Intelligent Design Arguments and Cumulative Cases

As we saw in my reply to Wintery Knight, he (like many other proponents of intelligent design or ID) propose that there are multiple, independent lines of evidence which favor intelligent design over its alternatives. Here is a partial summary of the evidence ID proponents offer.

  1. “Cosmic Fine-Tuning,” i.e., the initial conditions of the universe and the values of the constants of the fundamental laws
  2. “Biological Fine-Tuning,” i.e., the biological information in the first replicator (origin of life). This is Meyer’s argument in Signature in the Cell.
  3. “Zoological (?) Fine-Tuning,” i.e., the the sudden appearance during the Cambrian period of many new and anatomically sophisticated creatures in the sedimentary layers of the geologic column without any evidence of simpler ancestral forms in the earlier layers below. This is Meyer’s argument in Darwin’s Doubt.
  4. “Biochemical Fine-Tuning,” i.e., the presence of irreducibly complex biological structures such as the bacterial flagella. This is Behe’s argument in Darwin’s Black Box.
How Correct Cumulative Cases Work
To make things simple, let’s pretend there are two facts, F1 and F2, and we want to argue that F1 & F2 combine into a cumulative case for one  theory (H1) over another (H2). How to do? Let’s do this in plain English, taking it one step at a time. The first step should be obvious.
(1) Fact F1 favors theory H1 over H2.
The next step is where I’ve seen a lot of people make mistakes. They will argue:
(2) Fact F2 favors H1 over H2.
The problem is that this approach doesn’t connect or link F1 and F2 in the needed way for a cumulative case. Instead, they should argue:
(2′) Given that fact F1 is true, fact F2 favors H1 over H2.
If both (1) and (2′) are true, then F1 combines with F2 to make a cumulative case for H1 and against H2.
What’s the Problem for Multiple Intelligent Design Arguments?
At this point, someone may wonder, “What’s the big deal? Why can’t intelligent design arguments be combined to follow this pattern?” The problem is that the cosmic fine-tuning argument seems to be at odds with the other arguments, and vice versa.
Let’s assume, but only for the sake of argument, that cosmic fine-tuning evidence is evidence favoring theism over naturalism:
(1) Cosmic fine-tuning favors theism over naturalism.
But observe what happens when we follow the pattern above:
(2) Given that the universe is cosmically fine-tuned for life, the fact of zoological (?) fine-tuning during the Cambrian period is evidence favoring theism over naturalism.
The first half of of this sentence is in tension with the second half. if  Cambrian animal forms are very improbable given the initial conditions of the universe, then that would be evidence against intelligent design in cosmic fine-tuning. If, despite the life-permitting initial conditions of the universe and the values of the constants of the fundamental laws, there is virtually zero probability that life would arise from non-life, new and anatomically sophisticated animals would arise from simpler animals during the Cambrian, or irreducibly complex biological structures would evolve, then that decreases the probability that an intelligent designer fine-tuned the initial conditions of the universe.

Indeed, the laws of the universe are so finely tuned, god “only” has to completely suspend them once or twice every hundred million years, when he suddenly learns that the laws of the universe are tuned so as to make crucial components of biological evolution physically impossible.

It is a clear prediction of the theistic hypothesis that a miracle working god would want to set up a world where he wouldn’t have to constantly perform miracles in order for life as we know it to exist, except for all the times he has to perform miracles for life as we know it to exist.

For more on this problem, see Trenty Dougherty’s and Ted Poston’s, “A User’s Guide to Design Arguments.”