Fine Tuning, Anthropic Principle and Evolution

One popular reply to the fine tuning argument is to invoke the anthropic principle. However unlikely the conditions were that resulted in my existence doesn’t tell us anything about anything, because if I didn’t exist, I wouldn’t be here to complain about these conditions.

Shamik Dasgupta has an interesting argument against the anthropic principle being used in this way. He argues that this use of the anthropic principle can be applied to established scientific theories, such as evolution by natural selection, and can dismantle these theories.

Shamik concludes his essay with the following:

This last example reveals a deep irony in recent atheism. I am an atheist, so I would like to show that the fine-tuning argument is unsound. And I would like to do so on scientific grounds, by showing that there are scientific explanations of our existence. My guess is that Penrose (1989), Sober (2004), and Dawkins (2006) feel the same way. But if one appeals to the Anthropic Principle, as they do, one appeals to something that is contrary to the very scientific standards used to affirm the theory of evolution by natural selection—itself a central piece of the scientific explanation of our existence. Our defense of atheism must come from elsewhere.

The full essay can be found here:


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Haven’t read the Dasgupta paper here, but we have to differentiate between the Weak and Strong Anthropic Principles. The WAP just says that if there are regions in the universe which are life-permitting, then necessarily we should find ourselves in one of those regions. But that is just a tautology. It doesn’t answer the question of whether there should be any of those regions in the first place.

The SAP would go further and say that somehow the Universe (or multiverse) must have properties which will inevitably develop some life-permitting regions. If that is true, then that would answer the FT problem. But the question is why that should be true, given what we know and without theoretically invoking an multiverse for no other reason.

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Thanks for the helpful rely, Daniel. That’s a great way to express the distinction.

The first thing Dasgupta does in the article is define what he means by ‘anthropic principle’. He says it’s a version of the weak anthropic principle (WAP), and suggests there are many. I don’t know what other versions there are.

The way I read his article, he’s not saying that the WAP is false, but that the WAP can’t provide the kind of explanation that a scientific theory can. In particular, the WAP can’t be used to solve or dismiss the fine tuning problem.

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I have to agree that the anthropic principle doesn’t answer the question of why the laws and constants of physics are the way they are. I never saw it as a good response to the FT argument.


Is the Fine Tuning Problem a strictly scientific problem to begin with? If not, a scientific theory would not be expected to fully address it.

Obviously, the constants, and attempt to evaluate these in terms of fundamentals and probabilities, are scientific in nature, but the problem essentially boils down to “it seems odd that everything is so conveniently tuned for life”, which is as much a philosophical observation.

Or, from a perpendicular perspective, on what basis does the existence of life pose a scientific problem? Why does a universe with life demand a scientific theory, whereas a fog universe does not? Maybe the universe regards us as not the big deal we take ourselves to be.

I actually believe that fine tuning invites the notion of purpose to the universe, so I am not sidelining the fine tuning problem, but I do not see why a scientific theory would have to bear a full explanatory burden. So the Dasgupta paper is asking too much in addressing a problem that is not amenable in its entirety to the domain of science, and therefore the Anthropic Principle is a valid approach, in part exactly because it does not narrowly function as an absolutely scientific theory. This does not mean, however, that the Anthropic Principle is necessarily successful.

The anthropic principle (really, the weak anthropic principle) is one reason that I don’t take the fine tuning argument seriously. But I would not word WAP the way that you do. It is, after all, a principle rather than a theorem. It isn’t meant to give an explicit formula. It is more like the Douglas Adams puddle argument.

The last line of the cited paper:

Why does atheism require a defense? If a person chooses not to believe in gods, that’s a personal choice. Are people not allowed to have our own personal opinions?

I did read the cited paper. The claimed counter-examples are contrived and absurd. Which one of them would you like me to debunk?

By the way, I will be calling on Omphalism for the debunking. And once you realize that, you can probably guess how the argument goes.

What it amounts to, is that Dasgupta is making dubious assumptions about the past. His counter examples are in the form of a reductio ad absurdum. But the absurdity is not due to the WAP. Rather, the absurdity arises from his dubious assumptions.

I think you bring up a lot of interesting thoughts, especially here:

And here:

It seems like the properties of any universe would cry out for explanation, even if in some universes that cry will be forever unheard.

As for your mention of fine tuning, purpose and the anthropic principle, I think this may connect with what Dasgupta was trying to get at, but I’m not sure.

It’s best to read his paper yourself to really get his argument in detail. A short summary of his argument against a certain use of the WAP is as follows.

Let’s stipulate that the best mathematical models we have for our universe have free parameters, and that the range of those free parameters that result in a universe that includes living things like us is very small. I call this observation FT. The probability of FT given God seems to be close to 1. The probability of FT given not God seems to be very small. So FT seems to be evidence for God.

But wait, I point out that the probability of FT given my existence is equal to one, because if FT was not the case, then I wouldn’t exist. Now, the probability of FT given my existence and God is equal to the probability of FT given my existence and not God. So it turns out FT is not evidence for God after all.

