If we were to discover somehow that (sentient) life was so unlikely that it were almost impossible that it forms even once in the whole universe, does that imply anything about creation e.g.?

My logic would be that in the event that there was no sentient life, there would be nobody (as in the vast majority of other 'possible universes') to observe this fact. Therefore it doesn't matter how unlikely sentient life is because we are here now (and the likelihood of creation doesn't increase).

I'm not sure how to express this more formally. Is this sensible or flawed?

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    Have you read up on: en.m.wikipedia.org/wiki/Anthropic_principle ? Feb 28 at 4:18
  • 1
    Kind of seems an implausible possibility, considering that we are right here being alive and all that. Particularly in a universe so expansive that physicists literally consider the possibility that we might be boltzman brains.
    – Shayne
    Feb 29 at 9:20
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    If this is about statistics, isn't the operative term here 'Nearly'…? Either way, isn't the idea that it doesn't matter how unlikely sentient life is because we are here now basically a re-statement of the anthropic principle, which search? Feb 29 at 13:52
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    It's flawed. It's essentially begging the question in the naturalism vs theism debate. The longer the odds are for biogenesis the more it looks like a supernatural origin. 1 in 10. meaningless. 1 in 10,000. Might sway a few minds. 1 in 10,000,000,000. Might sway a lot of minds. 1 in 10^50. Now we've got real evidence for theism. 1 in 10^100. Why does anybody believe in naturalism anymore? 1 in 10^1000. Like the 1 in 10 but for the other side. (Note that these are whole universe odds numbers not one planet odds numbers.)
    – Joshua
    Feb 29 at 23:46
  • 2
    Winning the lottery is "statistically nearly impossible". But the probability of existence of a winner in each game is 100%. Probabilities are not facts.
    – RodolfoAP
    Feb 29 at 23:52

15 Answers 15


If, and it's a big if, it could be proved that the probability of the emergence of life through natural causes was exceedingly close to zero, then you could still assume life emerged by chance. Before adopting another explanation, you would still need to justify it. If there are two possible causes for an outcome, the fact that one is improbable does not automatically make the other probable.

  • 3
    For me, this is the most important aspect. We are not in a multiple choice test where one of the proposed answers is correct. Maybe we just don‘t have a good explanation for the emergence of life.
    – wra
    Feb 28 at 21:34
  • The problem here is that all of science, and naturalism in general, rely upon making predictions of statistical likelihood, and sorting what we consider likely from the multitudes of exceedingly improbable alternatives. YES -- this assumption of statistics being useful to figure out what is true is possibly wrong, but throwing it out -- does not PRESERVE either ontological or methodological naturalism. It is just a desperate recourse to maintain anti-theism, and is pretty clearly VERY motivated reasoning.
    – Dcleve
    Mar 1 at 15:42
  • @dcleve what????? Desperate recourse? Motivated reasoning? What are you on about? Mar 1 at 16:42
  • My answer consists of a valid if-then statement, a valid statement about good practice, and a true statement about probability theory. Which of the three do you deny? Mar 1 at 19:32
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    @MarcoOcram -- We are looking at three possible explanations: 1) something we know to be vanishingly improbable actually happened in this singular universe. 2) BECAUSE we dismiss something that is vanishingly unlikely under the "explanatory utility" of methodological naturalism, we postulate an infinity of other universes, so life is no longer vanishingly unlikely, with the downside of this being an untestable assumption. 3) We postulate agency from outside our universe, then investigate that to develop a suite of evaluable claims. That we cannot specify probability for 3 today is no problem.
    – Dcleve
    Mar 2 at 18:42

[This is a complete rewrite of my answer.]

If I understand you're question, you're presuming that we somehow determine that the chance of all the conditions necessary to result in intelligent life is so infinitessimal that, even given the vastness of space, they should never have occurred in the lifetime of the universe.

Yet somehow, we're here discussing this very situation -- something that never could have happened has actually happened. This seems like a paradox.

