessarily have to. With the strong principle, there is no mystery as to why the universe supports life, it just has to.
Of course, we can't just state that the universe must support life and use that as our explanation. We need to justify it in some way. There are several, completely different reasons why people might think the universe must support life:
- People who believe in God, and believe that he created the universe for us humans, of course believe the universe must support life. God made it that way.
- Some scientists propose a different solution - the multiverse. They suggest that there are many different universes, maybe infinitely many, each with its own unique set of fundamental constants. Within all those many universes there will be at least one that supports life, and of course that is the one we find ourselves in.
- There is another strong anthropic theory amongst some physicists, that consciousness (rather than the physical world) is at the root of reality. The physical world arises out of consciousness, and as such would have to allow consciousness to manifest itself physically, in the form of life. This is quite a fringe theory, and it could be argued that consciousness here is just being used as another word for God. But still, as a scientific theory, its proponents know that they must develop experiments to prove it, rather than just asking people to take it on faith.
Life could take many forms
Another argument is that life may take many forms. Just because life as know it requires certain conditions doesn't mean that every possible form of life requires those conditions. It might be that life of some kind can appear wherever the conditions for evolution by natural selection exist. If evolution is possible, then given enough time life will evolve.
The basic precursor for evolution is the ability of a being to replicate itself, and for the new being to inherit the characteristics of its parent(s). The basic unit of life as we know it is the cell, and a cell contains DNA which contains information about how the cell will behave. The DNA is replicated when the cell divides.
Although cells are constructed of various chemical elements that are readily available on Earth, there is no reason in principle why a self-replicating system couldn't be constructed out of different chemicals, or even in a different way altogether. If the five requirements of evolution are present (Variation, Inheritance, Selection, Time, and Adaptation) then evolution can take place there is no reason to assume that life, consciousness and intelligence might not evolve.
There is another factor that the fine-tuning argument sometimes overlooks. Physicists can make educated guesses as to what might happen if some of the fundamental constants were slightly different. So they have mainly considered universes that are quite similar to our own. But, of course, universes that are similar to our own might only make up a tiny fractions of all the possible universes. What about a universe where all the parameters were wildly different? It is far more difficult to know what the result might be. And if we imagine that the universe might have had a different set of constants and different physical laws, then it is impossible to imagine what it would have been like. Who could anyone possibly imagine what it would be like to live in a universe with two separate dimensions of time?
So if we accept that the universe didn't have to be like it is, then we have to consider that it might have been very, very different. And, for all we know, out of all those possibilities, maybe a lot of them would have allowed for life of some kind.
Cosmomogical naturalism
Science primarily investigates the natural world, and time and time again things that were assumed to be supernatural have turned out to have natural explanations. The weather, outbreaks of diseases, natural disasters, and the movements of the Sun, Moon and stars, were all believed to be controlled by supernatural forces in ancient times, but now we know that they have natural explanations.
Fine-tuning is another unexplained phenomenon, and once again people look to God as an explanation. It is always tempting to do this when a natural explanation seems unlikely or impossible. But proponents of cosmological naturalism would point out that we have been in this situation many times before, and the answer, when it was finally found, is never God! They see no reason to believe that the universe is controlled by anything other than natural processes.
An alternative explanation for the apparent coincidences in values of the fundamental constants might be that they are constrained in ways that we do not yet understand and that perhaps there are fewer than 22 constants as they may be linked in ways that we do not yet understand.
Possible supernatural explanations
In common with many arguments that claim to prove the existence of God, the fine-tuning argument doesn't prove the existence of any specific God, such as the Christian God. It could be explained by any God, even one that hasn't revealed itself to us, or a deistic God (a God who created the universe but doesn't care too much about what we humans do with ourselves). Or any number of other natural or supernatural causes.
Summary
Fine-tuning is one of the most interesting arguments for the existence of God. We have all wondered why the world is like it is, but we can't even agree on the parameters of the question. Yet it remains a question that seems to demand an answer.