Fine Tuning Argument

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This article is complex and parts are hard to understand. Sorry, I can't easily have only articles that are right for everybody. There are plenty of easier articles if you prefer them.


This universe is 99.99999 percent composed of lethal radiation-filled vacuum, and 99.99999 percent of all the material in the universe comprises stars and black holes on which nothing can ever live, and 99.99999 percent of all other material in the universe (all planets, moons, clouds, asteroids) is barren of life or even outright inhospitable to life. In other words, the universe we observe is extraordinarily inhospitable to life. Even what tiny inconsequential bits of it are at all hospitable are extremely inefficient at producing life—at all, but far more so intelligent life ….

One way or another, a universe perfectly designed for life would easily, readily, and abundantly produce and sustain life. Most of the contents of that universe would be conducive to life or benefit life. Yet that’s not what we see. Instead, almost the entire universe is lethal to life—in fact, if we put all the lethal vacuum of outer space swamped with deadly radiation into an area the size of a house, you would never find the comparably microscopic speck of area that sustains life (it would literally be smaller than a single proton). It’s exceedingly difficult to imagine a universe less conducive to life than that—indeed, that’s about as close to being completely incapable of producing life as any random universe can be expected to be, other than of course being completely incapable of producing life.

[And yet...]

That is exactly what we would have to see if life arose by accident. Because life can arise by accident only in a universe that large and old. The fact that we observe exactly what the theory of accidental origin requires and predicts is evidence that our theory is correct

The Fine-tuning argument attempts to claim that the physical, empirical scientific finding known as "Fine Tuning" indicates that there is a god. Fine-Tuning is, roughly, the observation that the laws of physics are such that changing the constants, even by a little bit, will result in a totally different universe, not fit for life. It is a Teleological Argument (specifically, it is a form of the Anthropic Argument), and is treated as such under that heading (go there!). The following deals with it more broadly.

The Fine-Tuning argument is held by many modern apologists, including Anthony Flew, William Lane Craig, Alvin Plantiga, George Schlesinger, Richard Swinburne, Robin Collins, Gerald Schroeder, and more. It is one of the most common argument raised in modern apologetics.

Note: These arguments even if they were reliable would at most prove an unspecified intelligent designer or an unspecified intelligent design team. This type of argument cannot prove any specific religion, denomination or sect, see How many gods?.

The Fine Tuning Argument

In the late 20th century scientists have realized a strange fact about the way the equations of physics are built - our emergent physics is extremely sensitive to changes in the constants of physics. If you change one of the constants even by a tiny bit, the world will look very very different - it will generally have no suns, no chemistry, and - therefore - no life. This is known as "fine tuning".[2]

The Fine Tuning Argument argues that fine tuning indicates that the universe is designed to support life. The idea is that all these other stars and so on are directed at supporting life, as they are what emerges from laws of nature that support life. Stars are needed to create heavy atoms, creating chemistry, and so on. The choice of constants is just what a designer would choose if he wanted to create life, so it is an indication of intelligent design in the construction of the universe.

Well, there are a lot of problems with this line of thought.

It Isn't an Argument

Perhaps the biggest problem of the FTA is that it isn't really an argument, it is a desired argument. The argument makes several hidden assumptions that are just not supported by science at the moment.

1) The argument presupposes that there is a certain range of possible values the constants can take. We don't know whether this is true, we have no idea what values the constants can take or if they can take other values at all. We don't even know what the possible constants are - maybe there are further constants with value zero in our universe?

2) The argument presupposes that there is no natural process of creating universes, or that if there is it isn't going to create a universe with our values of the constants. This is, again, just not something we know scientifically. There still isn't a well established scientific theory on how universes are naturally created, so we cannot say that it is unlikely for our universe to have been created naturally (indeed, many of the current hypotheses indicate that our universe was created naturally; but they are not yet proved). Nor are we in the situation where science has established that there is no natural way for a universe to be created. We just don't know enough about universes for this presupposition to be accepted.

In this respect, this is an Argument from ignorance or a God of the gaps argument. Saying that it is impossible for our universe to have been created naturally in this way is just like saying that the ordered shape of the hexagonal basalt columns of the Giant's Causeway could not have been created naturally. That is, of course, false. One can understand that the basalt columns are natural when one understand enough about how basalt is created and formed naturally. One cannot rule out a natural explanation until one has an understanding of the subject matter's natural behavior. Similarly, since we don't know how universes are created we just don't know enough to determine that the values of the constants in our universe are indicative of an unnatural process.

3) The argument is too quick to assert that other values will not result in life. We haven't explored all the various possibilities thoroughly enough to make such a pronouncement. We know slight variations will produce radically different physics, but we're far from knowing that no other constellation of constants will produce complex structures or how common or naturally likely to occur are such combinations. These are two separate issues that should not be confused. Indeed, it is possible that there are values that are more supportive of life, with life more pervasive throughout the spacetime of the universe.