There are a few conclusions I can think of:

  1. There are supernatural forces that created us, e.g. there's an all-powerful god (or gods) that can act outside the parameters of the natural laws we've discovered, and which we used in making the above calculation.

  2. Our calculations were simply wrong, and the probability of intelligent life is more than we thought. So there's no actual paradox.

  3. Nearly impossible isn't completely impossible. Space is so big that something nearly impossible might happen once, maybe even a handful of times. But it may still be so rare that if we go looking for evidence of another occurrence, it will be practically impossible to find them. It would be like if 5 marbles were distributed at random places on Earth -- if you happened to find one of them, you'd still be hard pressed to find any of the others.

If I had to wager, I'd go with #2. Scientists have made mistakes like this many times in the past, because we often have incomplete information.

We're essentially talking about the Drake Equation. It includes a number of parameters that are estimates, and some are just educated guesses. As we've learned more about the universe and evolutionary priocesses we've been able to improve these values, but it's still imprecise.

The Copernican Principle says that there's nothing special about Earth, and by implication, humanity. So if intelligent life can arise here, it can in principle arise somewhere else that's compatible with higher orders of life.

Arthur Eddington once wrote:

If your theory is found to be against the second law of thermodynamics I can give you no hope; there is nothing for it but to collapse in deepest humiliation.

As an atheist, I believe we can say something similar about a theory that intelligent life can't possibly result from natural processes. If a theory claims this, I think it's more likely that the theory is wrong than that there's a god.

It's remotely possible that we atheists are wrong. But science has a very good track record. No amount of prayer by itself has yet succeeded in launching a rocket.

Conclusion #1 is essentially the "god of the gaps" argument. It presumes if science can't explain something, it's evidence of the existence of God. But science has been consistently explaining more and more -- just because we can't explain something now, it doesn't mean we won't be able to explain it in the future. Gaps are being filled in all the time, and there's no way to know which ones will come next. Some explanations might be really hard to discover (there are some physics experiments that can be imagined, but carrying them out would require more energy than we can feasibly generate), but that doesn't mean they're not knowable in principle.


It's perfect valid to say that something being near-impossible doesn't say much about other possibilities, unless you have some independent insight into how likely those possibilities are.

Of course, if something is really improbable under a particular view, that does at least encourage investigation into alternatives.

Warning: Maths (optional)

The mathematical formulation of this would use Bayes' theorem.

Let's say there are only 2 possibilities (which is already a problem): G - a particular god exists who would create life, and N - naturalism is true and abiogenesis would need to happen for life to form. And we can say L is the existence of life.

So your premise is that P(L|N) is low (the probability of life forming if naturalism is true is low).

If we continue along the questionable path of there only being 2 possibilities, and we assume life can only form through abiogenesis or via a particular god, then, by definition, P(N|L) + P(G|L) = 1 (the probability of naturalism being true given that life exists plus the probability of God existing given that life exists must equal to 1 if there's no other possibility given that life exists). This would be how you get to the probability of God existing based on what we have (P(G|L)).

What we want to know is P(N|L) (or P(G|L), which we get from the above), i.e. what's the probability that naturalism is true (or that God exists) given that life exists.

Bayes' theorem is P(N|L) = P(L|N).P(N)/P(L).

We know P(L) = P(L|N)P(N) + P(L|G)P(G), i.e. the probability of life existing under any view is the probability of life existing under naturalism, combined with the probability that naturalism is true, and we add the probability of life existing given God's existence, combined with the probability that God exists.

So P(N|L) = P(L|N).P(N)/(P(L|N)P(N) + P(L|G)P(G)).

We know that P(L|N) is small. Let's be generous and say that P(L|G) = 1, i.e. life is guaranteed to come about if God exists.

But then we get to our problem: P(N) and P(G) (which is 1 - P(N) if there are only those 2 possibilities). This is the point where we just throw everything out the window, because nothing so far tells us anything about how likely those things are. Either of those could be anywhere between 0 and 1 (as long as they add up to 1).

