The Probability Argument for the Intelligent Design of the Universe

Continuing our discussion of the series of articles by Elie Feder and Aaron Zimmer on the various formulations of the argument for design of the universe based on cosmic fine-tuning, we turn today to the authors' summary of the formulation based on probabilities.

Feder and Zimmer use philosopher/physicist Robin Collins's version as representative of this approach. Collins's argument is succinct and relies on what he calls the Prime Principle of Confirmation which states that “whenever we are considering two competing hypotheses, an observation counts as evidence in favor of the hypothesis under which the observation has the highest probability (or is the least improbable).”

In other words, we should always favor the hypothesis which is most probable over competitors that are less probable. Thus, Feder and Zimmer write:

• Premise 1. The existence of the fine-tuning is not improbable under theism.
• Premise 2. The existence of the fine-tuning is very improbable under the atheistic single universe hypothesis.
• Conclusion: From premises (1) and (2) and the prime principle of confirmation, it follows that the fine-tuning data provides strong evidence in favor of the design hypothesis over the atheistic single-universe hypothesis.

His [Collins's] justification for premise 1 is that “since God is an all good being, and it is good for intelligent, conscious beings to exist, it is not surprising or improbable that God would create a world that could support intelligent life.”

His justification for premise 2 is the incredibly small likelihood of the constants having the proper values necessary by chance alone. Putting these together, he argues that fine-tuning strongly supports the hypothesis that an intelligent cause set the values of the constants.

Feder and Zimmer go on to mention a few difficulties:

Since we don’t know the probability distribution of each constant, it would seem that we can’t truly compute the relevant probabilities. This problem is addressed by Collins, Barnes, and multiverse scientists (who believe that the constants are set by chance).

They use plausible upper and lower bounds for the constants and then assume the probability distribution for the constants is linear. Though these seem to be reasonable assumptions, the objection still carries some weight.

The second problem they discuss seems to me to be less weighty:

A second problem with this formulation is, do we really know the probability that God would want to create a complex universe with intelligent, conscious, moral agents?

While this approach only needs the supposition that this probability is larger than the vanishingly small probability of fine-tuning assuming no intelligent cause, it could nevertheless be argued that God’s will is inscrutable and positing any knowledge about what God should do is engaging in a form of “divine psychology.”

Intelligent design theorists could obviate this difficulty, however, by restating the version of the argument given above this way:

• Premise 1. The existence of the fine-tuning is not improbable under the hypothesis that the universe is intentionally designed.
• Premise 2. The existence of the fine-tuning is very improbable under the naturalistic single universe hypothesis.
• Conclusion: From premises (1) and (2) and the prime principle of confirmation, it follows that the fine-tuning data provides strong evidence in favor of the hypothesis that the universe is intelligently designed.

By not specifying the designer the argument avoids the theological problems Feder and Zimmer cite. To get an idea of the staggering significance of a fine-tuned universe I suggest this post and this video:

Next time we'll look at the third version of the argument for design based on fine-tuning. It's the argument that Feder and Zimmer themselves favor.