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Our Universe Survived a Firing Squad and It’s Just an Accident?

According to the Weak Anthropic Principle, if things weren’t the way they are, we wouldn’t be here and that’s all there is to it

Walter Bradley Center director Robert J. Marks has been doing a series of podcasts with Swedish mathematician Ola Hössjer, and Colombian biostatistician Daniel Díaz in connection with a recent co-authored paper on the fine-tuning of the universe for life in the Journal of Cosmology and Astroparticle Physics. In the first portion of this episode, podcast 153, “Why is there fine-tuning everywhere?” they looked at whether life was seeded in our universe by advanced life forms (directed panspermia), as advocated by some prominent scientists. In the second portion, they discussed the view — again, held by prominent science figures — that our universe is an advanced computer sim. Both concepts stem from the difficulty of accounting for the existence and complexity of life otherwise.

A third option is the Anthropic Principle. In its Weak form, it states simply that we are merely biased in thinking there is a reason we are here because, well, we are here:

This portion begins at 10:40 min. A partial transcript, Show Notes, and Additional Resources follow.

Robert J. Marks: Well, let’s move on to another theory. We’ve covered panspermia, sims theory. Another theory of the reason that we are here is the anthropic principle.

Ola Hössjer: The word, “anthropic,” means that the principle has to do with humans. It comes in two versions. The Weak and the Strong Anthropic Principle. The Strong Anthropic Principle was proposed by John D. Barrow and Frank Tipler in the late Eighties. And it holds that the universe is constructed for life to exist and for humans to live and thrive within the universe.

Note: British astrophysicist John D. Barrow (1952–2020) was known for his efforts to make science understandable to laypeople. “Barrow first won wide attention with his book The Anthropic Cosmological Principle (1986), cowritten with Frank J. Tipler. In this work the two scientists set forth weak, strong, and final versions of the anthropic principle—the notion that the universe contains conditions ideal for the development of living beings.” – Britannica

Frank Tipler is a mathematician and physicist at Tulane University. He specializes in General Relativity, as formulated in the Singularity Theorems of Stephen Hawking and Roger Penrose in the 1960s. Somewhat pugnacious regarding fine tuning, he takes the view, “If they (atheists) want a war, I intend to win it…”

Ola Hössjer: In that sense, the Strong Anthropic Principle is closely related to the view that our universe is fine-tuned for life to exist, and for humans to live within it. But it also adds an interpretation; it’s almost like a purpose. But the other version, the Weak Anthropic Principle, also deals with the fact that the universe is fine-tuned for life to exist.

But it says that, as humans, we are sort of biased, because we live in a universe that harbors life. It’s called selection bias. So it’s sort of a criticism of the strong anthropic principle, saying that, “Yes, if there was another universe without life, we would not be able to live in that universe and tell that it existed.”

According to the Weak Anthropic Principle, we should not be surprised to live in a universe that harbors life.

But I should add that, in our paper, “Cosmological Tuning Fine or Coarse?,” we compute or give an upper bound for the probability of a randomly generated universe to have a certain constant of nature, ending up within its life-permitting interval. We take the Weak Anthropic Principle into account — and still we come up with small probabilities for certain constant of natures or certain ratios or constants of nature.

So even though this Weak Anthropic Principle in a sense criticizes the Strong Anthropic Principle, we are able to come up with a small probability of ending up within the life-permitting interval and still not violating the Weak Anthropic Principle.

Robert J. Marks: One of the best counterexamples of the anthropic principle I heard is from William Lane Craig. I don’t think he was the originator of the idea, but it’s very clear from the work that we’ve been talking about, that the probability of our universe permitting life is very, very small.

Craig gives the example of a man dressed and ready for a firing squad. He goes out, his hands are bound and his eyes are covered, so he doesn’t have to look at the firing squad. In the firing squad, there are people who hate him. They are marksmen. There is one guy with a bazooka. A big explosion happens, and there is a lot of smoke. But when the smoke clears, the guy was still standing there.

His blindfold is gone; his hands aren’t tied behind his back. Everything was okay. He didn’t have a scratch on him. The (Weak) Anthropic Principle would correspond to the guy that was in front of the firing squad shrugging his shoulders and saying, “You know what? It happened. I don’t know why, but it did happen. I don’t have to worry about that, because I’m here. And that’s proof that it happened.”

Whereas, I think in reality, if we had a small probability event like this… If I was the guy in front of the firing squad, I might dedicate maybe a portion of my life to finding out why the heck I wasn’t shot. Why did this low-probability event happen?

I think the (Weak) Anthropic Principle is intellectually bankrupt.A number of physicists see this as an explanation that fits their ideology. But they’re really not wild about it at all.

Ola Hössjer: I totally agree with you. That example with the firing squad is a very nice one. I think if we apply the Weak Anthropic Principle to everyday life, we should not be surprised by anything.

Because we simply say, “Well, given that it’s happened, it sort of happened. And I cannot sort of say anything about the probability for it to happen or anything.” And I think that, as a philosophy of life, that is difficult to adhere to for anyone.

Robert J. Marks: Could we talk about the difference between the Weak and the Strong Anthropic Principles? We were talking about movies. There’s one of the first X-Men movies, where Dr. Xavier who heads the school for special mutants gives a homework assignment.

And he says, “Your homework assignment is to go home and write an essay about the Weak and Strong Anthropic Principle.” So the Weak and Strong Anthropic Principles have made it into the movies. What’s the differentiation between the two? What makes the Anthropic Principle weak? What makes it strong?

