Fine-tuning and ordered creation

If you are an atheist or an agnostic, you may have met fine-tuning in a form that is easy to dismiss: Earth sits at exactly the right distance from the sun, so someone must have put it there. You are right to dismiss that. There are billions of planets at every distance from their stars, and we would expect to find ourselves on one of the habitable ones.

The serious version concerns something more basic: the constants and starting conditions of physics itself. Our best theories contain numbers that the theories do not explain, such as the strength of gravity, the masses of fundamental particles, the strength of the forces that hold atoms together, and the energy of empty space. They also require the universe to have begun in a very particular, highly ordered state.

The Stanford Encyclopedia of Philosophy explains the term this way: a model is fine-tuned “when it reproduces observed phenomena only if its parameters take values within an extremely narrow range among those that the theory in principle allows.” Change several of these values by small amounts and, on standard calculations, you do not get a different kind of life. You get a universe that expands too fast for anything to form, or collapses at once, or has no stable atoms and no chemistry, and so nothing that could become complex at all.

This is not a claim made only by religious writers. Physicists of every view discuss it. The cosmologist Martin Rees, who is not religious, wrote a book on six numbers that shape the universe and concluded that they needed explaining; he favors a multiverse. The question is what explains the tuning, not whether physicists notice it.

Some things are less settled than popular accounts suggest:

• Some physicists, such as Fred Adams, have argued that certain parameters are less finely tuned than often claimed; stars, for example, can form across a wider range of values than older estimates allowed.
• We do not know how to assign a probability to a constant of nature. Saying a value is “one in a trillion” assumes a way of spreading the possibilities that nobody has fully justified. The encyclopedia article discusses this as a real difficulty for the argument.
• We do not know what forms of life a very different universe might allow.

These cautions narrow the argument without removing it, because several of the parameters remain finely balanced on any accounting, and the starting order of the universe is among the most striking.

Fine-tuning is a fact that needs an explanation, and there are four main candidates:

• Luck. The values happen to permit life. That is a primitive fact and needs no further account.
• Necessity. A deeper theory, not yet found, will show the values could not have been otherwise.
• Many universes. Ours is one of a vast number with different values, and we find ourselves in one of the rare ones where observers can exist.
• Design. The values permit life because a mind with a purpose set them so.

Design is a hypothesis like the others and can be judged by the same test: how well does it predict what we see? If a purposeful Creator wanted a world with living, thinking creatures, a life-permitting universe is what you would expect. If the values were set by nothing at all, a life-permitting universe is a rare outcome among the possibilities. When one hypothesis predicts an observation much better than another, the observation is evidence for it.

Necessity remains a promise rather than a result. No current theory shows that the constants must take their life-friendly values. If one did, it would raise the next question: why do the laws of nature have a form that fixes them there?

The most common reply points to a selection effect: we could only ever observe a universe that permits life, since we could not exist in any other. That is true, and it explains why observers see fine-tuning. It does not explain why a life-permitting universe exists to be observed. The philosopher John Leslie compared it to a man who survives a firing squad of fifty marksmen when every shot misses. He is right that he could not observe his own death. He is still entitled to ask why every marksman missed.

The selection effect does real work when it is joined to a multiverse. If there are enough universes with varying values, some will permit life, and observers will be in those. Physicists take multiverse ideas seriously for independent reasons, arising from theories of the early universe, so this is not an invention to avoid God.

It has costs. A process that generates universes with varying constants must itself follow laws, and those laws need to be the right kind to produce any life-permitting universes at all, so the question of fine-tuning moves back a step. And the other universes cannot, as far as we know, be observed. That does not count against the idea, though it makes the multiverse a large theoretical commitment rather than a cheaper alternative to design.

At its best, fine-tuning is evidence that the order of the physical world reflects a purpose. It is not proof, and it does not tell you that the designer is the God of the Bible. It also does not answer the question of what explains the designer; that question is taken up in who created God?, and the related argument from contingency argues that the ultimate explanation must be something that exists by its own nature.

The conclusion also fits what Christians believed long before modern physics. The Psalms say that “the heavens declare the glory of God” (Psalm 19:1). Isaiah says God did not create the earth to be empty but formed it to be inhabited (Isaiah 45:18). Paul says that God’s power can be seen in what he has made (Romans 1:20). Christianity expects a world that is ordered, understandable, and fitted for life, and that is what physics has found.

If you weigh the evidence and conclude there is a mind behind the order of the world, that is not yet faith in Jesus, though it gives you reason to ask whether that mind has acted in history.