The Argument From Fine-Tuning

William Lane Craig often presents the fine-tuning argument: The values of the fundamental constants are fine-tuned, because if they would differ just by a tiny fraction, life would not exist.

The argument in detail:

  1. If the fundamental constants of the universe (e.g. the gravitational constant) would differ by just a tiny fraction, life would not be possible
  2. Life exists and therefore the constants all have special values
  3. Special values are unlikely
  4. Unlikely things are fine-tuned
  5. Fine-Tuned things can only be explained by a creator
  6. The universe as-is is unlikely (from 2 and 3)
  7. Therefore the universe is fine-tuned (from 4 and 6)
  8. Therefore the universe has a creator (from 5 and 7)

There are multiple counter arguments:

On (1):

  • Where does “tiny fraction” start? When would a fraction not be classified as “tiny”?
  • Every interval in the real numbers has uncountably infinite values, so the possible interval for life-containing universes has the same amount of possible values as any other interval (like -infinity..+infinity). So the classification of “tiny” does not really make sense.

On (3):

Given an uniform/even distribution of values for the constants (any real number has the same probability), it follows that every value is unlikely, whether a special value or a regular value. Even every finite interval is unlikely (improper prior).

On (4):

The event “1 million radioactive atoms in 1 m³ decay at the same time” is very unlikely. Does that mean that it is fine-tuned? Rolling a dice a thousand times with only sixes is unlikely. Does that mean it was fine-tuned?

On (5):

I do not accept that without further proof. Wouldn’t the fine-tuning argument apply to the creator too?

Here are more general arguments:

  • Why is it only allowed to vary the constants of physical formulas? Why not exponents? Why can’t one make up completely new formulas, particles, fields, …?
  • What about zero as a value for a constant? This can eliminate a physical force. This has a very interesting implication: If zero is allowed as a value for a constant, then there could be infinitely many other physical laws which constants just happen to be zero in our universe.
  • There is a hidden assumption in the proof: No other universes exists.