The Argument

If the constants of the universe (mass, energy, gravity, electromagnetic force, etc.) were slightly different, nothing would exist. If the earth was a tiny bit closer or farther away from the sun, no life would exist on it. The world, and the universe as a whole, was extremely fine-tuned for life. Considering the infinite number of variables that would not have led to life, the amazing precision that it took to get everything just right for us couldn’t have come about by chance. The universe must have been deliberately fine-tuned for us, and the only thing capable of doing that is god.

How to debunk it

1. If precision is your parameter for establishing that something must have been purposely fine-tuned, then you’re only digging a deeper hole by proposing a universal fine-tuner. A fine-tuner must be even more finely tuned than the thing he supposedly fine-tuned. The very idea that caused you to conclude that the universe was fine-tuned to begin with (the overwhelming probability that things could, or would, have come out differently otherwise) must also apply to whatever you think did the fine-tuning. How, in light of the overwhelming probability that the thing in question (god) also could, or would, have been different, did he end up exactly the way he supposedly is—a perfect, universal fine-tuner? It’s an even bigger question than the one you’re claiming to answer. Because once you already have a perfect universal fine-tuner in place, for him to fine-tune the universe is not improbable at all. No, the question is how we got the perfect universal fine-tuner in the first place.
   Let me make it clear that this is a natural extension of the logic you yourself are advancing, not me. All I’m showing you is where it leads you if you apply it consistently rather than arbitrarily.
2. The idea that our current state of affairs is infinitely improbable, and therefore impossible without some guiding hand, relies on a misguided idea of retroactive probability. It’s a fallacious hindsight attempt to add up independent probabilities in order to show that our current state of affairs is infinitely improbable (practically impossible) and could therefore not have come about by chance. But that’s a reversal of causality and a misunderstanding of how probability works. You can’t just reverse causality by concluding that effects necessitate causes—that the causes exist for the effects.
   Causes bring about effects, not the other way around. And you can’t apply probability cumulatively and retroactively. It has to be applied independently and going forwards.
3. If the core logical problems with this argument are a bit difficult to handle, try to consider all the less desirable aspects of the universe that must, according to this argument, also have been fine-tuned. Consider how our sun is fine-tuned to give a considerable percentage of us cancer. Consider how it is fine-tuned to grow into a red giant in a few billion years and swallow the earth. Consider how fine-tuned our planet is for earthquakes, tsunamis, droughts and hurricanes. Consider how fine-tuned humanity is for war and genocide. How fine-tuned things are to cause nine million children to die every year before reaching the age of five. It’s the same exact line of reasoning, minus the favorable cherry-picking.

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