Why does the universe appear so precisely calibrated for life? Is cosmic fine-tuning evidence for God, or could future physics make the mystery disappear?
In this episode of Unbelievable?, philosopher Alex Malpass and Oxford researcher Miles Donohue go head-to-head over one of the most discussed arguments for God’s existence: the fine-tuning of the universe.
The basic claim sounds startling. Certain features of physics appear to sit within an extraordinarily narrow range compatible with complex life. Donohue points to the cosmological constant as one example, describing it as fine-tuned to “1 part in 10 to the 90”.
For him, though, the argument is not supposed to be a knock-down proof.
“I’m not saying it’s a definitive debunking of atheism.”
Instead, Donohue argues that fine-tuning should be treated as evidence. If naturalism is true, he says, there seems to be no particular reason why the fundamental constants should fall within a life-permitting range. But if God exists, a universe capable of producing conscious beings and relationships may be less surprising.
As Donohue puts it:
“If a perfectly good, all-knowing, all-powerful God exists, then it’s not at all unlikely that God would fine-tune the universe for life.”
Malpass agrees that the apparent fine-tuning is interesting. His challenge is whether we are entitled to move from fine-tuned physics to a fine-tuned universe.
Could today’s fine-tuning simply expose the limitations of our current scientific theories?
Malpass suggests that what looks finely adjusted may turn out to be “a sign that the theory is not correct”. A deeper theory of physics could, in principle, explain why the constants have the values they do without invoking design.
That raises a crucial question: are we seeing evidence for God, or merely evidence that physics is unfinished?
Malpass compares the issue to earlier debates over biological design. Before Darwin, the complexity of the eye seemed to cry out for explanation. Evolution later provided what he calls a kind of “deeper biology”.
He asks whether the same could happen in physics.
“It just seems, like, imprudent, if nothing else, to anticipate that there might be some deeper physics about to come along which makes some of this go away.”
The debate then turns to what Malpass calls his “stalking horse” objection.
His concern is that defenders of fine-tuning sometimes compare a highly specific version of theism, such as an all-powerful, all-knowing and perfectly good God, with a very bare version of naturalism.
Malpass argues that this risks comparing unlike hypotheses. If naturalism were expanded with a deeper physical mechanism that tended towards life-permitting universes, would the apparent advantage of theism shrink?
Donohue thinks not.
He argues that such “enriched naturalism” risks becoming too specifically tailored to the evidence. By contrast, he says the traditional divine attributes are not arbitrary additions invented to explain fine-tuning.
Later in the conversation, Donohue offers a deliberately more modest assessment of the argument. Rather than claiming overwhelming odds such as 10 to the 90 to one, he suggests the evidential force might be closer to “10,000 to one”.
That shift produces one of the most revealing moments in the exchange.
Malpass responds that bringing the numbers down dramatically makes the disagreement much more philosophically interesting, because reasonable people can now weigh fine-tuning alongside other evidence, including suffering, divine hiddenness and the complexity of Christian belief.
Donohue agrees on one important point:
“I would never wanna say that atheists are irrational or unreasonable.”
The episode finishes with an even stranger argument: Malpass’ new “existential lottery”.
Given the astonishing chain of events required for any particular person to exist, could our own existence actually count against certain versions of theism rather than for them?
It leads the discussion into souls, personal identity, multiverses and infinity, and leaves both philosophers with more to argue about.
So does fine-tuning point to God?
Donohue thinks it provides serious evidence for theism. Malpass thinks deeper physics and alternative natural explanations remain very much in play.
Watch the full debate and decide which explanation you find more convincing.
