(Redated post originally dated 22 January 2013)

I’ve blogged before about the fallacy of understated evidence. Here I want to explore further how it applies to fine-tuning arguments.

Let us define the “general fact of cosmic ‘fine-tuning'” as follows.

FT: some universe or other has the initial conditions, laws, and constants which make the existence of complex intelligent life of some sort possible.

Even if we assume that so-called cosmic “fine-tuning” is evidence favoring theism over naturalism, that argument commits the fallacy of understated evidence. In other words, even if the general fact of fine-tuning is more probable on the assumption that theism is true than on the assumption that naturalism is true, it ignores other, more specific facts about fine-tuning, facts that, given fine-tuning, are more likely on naturalism than on theism.

What are these other facts? Draper has identified three in his writings. (Click on the FT# for links to the supporting arguments.)

FT1: Our universe is not teeming with life, including life much more impressive than human life. (Given that intelligent life of some sort exists in some universe, the fact that our universe is not known to have relatively more impressive life is much more probable on single-universe naturalism than it is on theism.)

FT2: The only intelligent life we know of is human and it exists in this universe. (Given that intelligent life of some sort exists in some universe, the fact that the only intelligent life we know of is human and that it inhabits this universe is very many times more probable on single-universe naturalism than it is on theism.)

FT3: Intelligent life is the result of evolution. (Given that intelligent life of some sort exists in some universe,

the fact that it developed as a result of biological evolution is more probable on naturalism than on it is on theism.)

I think we can add a fourth fact to this list, one which is highly related to FT1.

FT4: So much of the universe is highly hostile to life. (Given that intelligent life of some sort exists in some universe, the fact that so much of our universe is highly hostile to life is more probable on naturalism than it is on theism.)

One objection to the claim that FT4 is more probable on naturalism than on theism might be this. If most of the universe were not hostile to life in the specific ways it is hostile to life–such as containing vast amounts of empty space, temperatures near absolute zero, cosmic radiation, and so forth–then there would be no life. This is because there would be no essential elements and no stars “small enough” to allow planets hospitable to life. (I have no idea if this objection is supported by physics, but let’s assume for the sake of argument it is.) Even if this were true, this doesn’t change the fact that God is, by definition, an omnipotent being who could have designed the universe in such a way that much more of it is conducive to life, not hostile to it.

The upshot is this. Even if the general fact of cosmic “fine-tuning” is more probable on the assumption

that theism is true than on the assumption that naturalism is true, there are other, more specific facts about cosmic “fine-tuning,” facts that, given cosmic “fine-tuning,” are more likely on naturalism than on theism. One of these more specific facts is that so much of our universe is hostile to life. Once all of the evidence about cosmic “fine-tuning” has been fully stated, however, it’s far from obvious that facts about cosmic “fine-tuning” favor theism over naturalism.

ETA: Revised entire post: added a definition of fine-tuning and the FT labeling scheme, clarifying FT1 and FT2, and clarified that FT4 is highly related to FT1.