Is the probability of getting a universe that supports complex life 100%?

Apologetics and the progress of science
Apologetics and the progress of science

Let’s have a quick review of the famous fine-tuning argument to start.

The argument from cosmic fine-tuning looks at various constants and quantities in our universe that are set at particular values and notes that if any of the values of these constants and quantities were to change, then complex embodied life of any kind could not exist. The argument is fully in line with the standard Big Bang cosmology, and is based on mainstream science.

There are two kinds of finely-tuned initial conditions: 1) constants and 2) quantities. These constants and quantities have to be set within a narrow range in order to permit intelligent life. There are three explanations for this observation: law, chance or design. Law is rejected because the numerical values of constants and quantities are set at the beginning of the universe – when there was no matter, space or time. The values of the constants and quantities were not determined by anything causally prior to the moment the universe began to exist. Chance is not a good explanation, because the probabilities are far, far too small for us to reasonably believe them (e.g. – the chance is 1 in X, where X is much higher than the number of subatomic particles in the visible universe). Since the fine-tuning is not due to law or chance, it must be due to design.

Here’s one example of something that is set correctly to allow complex, embodied life from The New Scientist:

The feebleness of gravity is something we should be grateful for. If it were a tiny bit stronger, none of us would be here to scoff at its puny nature.

The moment of the universe‘s birth created both matter and an expanding space-time in which this matter could exist. While gravity pulled the matter together, the expansion of space drew particles of matter apart – and the further apart they drifted, the weaker their mutual attraction became.

It turns out that the struggle between these two was balanced on a knife-edge. If the expansion of space had overwhelmed the pull of gravity in the newborn universe, stars, galaxies and humans would never have been able to form. If, on the other hand, gravity had been much stronger, stars and galaxies might have formed, but they would have quickly collapsed in on themselves and each other. What’s more, the gravitational distortion of space-time would have folded up the universe in a big crunch. Our cosmic history could have been over by now.

Only the middle ground, where the expansion and the gravitational strength balance to within 1 part in 1015 at 1 second after the big bang, allows life to form.

Changing the value at all means there would be no complex, embodied life of any kind anywhere in this universe.

Here’s a quick video clip to explain what The New Scientist is saying:

Now, this is going to surprise you, but there are some non-theists who try to argue that the finely-tuned constants and quantities that were set up at the beginning of the universe – long before we ever existed – are actually explained by our existence today. 

Atheist Jeffery Lowder summarizes a debate between William Lane Craig and Doug Jesseph, and Jesseph says something like this:

Craig’s argument is like asking the question, “What are your chances of landing in a universe hospitable to life, assuming you were tossed into any old universe whatever.” That is precisely not the point. It’s presupposed in the question that you’re already in a universe which favors life. Confuses conditional probability with unconditional probability.

Unlike me, Lowder is never snarky in his summaries, so this is guaranteed to be accurate.

Here’s what Dr. William Lane Craig says to that idea that our being here explains the fine-tuning:

Now some people have tried to avoid this conclusion by saying that we really shouldn’t be surprised at the enormous improbability of the fine-tuning of the universe because, after all, if the universe were not fine-tuned then we wouldn’t be here to be surprised about it. Given that we are here we should expect the universe to be fine-tuned. But I think the fallacy of this reasoning can be made clear simply by a parallel illustration. Imagine that you were traveling abroad in a third world country and you were arrested on trumped up drug charges, and you were dragged in front of a firing squad of 100 trained marksmen, all with rifles aimed at your heart to be executed. And you hear the command given – “Ready, aim, fire!” And you hear the deafening roar of the guns. And then you observe that you are still alive, that all of the 100 marksmen missed! Now, what would you conclude? Well, I guess I really shouldn’t be surprised that they all missed; after all, if they hadn’t all missed I wouldn’t be here to be surprised about it. Given that I am here, I should expect them all to miss. Of course not. You would immediately suspect that they all missed on purpose. That the whole thing was a set up engineered by some person for some reason. And in exactly the same way, given the incomprehensible improbability of the fine-tuning of the initial conditions for intelligent life, it is rational to believe that this is not the result of chance but of design.

Does it make sense? It’s true that any arrangement of bullet holes in a condemned spy is as unlikely as any other, but the vast majority of possible arrangements of 100 bullet holes result in you being dead. Being marksmen, the shooters definitely know how to hit a target at close range. It doesn’t matter if some hit your head and some hit your heart and some hit your throat – the most common consequence of a hundred bullets fired by expert marksmen at you is “dead you” – regardless of the specific arrangement of bullet holes. If you find yourself not dead, that requires an explanation. The explanation is design.

2 thoughts on “Is the probability of getting a universe that supports complex life 100%?”

  1. I’m glad to read Craig’s response since my doubt about the anthropic principle (as I was taught it) was that this is the only kind of universe that we could expect to appear in. Thank you sincerely for sharing.

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