4) The argument implicitly assumes that it is possible for a universe to be artificially created with a certain choice of values. While this might sound plausible, it is not necessary. Certain theories on universe-creation, for example, posit that the values are determined randomly due to symmetry breaking, so that there is no way for their creator or the process that creates them to determine these values in advance.

The argument implicitly uses these assumptions, and they are not established. Until they are established, it isn't even a (sound) argument.

It Doesn't Address the physical finding of Fine Tuning

The argument actually only uses the fact that these values are what a creator will choose if he wanted to create life, it doesn't use the fact that other choices will not result in life. But the actual finding is that small deviations will not support life, not that different values cannot support different types of life.

Note that the existence of other possibilities of creating life doesn't mean that life isn't designed - if there are multiple ways to create life, choosing one of them is just as indicative [or non-indicative] of design as choosing the single option if it is the only option. If there are two ways to design a flying buttress, the fact that the engineer chose one is still a result of intentional design. Thus, imagine that changing some constant slightly, to some other close value, will still result in life. The argument still works, since the fact that God chose one of these two close possibilities is still design. The argument doesn't utilize the actual finding of fine-tuning, which is that no such close sets exist.

Furthermore, the argument doesn't explain fine-tuning. It takes fine-tuning as a given, as something God chose to put into the universe, rather than explaining it. Again, the finding isn't that the constants are such that they support life, but rather than small deviations from their empirical values will not produce life. The argument doesn't explain why this should be so. This fact remains completely mysterious, and this is because it isn't at all used by the argument.

It is bad theology

The argument is usually advanced on behalf of an omnipotent god. But an omnipotent god is not limited to the specific list of constants, or indeed to any specific list. He could create life in any way he pleases, and indeed can create life in a universe that is otherwise controlled by laws of physics that do not support life. At least the way the argument is usually fielded, that pictures God as choosing the one option that creates life, belittles god. Instead, one should think of an omnipotent God as choosing one of the myriad ways to create life: the establishment of these specific constants as the constants of Nature, in these specific values. This is but one of the many ways God could create life, so that the actual empirical finding of fine tuning loses its relevance and the argument is reduced to "The universe works in a way that supports life, ergo God!".

Furthermore, the argument demonstrates that God is not omnipotent, or else fails completely. For if an omnipotent God wanted to create life, he could have surely chosen other constants or other values or constantly intervened so as to create more and better life. The vast bulk of our universe, and our Earth, does not support life. Hence, either God is weak and so could only choose to create life in this way, or else his choice to create life in this way is indicative of other desires that are achieved simultaneously in this way and are important enough to warrant limiting life to a tiny fraction of the universe. In the latter case fine-tuning is not a good design-choice to create life. Fine-tuning is therefore not indicative of intelligent design, unless the theist can come up with some other purpose and explicitly show how fine tuning serves it.

The argument leads to eternal regress

The argument opens itself up for eternal regress. If god designed the universe to support life, this means that god itself has features that lead to the creation of life. The same argument therefore applies to the higher level - it follows that God was created in order to create life. And this God-creator was itself designed to create life, and so on and so forth.

It isn't exactly true

The argument is based on the assertion that changing one constant would lead to a universe in which life could not exist. This may be true. But more recent examinations of the consequences of changing several constants simultaneously have suggest that various life-friendly universes could be generated. So ours isn't really that special after all.

It has failed when applied on a smaller scale

For most of humanity's history, there was only one place in the Universe that we had detailed knowledge of, and that was the Earth. One could reasonably argue that it was fine-tuned for us and our food sources. It is not too hot and not too cold, it is well-illuminated, it has plenty of water for us, and so forth.

But as we explored the Solar System, it became evident that most of it is hostile not only for us, but also for just about all of the Earth's biota. Only the Earth is not too hot or too cold, while being big enough to hold an atmosphere. So this seeming fine tuning is a result of planetary natural selection.

Is the Solar System anything unusual? The discovery of large numbers of exoplanets suggests otherwise, and discovery of them is mainly limited by our ability to detect evidence of them. That only adds to planetary natural selection and subtracts from planetary fine tuning.

One can argue similarly that the Sun is fine-tuned for us, being long-lived and reasonably stable. But natural selection operates here also.

The multi-planet natural-selection solution to the Earth's fine tuning can be extended to the Universe and its physical laws with the help of the Multiverse hypothesis. Our Universe would be one of many "Universe bubbles" in it, each with its own effective laws of physics. That would explain why our Universe is only borderline habitable; most other universes would not be habitable at all. Physicist Max Tegmark has classified various multiverse hypotheses in Parallel Universes.


  1. God Is Still a Delusion
  2. There is some doubt whether this is even true. See, for example, Anthony Aguirre, PRD 64, 083508 (2001). For the purposes of this discussion, however, let us accept it as a fact.

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