Ola Hössjer: If we start with the Strong Anthropic Principle, it’s really saying that it’s almost like the universe was constructed for a purpose for humans to exist and thrive within it because the probability for it happening by chance is so small.

And then, the Weak Anthropic Principle tries to weaken or explain away that first explanation by saying, “Yes. But given that we exist here, we cannot say anything about any other possibilities.” We are bound to simply accept that we live here. We are not going to think about the reason for this happening at all.

Popular culture tackles the question:

Daniel Díaz: Let me add one thing. And it is related also to your previous questions about how we measured the probability in our paper. Basically, the idea was taking the maximum of the probabilities over the restrictions we were considering. We are not considering only our universe but all the possible universes that could have existed under the restrictions that were assumed.

And then, once we are doing that, we remove the possibility of the Weak Anthropic Principle in our measurement. We are not just looking at our universe again. We are looking over all of the possibilities. And then, once we are doing that, we select the maximum. That’s why I mentioned before that we were conservative in our approach.

And then, in that way, we avoid the Weak Anthropic Principle.We don’t want to fall into the category of the selection bias measurement. Again, that is pretty common in scientific developments. The way to avoid it then was just to consider all the possibilities, and then take the maximum probability. That’s how we approach it in our paper.

Next: In an infinity of universes, countless ones are run by cats…

Here are all of the instalments, in order, of the discussion between Robert J. Marks, Ola Hössjer, and Daniel Díaz on the fine tuning of the universe for life:

The first episode:

Ours is a finely tuned — and No Free Lunch — universe. Mathematician Ola Hössjer and biostatistician Daniel Díaz explain to Walter Bradley Center director Robert J. Marks why nature works so seamlessly. A “life-permitting interval” makes it all possible — but is that really an accident?


Fine-tuning? How Bayesian statistics could help break a deadlock: Bayesian statistics are used, for example, in spam filter technology, identifying probable spam by examining vast masses of previous messages. The frequentist approach assesses the probability of future events but the Bayesian approach assesses the probability of events that have already occurred.

The second episode:

Life is so wonderfully finely tuned that it’s frightening. A mathematician who uses statistical methods to model the fine tuning of molecular machines and systems in cells reflects… Every single cell is like a city that cannot function without a complex network of services that must all work together to maintain life.

Can there be a general theory for fine-tuning? If you make a bowl of alphabet soup and the letters arrange themselves and say, good morning, that is specified. What are the probabilities? Ola Hössjer sees the beauty of mathematics in the fact that seemingly unrelated features in cosmology and biology can be modeled using similar concepts.

The third episode

Was the universe created for life forms to live in? How would we know? We can begin by looking at the fundamental constants that underlie the universe. The constants of the universe — gravitational constant, entropy, and cosmological constant — must be finely tuned for life to exist.

Why did Stephen Hawking give up on a Theory of Everything? Daniel Díaz and Ola Hössjer continue their discussion of the fine tuning of the universal constants of nature with Robert J. Marks. The probability, they calculate, that the fine tuning of our universe is simply random is down to 10 to the minus sixty — a very small number.

The fourth and final episode

Is life from outer space a viable science hypothesis? Currently, panspermia has been rated as “plausible but not convincing.” Marks, Hössjer, and Diaz discuss the issues. Famous atheist scientists have favored panspermia because there is no plausible purely natural explanation for life on Earth that would make it unnecessary.

Could advanced aliens have fine-tuned Earth for life? That’s a surprisingly popular thesis, considering how hard it is to account for life without assuming a creator. As Robert Marks, Ola Hössjer, and Daniel Díaz discuss, some prominent atheists/agnostics have chosen to substitute advanced extraterrestrials for God.

Our universe survived a firing squad and it’s just an accident? According to the Weak Anthropic Principle, if things weren’t the way they are, we wouldn’t be here and that’s all there is to it. Given the odds, a philosopher likens the Weak Anthropic Principle to surviving a firing squad and concluding, incuriously, well… that’s just the way things are.

In an infinity of universes, countless ones are run by cats… Daniel Díaz notes that most of the talk about the multiverse started to appear once it was realized that there was fine-tuning in nature. Robert J. Marks points out that even 10 to the 1000th power of universes would only permit 3,322 different paths. Infinity is required but unprovable.


If extraterrestrials didn’t fine tune Earth, maybe there is a God. In the face of a grab bag of ideas like creation by ETs or countless universes (some run by cats), why does the idea of a Creator seem far out? Traditional philosophers, not committed to a religion, have thought that deism (and theism) are rational, science-based conclusions, based on fine tuning.

You may also wish to read: No Free Lunches: Robert J. Marks: What the Big Bang teaches us about nothing. Bernoulli is right and Keynes is Wrong. Critics of Bernoulli don’t appreciate the definition of “knowing nothing.” The concept of “knowing nothing” can be tricky.

Show Notes

  • 00:33 | Introducing Dr. Daniel Díaz and Dr. Ola Hössjer
  • 01:53 | Panspermia
  • 04:59 | The Sims Theory
  • 10:40 | Anthropic Principle
  • 18:53 | Multiverse
  • 26:03 | The Creator Interpretation
  • 29:11 | Personal Beliefs
  • 36:24 | Final Words

Additional Resources

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Our Universe Survived a Firing Squad and It’s Just an Accident?