This might lead you to ask what is even the point of Bayes' theorem and how does it make sense that you need the probability of something in order to know the probability of that thing. Well, consider the example of a cancer test. We can independently determine how likely cancer is in general, and then we can determine the probability that a specific person has cancer based on the result of the test and Bayes' theorem.

Using probability to try to compare things for which we don't have probabilities is questionable.

Probability matters, but so does contrivance

Let's consider one of the most contrived explanations for life: Last Thursdayism. This is the idea that God created the universe last Thursday in its current state.

Under this hypothesis, the probability of the Earth existing in its current state is 1. If we just consider the probability of life under various explanations, this will beat or match practically every other explanation. But then the universe could also have been created last Wednesday, or last Friday, or 5 minutes ago, and it could've been created by any one of infinitely many conceivable deities. And all those would give roughly the same probability of life given that explanation.

This is why the probability of life under various possibilities means practically nothing without some independent insights into how likely those possibilities are.

To determine the "best" explanation for the evidence, we could consider the explanatory power of various explanations, and that may include how probable something under a particular possibility, but also includes how many facts it accounts for, how many assumptions it makes, how much predictive power it has, how much of what's contained in the explanation is supported by observations, whether it's falsifiable, etc.

  • P(L) = 1 = P(N|L) + P(G|L) - Can you please justify this equation? I'm not seeing how this is true.
    – Mark
    Feb 27 at 23:11
  • @Mark P(L) shouldn't have been there, but the remaining part follows by definition from assuming that those are the only 2 possibilities (edited answer).
    – NotThatGuy
    Feb 27 at 23:48
  • Note that "there are only 2 ways live could have come about" != (God Exists XOR Naturalism is True) .... It could be BOTH! :D
    – Brondahl
    Feb 28 at 10:16
  • I think that $P(L) = 1$ is incorrect in the context of the scenario you've set up. Notably, your scenario presumes a "many worlds" sort of situation, which is the only way to explain that $P(L|N) < 1$. Viz. if there is only one possible "world", and we are in it, then $P(L|N) = 1$ since the event $L$ is necessary. You can see this with $P(L or N) >= P(L)$, so $P(L or N) = 1$ and also $P(L and N) = P(L) + P(N) - P(L or N) = 1 + P(N) - 1 = P(N)$. This implies that $P(L|N) = P(L and N)/P(N) = 1$ as long as $P(N) > 0$.
    – Him
    Mar 1 at 17:01
  • What you mean to do, I think, is to set up the whole problem in a "many possible worlds" context, in which case the prior for $P(L)$ is ???
    – Him
    Mar 1 at 17:01

It is generally a bad idea to invoke an infinity of other universes to explain away an otherwise reasonable inference about OUR universe. It is far simpler, and much more testable/refutable, if one presumes it to be the only universe.

What you are doing, is taking advantage of Quine-Duhem, and the infinity of other possible theories that Q-D asserts, to try to avoid a conclusion you do not want to accept based on a most reasonable theory. This is motivated reasoning, not reasonable inference.

IF you want to follow motivated reasoning to avoid accepting that an exceedingly improbable event happened for no good reason, AND dismiss that it happened due to agent intervention, the alternative is to argue that the calculations that suggest abiogenesis was radically improbable are possibly off by many orders of magnitude. There ARE enough uncertainties in the postulated process for abiogenesis, and the conditions under which it could take place, that even if our best estimate today is that it was radically improbable to occur anywhere in our universe, that our confidence in the calculation is not currently high. And I believe both are the case -- that our best theories about abiogenesis would currently predict it should not have happened in our universe, AND that there is still a lot of uncertainty about those calculations.

However, an honest philosopher should admit that the current abiogenesis evidence points toward an outside intervention in our universe as credible. Even if you do not want to accept the conclusion, AND the evidence is currently mostly speculative best guess calculations.

As an aside, the best reference I have read on Abiogenesis is The Origins of Life, by Freeman Dyson. Dyson describes the three critical features of the first protocell:

  1. A working semipermeable membrane, that can ingest and excrete
  2. A dynamic equilibrium of metabolic proteins
  3. A replicator that generates the cell

All three of these have been a challenge to create in a pre-botic environment.