This argument entails an unsettling consequence. Let’s say someone comes up with a theory that explains why the parameters take the value that they do. Call this theory UFT. The competing theory is that the parameters are unconstrained and randomly determined, call this RT. Well, the probability of FT given that I exist and UFT = the probability of FT given that I exist and RT, and so FT isn’t evidence of either the UFT or RT.

Shamik Dasgupta applies this argument to the theory of evolution, to dismantle most of the evidence for it. He uses this outcome as a reductio showing that the argument itself is flawed. The version of the WAP he defines can’t be used this way.

As an atheist, Dasgupta in closing seems to hold out hope that there will be a scientific explanation for fine tuning. I don’t think he considers this a purely scientific problem, or that he rules out that philosophy may be able to at least help in addressing the fine tuning problem. He really wants to show that the fine tuning argument for God is unsound. His conclusion is that the WAP cannot accomplish this. His “defense of atheism must come from elsewhere.”

Given this context (or better yet, the context of Dasgupta’s paper), how do you see your comments connect to his argument? It seems like they probably do, but I can’t see how, or whether you would agree or disagree with Dasgupta’s conclusion.

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There is a reason why the Fine Tuning argument is not asserted by raw diamonds dug from mines… and that is because raw diamonds are not able to reflect on their own existence.

The only time Fine Tuning becomes an issue is when human awareness reflects on its own existence.

Yes, this is tautological… but in a logically inescapable way!: wherever human life exists, there is self-examination.

Thank you for your reply; lots to chew on there - unfortunately, I’m on the road and booked out this week, so I might not be able to give it due consideration right away. I’ll be sure to lurk though, and catch up later!

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Which assumptions do you think are dubious?

More interesting, could you construct the same sort of argument, using Dasgupta’s assumptions, but without using the WAP as defined by Dasgupta: without using ‘I exist’ as one of the conditionals?

If so, this would be very interesting to me and potentially useful to Dasgupta.

I have corresponded with Shamik a couple times in the past, and I think he’d be interested in a counter-example. I don’t think this paper of his has been published yet, and if he’s still trying to publish this, it could be useful for him.

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He is assuming certain knowledge of the past.

I suggested omphalism, because that completely changes the assumptions about the past.

Take the example of your biological parents having to conceive you, or you wouldn’t exist. But maybe the world popped into existence yesterday, with your memories of your parents as part of what popped into existence. In that case, your parents did not conceive you and in fact you didn’t actually have any biological parents.

If you use a more traditional theory of the past (i.e. no omphalism), then everything that actually happened in the past has a probability of 1, and we can say that without needing the WAP. But, of course, even then you don’t really know what actually happened in the past. You only have your possibly mistaken beliefs about that. And you can still gather further evidence that could change those beliefs. The WAP does not argue against that.

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Thanks for the reply. Could you elaborate on what you mean by the following?

What do you mean by probability here?

We usually talk of the probability that an event will happen. For a past event that has already happened, the probability is obviously 1 that it happened, and WAP is not relevant to that.

Your question brings up another issue. For me, probability only makes sense when there is a suitable statistical model. And that’s why I don’t like the way you define “Anthropic principle”, because you reference probability without giving a suitable model. And those purported counter-examples use probabilities without providing a suitable model.

Wouldn’t that also apply to future events? For an event that will happen, the probability is one that it will happen?

The way I understand probabilities, in this paper and in my work, is more like the following. I look at a star with a telescope and watch how its brightness changes with time. I have some idea about the probability that that star has a planet around it before considering this data, and I can use that and the probability that I’d see this kind of change in brightness if there is a planet vs. a bunch of other possibilities, to figure out whether the data increases the probability that there’s a planet around that star. The probability in this sense is more about my degree of confidence.

Maybe Dasgupta isn’t committed to this understanding, and maybe he disagrees with it, but that’s the way lens through which I read his paper and consider his arguments. And in that lens, I can understand the idea of the probability of one explanation versus another, given a life-permitting universe. I think Hawthorne explains the fine tuning argument the way I understand it, with the same understanding of probability that I have, pretty well here.

If you think Dasgupta’s use of probabilities at the beginning doesn’t make sense, how do you think appealing to the WAP can refute the Fine Tuning argument for God?

If you don’t think it can, then it seems you agree with Dasgupta’s conclusion, although for different reasons. Maybe you have a different response to the Fine Tuning argument, one that doesn’t involve the WAP at all. In that case, the way you address the Fine Tuning argument “must come from elsewhere.”

Only in a fully deterministic world, where the future is completely determined. I don’t think that describes our world.

To be honest, I never really looked at that. The fine tuning argument seems absurd, so why bother to refute it?

If the world were different from what we see, we should expect there to be different scientific laws, rather than the same laws but with different constants. So the whole premise of the fine tuning argument seems misguided.

Is the entire cosmos fine tuned for our existence? I don’t think that is actually answerable. That’s part of why I’m an agnostic and not an atheist.

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Thanks for your thoughts, Neil.