Fraser Cane, one of my favourite science news commentators on YouTube, recently made a video where he explained why he doesn't think the fine-tuning argument is a good argument (begining at the 4:13 point in the video). He gave a few of the standard responses, and I didn't think any of them were good responses, so I'm going to respond to them.
Most of the universe is uninhabitable
First, he said the universe is only barely habitable. The vast majority of the universe is uninhabitable. First, you have all the vast emptiness of space. Then you have stars that can't support life. Then most planets are also lifeless. Then, only the thin surface of some planets (like earth) are habitable.
This is not a good argument against the fine-tuning argument, and there are a few reasons. One reason is because it doesn't dispute the fact that if you changed any of the laws or constants by a hair, life wouldn't be possible at all. As I explained on on another post, the universe could be fine-tuned for the possibility of life even if there happened not to be any life at all. The existence of just one life form proves that the universe is habitable. If the constants of nature have to be fine-tuned before that could be possible, then the universe is fine-tuned for life even if life is extremely rare.
A second reason that I also mentioned on that post is that even given ideal conditions, the actual emergence of life might be an extremely improbable event. I discussed that in two posts recently where I tried to calculate the probability of getting a functional protein given the vast probablistic resources in the universe. My estimates and assumptions were rough, but based on them, it looks like we should expect the actual emergence of life to be rare. But the fact that it's even possible means the universe is fine-tuned.
A third problem with this argument is that empty space is necessary for habitability. Imagine if the entire universe were filled with a life-friendly atmosphere like here on earth. If that were the case, there would be two major problems. One problem is that there would be too much mass, causing the universe to collapse, ending any chance of life. The second problem is that there couldn't be any stable orbits. You need empty space so there isn't friction when planets orbit stars and stars orbit galaxies.
The universe would have to be habitable for us to be observing it.
The second point he makes is the anthropic principle. The universe would have to be habitable for us to be here observing it.
This is not a good response to fine-tuning either. If a thousand people aimed their rifles at me and fired, but they all missed, nobody would say, "There's nothing remarkable about the fact that you're alive since you'd have to be alive to consider whether there's anything remarkable going on." Of course it would be remarkable if I were alive! Me being alive would require an explanation because of how unlikely it would be for me to survive that many people shooting at me.
The anthropic principle is a version of the observer-selection effect. The observer selection effect would explain why we find ourselves in a habitable universe rather than an uninhabitable universe if we assumed both kinds existed (e.g. if we assumed a multiverse with random combinations of laws and constants). If there is a multiverse, and the vast majority of univereses were uninhabitable, the anthropic principle would explain why we find ourselves in one that's habitable. It's because a habitable universe is the only kind of univeres that can be observed. All observers observe habitable universes.
The anthropic principle only works as an explanation of fine-tuning if you combine it with a multiverse. But Fraser doesn't even suggest a multivere. If there are far more ways the universe could've been uninhabitable than there are for the universe to have been habitable, and there's just one universe, then the probability is that the one universe would be uninhabitable. The fact that we're alive at all shows that the universe is habitable. That requires an explanation just as being alive in the firing squan analogy requires an explanation. Why has the most unlikely thing happened? It won't do to dismiss the question on the basis that if it hadn't happened, we wouldn't be around to wonder about it.
I said more about this argument, including the puddle analogy that's often invoked, here.
Any universe is improbable.
A third thing he said was that if you threw a dart out of an airplane, no matter where the dart lands, it's improbable that it would've landed at that particular spot.
That's an argument I used to have as a college freshman against teleological arguments in general, but that's a terrible argument. As somebody who has a basic understanding of entropy and the second law of thermodynamics, Fraser ought to know better. While any random arrangement of parts in a closed system is equally improbable, there are certain kinds of arragements that are less probable than other kinds. Some are ordered kinds, and some are random kinds. To use an analogy, imagine dumping a box of alphabet cereal on the floor. Any random arrangement is equally improbable, but there are certain kinds of arragements (namely, the kind that spell words and sentences) that are far less probable than other kinds (namely, the kinds that don't spell words or sentences). In the same way, any random combination of values for the constants of nature might be equally improbable, but the combinations that result in habitable universes are extremely rare. That's the real issue.
We just don't know why the universe is habitable.
The fourth thing he said was that the fine-tuning argument shuts down scientific inquiry. If we don't know why the universe appears to be fine-tuned for life, we should say, "I don't know," and try to find out instead of suggesting God did it.
The problem with this argument is that it begs the question against a theistic explanation. It just assumes theism is the wrong answer. This is a response one could use against any hypothesis.
Consider the big bang as an explanation for the CMBR and the red shift of distant galaxies. One could just as easily invoke Fraser's argument and say, "I don't know why there's a CMBR or why there's a red shift to distant galaxies" instead of suggesting a big bang did it. You could run the same argument against cosmic inflation.
If Fraser doesn't think God is a good explanation, he needs to say specifically why. Is there a better explanation? Is God an insufficient explanation? Is there some reason to think God doesn't exist? Any of these could be a good reponse, but that's not where Fraser goes.
Imagine applying the same reasoning to an alleged crime scene. You look around and see what appears to be evidence that a murder took place, but your supervisor says, "Hey, if you don't know how the person died, then don't just assume a murderer did it. You should suspend judgment until you find out what did cause the death." Well, if everything at the crime scene points to a murderer, then that's what you should think is the explanation.
If you have good reason to think you've identified the correct explanation for some observation, then you're perfectly within your rights in concluding that your explanation is correct. There's no reason to say, "I don't know," and wait for the alledged right explanation as if you don't already have the right explanation.
Coming to a conclusion about the correct explanation for your observations doesn't mean you shut down inquiry. You can hold your belief provisionally and be open to changing your view if new information comes along. But you don't need to suspend judgment when you have evidence that points to a particular explanation.
Notice that nobody ever says the same sort of thing about any other explanation besides God. When they came up with the dark matter as an explanation for flat galaxy rotation curves, nobody said, "Don't use dark matter to explain galaxy rotation because that shuts down scientific inquiry. Instead, hold out for a better explanation." Dark matter didn't put an end to inquiry. People still proposed other explanations, like Modified Newtonian Dynamics (MOND). Whether you think the correct explanation for flat galaxy rotation curves is MOND or dark matter, you are free to be open to new information that might point to a different explanation. Having an exlanation doesn't shut down further inquiry.
Science is provisional. So is every field of inquiry. We make our best conclusions based on the evidence that's available to us. We don't withhold judgment about every single conclusion we come to merely on the basis that it's possible some new piece of information will come along in the future that overturns what we previously thought we knew. We don't stop investigating the world or testing what we think we know just because we think we already have the right answers. So there's no reason in the world to think that belief in God as the explanation for fine-tuning will put a stop to scientific inquiry.
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