Dyson articulates the challenges that RNA-first hypotheses experience. He does not consider RNA first to be credible.

He considers membrane first to be the most likely. THEN, the minimal dynamic equilibrium of 350-500 enzymes somehow developed in a free environment, then got engulfed by a membrane. THEN RNA developed in a protected cellular environment, accidentally, and parasitized/took-over the proto-cell -- hence the multiple origins of life.

Dyson's own calculations suggest the development of a dynamic equilibrium of hundreds of protein enzymes is -- extremely unlikely. He also notes that when he looks at everything a protocell had to do, it seems to have about half the complexity as the largest multicellular animal. And it took evolution 4 billion years to grow that large multicellular animal from the first protocell. So abiogenesis has to accomplish a complexity growth equal to all of what evolution has accomplished, in about 1/20th the time. It is an interesting book, with an interesting thesis, and openly admits there is a major plausibility challenge for all abiogenesis theories.

  • Comments have been moved to chat; please do not continue the discussion here. Before posting a comment below this one, please review the purposes of comments. Comments that do not request clarification or suggest improvements usually belong as an answer, on Philosophy Meta, or in Philosophy Chat. Comments continuing discussion may be removed.
    – Geoffrey Thomas
    Mar 1 at 10:29
  • 1
    I would take the idea of an outside intervention more seriously if someone could offer a plausible explanation of how it worked. Are we saying that in the early days of the Earth some god visited at various stages and caused a critical mass of molecules to jump an evolutionary gap so that they formed into something more advanced? Why do you think that has a high probability? Mar 2 at 7:33
  • @MarcoOcram I will reply on the chat link.
    – Dcleve
    Mar 2 at 17:19

Short answer

According to Eugene Koonin, it would serve as an argument for believing in an infinite (or at least hugely vast) multiverse.

Longer answer

About Eugene Koonin

Eugene Koonin, Ph.D.
NIH Distinguished Investigator
Evolutionary Genomics Research Group

Dr. Koonin graduated from Moscow State University, Moscow, Russia and received his Ph.D. in Molecular Biology from the same University in 1983. He has been working in the fields of Computational Biology and Evolutionary Genomics since 1984. Dr. Koonin moved to the US in 1991, first, as a Visiting Scientist, and then, since 1996, as a Senior Investigator at the National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, MD. Dr. Koonin's group performs research in many areas of evolutionary genomics.


The paper

On May 31, 2007, Eugene Kooning published the paper The cosmological model of eternal inflation and the transition from chance to biological evolution in the history of life (https://link.springer.com/article/10.1186/1745-6150-2-15) in the journal Biology Direct.

The Background section of the paper says:

Recent developments in cosmology radically change the conception of the universe as well as the very notions of "probable" and "possible". The model of eternal inflation implies that all macroscopic histories permitted by laws of physics are repeated an infinite number of times in the infinite multiverse. In contrast to the traditional cosmological models of a single, finite universe, this worldview provides for the origin of an infinite number of complex systems by chance, even as the probability of complexity emerging in any given region of the multiverse is extremely low. This change in perspective has profound implications for the history of any phenomenon, and life on earth cannot be an exception.

Eugene also includes an appendix entitled Probabilities of the emergence, by chance, of different versions of the breakthrough system in an O-region: a toy calculation of the upper bounds. I will quote an excerpt, so please refer to the paper to read the full appendix:

A ribozyme replicase consisting of ~100 nucleotides is conceivable, so, in principle, spontaneous origin of such an entity in a finite universe consisting of a single O-region cannot be ruled out in this toy model (again, the rate of RNA synthesis considered here is a deliberate, gross over-estimate).

The requirements for the emergence of a primitive, coupled replication-translation system, which is considered a candidate for the breakthrough stage in this paper, are much greater. At a minimum, spontaneous formation of:

  • two rRNAs with a total size of at least 1000 nucleotides

  • ~10 primitive adaptors of ~30 nucleotides each, in total, ~300 nucleotides

  • at least one RNA encoding a replicase, ~500 nucleotides (low bound)is required. In the above notation, n = 1800, resulting in E <10-1018.

In other words, even in this toy model that assumes a deliberately inflated rate of RNA production, the probability that a coupled translation-replication emerges by chance in a single O-region is P < 10-1018. Obviously, this version of the breakthrough stage can be considered only in the context of a universe with an infinite (or, in the very least, extremely vast) number of O-regions.

In brief, Eugene appears to be saying that abiogenesis, even when conceding very generous assumptions, is virtually impossible from a probabilistic standpoint, unless we live in a multiverse with an infinite (or at least a hugely vast) amount of O-regions, which would render even the most improbable event as likely.

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    One of the best places to find criticism of that is probably within the reviews included on that page, they raise objections such as: Is it really true that traditional natural selection could not explain the emergence of the replication and translation systems? Why should we assume that the emergence of translation and replication had to be coupled in the first place? Is a transition from anthropic selection to Darwinian selection possible and likely? Is it possible to assume such a transition without taking the high risk to reintroduce teleology everywhere in the evolutionary field?
    – NotThatGuy
    Feb 27 at 21:56
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    In any case, to conclude that life started due to X (whether X is the multiverse or God or anything else) based on the improbability of life starting to due an alternative (abiogenesis occurring in one very specific way) is to fundamentally fail to understand Bayesian statistics (especially when that alternative is specifically crafted for improbability). The probability of life starting due to X depends on the probability of X in absolute terms, which might just be zero (or even less probable), in which case the improbable abiogenesis alternative wins. There may also be other alternatives.
    – NotThatGuy
    Feb 27 at 21:56
  • @NotThatGuy What are your thoughts on Koonin's reponses to those critiques? (They are also available on the page.)
    – Mark
    Feb 27 at 22:09
  • I'm not sold on his responses. I'm sure I looked into this paper in more detail in the past, and I'm not too inclined to dig too deep into that again, especially given that the most I can really do when it comes to the actual biology within evolution-related arguments is point out when people have failed to understand evolution on even the most basic level (which is usually more than enough for arguing against creationism, and while this paper isn't creationism and is more sophisticated, the reviewers suggest it did not consider evolutionary means that would make things a lot more probable).
    – NotThatGuy
    Feb 27 at 22:20
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    I don't know of such a paper. It's usually the people arguing against evolution and abiogenesis who try to estimate how likely it is, whereas people doing actual science concern themselves more with building on existing knowledge or making a concrete evidence-based case for alternative hypotheses for some given theory. This is not to say Koonin doesn't do "actual science" in his evolutionary genomics research, but I am saying the argument from improbability that this paper is based on is unscientific.
    – NotThatGuy
    Feb 27 at 23:13

I agree with you that there are two different questions about an event:

  • Question 1 (Yes-No?): Did the event happen or not?
  • Question 2 (How?): If the event happened, how did it happen?

Solving the first question in the positive does not necessarily imply the answer to the second question. In general, the second question has to be answered by different methods than the first question.


If we were to discover somehow that (sentient) life was so unlikely that it were almost impossible that it forms even once in the whole universe...

That doesn't seem like something that could possibly be discovered.

In science, we can test and reject hypothesis. We can uphold models that are useful and that we fail to reject. But a "discovery" on the impossibility of abiogenesis is asking for proving a negative. It would imply that we are 100% certain that all possible ways in which abiogenesis could form have been ruled out or ruled excessively unlikely. However, we can never know for sure that there are no other ways that have not been tested.

Therefore, whatever you conclude following your "if" is of limited value, because such a discovery cannot realistically happen.


I would say that even if we were able to calculate this probability with absolute certainty (let's assume we can), than it wouldn't necessarily imply creation. Assuming that the probability of abiogenesis is incredibly small, we have a couple options:

  1. Life was created by a creator, therefore either
    • 1a: this creator has always existed
    • 1b: this creator was created using abiogenesis
    • 1c: this creator was created by another creator
  2. There is another, yet unknown reason that life was created.

Using these assumptions, 1b is definitely not true. Prob(abiogenenis) is incredibly small, so Prob(our universe is created by creator|creator is created by abiogenesis) x Prob(creator is created by abiogenesis) is so much more smaller.

1c is also kind of problematic, since for this grandparent creator we face the same problem of explaining where it came from. For each level of creator we go deeper, this story just becomes more and more awkward and hard to believe.

1a could be argued to be true. Although personally, I think a creator that has always existed is kind of problematic as well. Especially since our current understanding of physics is that our universe has a starting point. So either this creator has existed since the big bang, or it was created somewhere in between, or this creator does not exist in our universe.

option 2 could also be true. There are many things in life whose answer is so hard that we could have never come up with the solution without further knowledge.

Personally, I think abiogenesis is so much easier to believe than any of these options above. Please give your thoughts in the comments.

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    I am trying to create the term "adeogenesis" for 1b/1c. Mar 29 at 2:43

It all depends on your theory of probability. If you are using probability as a frequentist, then you would appeal to the set of all known universes with life. In this case, there is exactly 1 known universe and it has sentient life. That's 100% likely based on frequency. Of course, 1 is a very poor sample size, drawing into question the conclusion's strength. Now, going forward, if we were to meaningfully come to know about additional physical universes, we could absolutely revise in the spirit of Bayes. Of course, just what it entails to come to such knowledge in an empirical sense is problematic.

BUT if you use the term probability in subjective sense, it just feels or seems likely, then you are simply appealing to probability of personal intuition. But how reliable are your intuitions? Are they formed based on your empirical experience of a single, known universe? Are they due to your confidence about your understanding of epistemic modality and statistical and probability theory? Did you watch a lot of science fiction as a kid? As such, it might be best to accept that your question is highly metaphysical speculative and therefore a questionable philosophical enterprise to be engaged in if you accept a fallibilist's claim that that there are strong limits to our acquisition of knowledge.


No it doesn’t imply creation for the simple fact that no matter how improbable life is “statistically”, it would not be deemed impossible through natural means. And even if it was deemed impossible through current known natural means, one would have to rule out life being possible through some other unknown natural mechanism. Saying that “god did it” doesn’t explain anything nor does it reduce the improbability.

Let’s assume that we live in a determined world and that life came about in a determined way. Then, either a) it was determined that a God would create life or b) it just so happened that natural laws exist and are determined to create life. In other words, something would have had to determine what God did even in a) just as much as b). But why prefer a) if b) is simpler?

Now, let’s assume that we don’t live in a determined world. Then, life came about atleast partially randomly. Then, either a) God created life (out of His free will which is supposedly random) or b) natural laws, in a somewhat random fashion (such as through quantum mechanics) resulted in life. Again, there is no reason to prefer a) over b). Both propose undetermined causes; however, a) is more complex. b) doesn’t have the extra ontology of an all knowing, all powerful god who supposedly exists outside of time and space in a bodiless form (whatever that means).

The only reason one would prefer a) over b) is if one has independent prior evidence of God. But we have no independent past experience of God existing, much less designing anything.

When we see someone draw a Royal flush five straight times in poker, we don’t assume that someone rigged the game just because five Royal flushes are improbable. After all, any sequence of cards drawn is just as improbable. We assume this because we have independent, prior experience and evidence of people existing and people being capable of cheating a poker game. We don’t have an analogous situation with God.


You noted that the existence of sentient life is a necessary condition for anyone to observe life, and that this might imply that no explanation is needed for such a vastly improbable event. This reasoning is flawed. Here's a scenario that explains why:

Imagine you live in a totalitarian country that kills of many of its people by means of a firing squad. You find yourself one of the 10 million sent to a firing squad and find yourself in front of 15 sharp shooters. From a distance of only 10 meters, they all shoot at you and miss. You think to yourself, "Hey, lot's of people get sent to the firing squad. Surviving is unlikely, but hey, I survived. Therefore, I shouldn't be surprised that I'm alive for otherwise, I wouldn't be able to make this observation. Hence, me surviving needs no other explanation."

The above reasoning is flawed. First, when you compare the number of "attempts" for someone to survive with the likelyhood of surviving, the event of surviving is still very unlikely. Indeed, suppose each "sharp shooter" misses 5% of the time, or 1/20. Then for all 15 shooters to miss you, then (assuming independence, which is a reasonable assumption if we assume the misses were not intentional), the likelyhood of them all missing you is (1/20)^(15), which is less than 1/10^(19). Given 10 million "attempts" at survival, there's still less than 10^(7)/ 10^(19) or 10^(-12) chance of anyone surviving. That's one in a trillion, even given the 10 million "attempts" at survival. Such an unlikely event does strongly suggest that some explanation is needed.

(Note: I read a form of the above hypothetical scenario in some book that I read over a decade ago.)

Here is a much simpler example showing if condition T is necessary for condition A to occur, that doesn't mean A is explained away by T. Indeed, let A be the event that you get a 100% on a calculus exam, and let T be the event that you take a calculus exam. Clearly T is necessary for A to occur and yet the mere occurrence of T (to take the exam) does not explain why A happened (i.e. that you got a 100% on it).

But the universe is so big and so old...

The rest of this answer is my response, as a mathematician, to the answer by Barmer (which currently is the top voted answer).

He claimed, "The universe is big, really big, and it contains an unimaginably large number of planets...

"...So even if something is almost impossible, there's a decent chance it has happened at least once, and possibly even multiple times."

This claim is not correct. This is because exponential functions grow extremely fast, and independent probabilities build exponentially.

According to this source, even simple cells have 42 million proteins in them. Suppose that the simplest imaginable cell needs only 100 proteins (whether different or whether some are allowed to be exact replicas is not super relevant to the calculation below).

Proteins are folded up chains of amino acids, of which there are 20. Many proteins are hundreds of amino acids long. So a chain of length only 150 amino acids has 20^(150) different possibilities.

Suppose that for each of our (assumed necessary) 100 proteins is at least 150 amino acids long and that for each of them, there are an enourmous 20^(120) different chains of amino acids that would work equally well to yield the needed function for that protein. That means a random 150 amino acid chain has chances of at most 20^(120)/20^(150) or 20^(-30) of happening by chance (in any one "attempt"). In one "throw of the dice" of making 100 proteins, the chances of all of them being functional is thus 20^(-30) raised to the 100, which is 20^(-3000). Actually, 20^(-3000) is off, due to being able to reorder 100 proteins in 100! (100 factorial) ways. Since, 100! < 20^(122), the probability bound in this example is 20^(-3000+122), or 20^(-2878).

The universe really is big. Indeed, some physicists estimate that there are 10^(80) atoms in the observable universe. Sure it's old: 13.7 billion years, which is less than 10^(30) picoseconds. If in each picosecond since the big bang, each and every atom of the universe "threw dice" to give an attempt for our 100 (assumed necessary) proteins, then that's only 10^(80+30) = 10^(110) attempts. If instead, each atom "attempted" to get all the proteins 10^(20) times each picosecond, then the number of attempts increases to 10^(130). Compare that number of attempts with the probability 20^(-2878). Sorry, but the size and age of the universe is no match for this probability.

The above scenario is only meant to show how easily one can arrive at a small probability for abiogenesis to occur without the input from a designer/creator. I have not proved that 100 proteins are necessary. I am just showing that it is extremely easy to calculate a probability for abiogenesis that far surpasses the number of attempts inside this one universe.

  • Thank you, neatly illustrated.
    – Spike0xff
    Feb 28 at 3:36
  • 1
    I read the firing squad analogy in one of William Lane Craig's books -- I think Reasonable Faith. It also appeared on his website.
    – Null
    Feb 28 at 6:55
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    @Jack Biologists have a number of hypotheses on the origin of life, but nothing substantiated. They try to appeal to natural selection before the first cell, but Theodosius Dobzhansky stated, "Pre-biological natural selection is a contradiction in terms." Feb 28 at 19:06
  • 1
    I said nothing of where amino acids come from, nor of their chirality, nor of cross reactions with unwanted molecules, nor of needed genetic information in DNA/RNA, and I assumed only 100 proteins instead of 42 million. Biologists and chemists have the burden of proof to demonstrate that the setup of only 100 proteins isn't already a gross oversimplification of how difficult the real problem is. Feb 28 at 19:07
  • 1
    Lies, Damned Lies, Statistics, and Probability of Abiogenesis Calculations: talkorigins.org/faqs/abioprob/abioprob.html Feb 29 at 9:38

It would change nothing whatsoever for me. "Nearly impossible" is an empty phrase. Either something is possible, or it is not possible. We know that it is possible (we have a positive test case of 1 in our own world), problem solved.

We know that this universe supports at least one intelligent species, and we know no reason whatsoever that it is impossible that a second species wouldn't then also evolve. To say it positively, although we were not around 4 billion years around when the first small signs of life appeared, we do have some pretty good theories how it could have happened, even only applying our current understanding of biochemistry (obviously we have the benefit of hindsight, but nevertheless). That means, we have not a single reason to believe that something like an extra-universal entity, or multiverses, or totally new swaths of physics or chemistry, or whatever you wish, was required for life to evolve on Earth. Being improbable has nothing to do with that. Many things are improbable and still eventually occur.

Note that the human brain is generally not good at interpreting probabilities, nor with interpreting infinity or impossibility, nor with understanding how infinity is different from "very very probable or improbable". These are different categories - infinity is not a number; and and a probability of exactly 0 or exactly 1 is qualitatively different from any other probability inbetween (i.e., for many questions we may have no clue how probable it is, but we may be able to say pretty deftly whether it is impossible, or possible, or utterly predetermined). Infinity is in the maths often just a shorthand for saying "no matter how large you make this number", and the universe has many numbers that are much larger than our brain can intuit about.


I won the main prize the very first time I bought an Art Union lottery ticket. I was about twenty at the time. After that, the chances of me being a lottery winner went to 100% and stayed there.

Someone wins the lottery every week. Abiogenesis is a bigger ask but you only have to get lucky once. Being a 1 in 10100000 year event doesn't mean it must happen at the mid-point of that interval, it can happen quite early in the story, like my win. Or not at all.

Me sitting here telling you about my art union is exactly parallel to the anthropic principle. The chance I will win a lottery is 100%. It was unlikely but now it's a dead cert. The chance abiogenesis will occur within the already elapsed life of the universe is 100%.

For that matter I watched someone roll 22 consecutive doubles in a game of Backgammon (we forgot about the rule limiting that). Amid cries of "this is bs!" from flatmates and classmates he just kept giggling at his opponent's dismay and rolling them out.

Extraordinary things happen non-stop.

  • This answer could be improved by explicitly adding your conclusions to explain how what you say bears on the question. (I have in mind the conclusion is that no special implications follow from the occurrence of an unlikely outcome.)
    – Ludwig V
    Mar 1 at 12:08

As long as our sample size is 1, it doesn't matter what we think the probability of us happening randomly is, as long as we also believe in an infinitely large universe. Even if it was extremely unlikely for life to spontaneously appear in the volume of our observable universe, that makes it far from unlikely to happen in an infinitely large volume of the whole universe. The only thing it would mean is that we should expect to be alone in the observable universe. It's basically the anthropic principle in action.

(Note I personally do believe in a creator, but as long as random chance is an acceptable explanation, you can never disprove it with a sample size of 1. Even then, when you find that life is more abundant than thought, you can simply declare your probability estimation was off.)


I would call your attention to the following two resources.

The first is to a public lecture by Professor David Kipping: "Why we might be alone".


The other is to a YouTube channel called "Closer to Truth". On this channel, Robert Lawrence Kuhn has interviewed many scholars dealing with your sort of question.

Channel: https://www.youtube.com/@CloserToTruthTV

Example video "Life in the Cosmos": https://www.youtube.com/watch?v=QFr10Z-pvOA

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    Feb 28 at 13:12
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