I was having a discussion last night about my atheism, and it was suggested to me that agnostism is the only reasonable conclusion, as it leaves the door open for new information.

This made me think, were they right? Or is a total lack of evidence for a contrary position justification for a logical conclusion?

  • It is reasonable when absence of evidence is evidence of absence. That is when the existence of something should necessarily produce some evidence/results. Then lack of those results is a valid inference of non-existence
    – Nikos M.
    Commented Sep 19, 2022 at 16:11
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    "As a philosopher, if I were speaking to a purely philosophic audience I should say that I ought to describe myself as an Agnostic, because I do not think that there is a conclusive argument by which one can prove that there is not a God. On the other hand, if I am to convey the right impression to the ordinary man in the street I think that I ought to say that I am an Atheist, because, when I say that I cannot prove that there is not a God, I ought to add equally that I cannot prove that there are not the Homeric gods" -Bertrand Russell. It can mean thinkin god/s irrelevant as well as unreal
    – CriglCragl
    Commented Sep 19, 2022 at 23:19
  • Ten year old question comes to the top of my feed because the question was modified today. Bad form.
    – BillOnne
    Commented Sep 20, 2022 at 3:29

12 Answers 12


The dichotomy you state between agnosticism and atheism is false. This is perhaps one of the most misunderstood terms of the 21st century. You can be an agnostic atheist and an agnostic theist. In general, the split between agnostic vs. gnostic theists is more in the middle (closer to 50/50), whereas most atheists are agnostic atheists (there's just no way to prove for certain that God (or anything) definitely doesn't exist).

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    Couldn't it work like this: Gnostic Theist - Agnostic Theist - pure Agnostic - Agnostic Atheist - Gnostic Atheist; that is there is one scale of confidence in theism, from large positive confidence theism to large negative confidence in theism (=large confidence in atheism) and 0 in the middle for no confidence in either direction for plain old agnosticism.
    – Mitch
    Commented Dec 30, 2011 at 19:39
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    In practice, no one has exactly 0 views one way or the other (God or no God), and their reasons are never exactly equally convincing in both directions. People believe in God, or they don't, and even if they are aren't certain they tend to lean one way or another. Someone who doesn't want to for various reasons pick a side (maybe they're afraid of being shunned by their family & friends, maybe they just don't really care, whatever) are probably better referred to as noncommittal agnostics. To me that just says they haven't really thought about it or aren't in a position to make a decision.
    – stoicfury
    Commented Jan 1, 2012 at 22:25
  • This is an incorrect depiction of gnosticism. Concluding that a God exists, or that one does not, is not a "gnostic" process, which is one of direct certain knowledge. It is instead an inferential process about a contingent question. Like all such evaluations, is is not subject to two dichotomies, but to a four state logic: probably true, probably false, currently undetermined, and poorly articulated/nonsense claim. The last is agnosticim. The third is ignorance/uncertainty.
    – Dcleve
    Commented Sep 19, 2022 at 22:26

The lack of evidence for a contrary position is only justification for a conclusion if there is a good reason to expect that there would be evidence if the position were true. For example, there may not be any specific evidence that bigfoot does not exist. But one can make a case that if there were such creatures, someone would have found them by now.

I have a friend who likes to watch Ghost Hunters. My joke to her whenever she mentions an episode of the show is, "Isn't that the episode where they finally find proof of the existence of the paranormal?"

Agnosticism actually is the position that closes the door to new information. A theist may be open to disbelief if he is exposed to contrary evidence. An atheist may be open to belief if he sees evidence of god. Agnosticism is the position that no sufficient evidence of either god's existence or his non-existence is possible. That is, agnostics hold that the truth of god's existence or nonexistence is unknowable to humans. Agnosticism is the position that one cannot ever know that god exists nor can one ever know that god does not exist.

I think you're confusing agnosticism with weak (or critical) atheism. Weak atheism is a refusal to believe in a god due to a lack of evidence without claiming that one knows that no god exists. Atheism and theism are the two alternate positions on belief in god -- one can believe or one can not believe. Agnosticism is a position on the knowability of god's existence. (There are people who claim to hold positions that are neither theistic nor atheistic, but that's a different kettle of fish.)

[A]gnosticism is the view that human reason is incapable of providing sufficient rational grounds to justify either the belief that God exists or the belief that God does not exist. In so far as one holds that our beliefs are rational only if they are sufficiently supported by human reason, the person who accepts the philosophical position of agnosticism will hold that neither the belief that God exists nor the belief that God does not exist is rational. -- Routledge encyclopedia of philosophy

Lastly, I feel the need to point out that we routinely consider a claim disproven if it being true would require a violation of our understand of cause and effect. If I flip a coin and see that it came up heads, I conisder the claim that it came up tails to be disproven.

Why? Because the only way it could have come up tails and me see that it came up heads is some violation of my understanding of cause and effect. Could a supernatural being be tricking my eyes into seeing the coin come up the other way?

For any claim you accept as true, one can imagine some supernatural way it could be false. If we had to consider the supernatural as unproven or unknowable, we could literally not accept any claim as true.

  • Often, a difference is made between strong and weak agnosticism, where strong agnosticism is what you describe in your answer. What you call weak atheism is often called weak agnostic atheism, i.e. not believing in god, because one doesn't have evidence for his existence, but not denying the possibility of someone knowing about his existence. So, being agnostic is often seen as orthogonal to being theistic or atheistic, e.g. one could believe in god, and still think that he can't find evidence for his existence. When I meet someone who calls himself agnostic, I usually ask what is meant.
    – danlei
    Commented Dec 24, 2011 at 21:02
  • @daniel What you call "weak agnostic atheism" is weakly atheistic, since it includes a lack of belief in god's existence without a belief that god does not exist. But it is gnostic, not agnostic, since it includes the belief that it may be possible for man to know that god exists. Commented Dec 24, 2011 at 21:14
  • David, I don't have the time to quote proper sources ATM, so I'll quote the german wikipedia here (my shortened, rough translation): "The opinion, that god's [...] existence can't be known is called strong agnosticism. The position, that the existence of higher beings is not in principle incognizable [...], is called weak agnosticism. So, a strong agnostic would say 'I can't know, and noone ever will', while a weak agnostic would say 'I don't know'.". In general, I'd be very careful with those terms, as they're not used univocally. I'm quite sure you could find contradicting sources.
    – danlei
    Commented Dec 24, 2011 at 21:31
  • I would say that the position that the existence of higher beings can be known is the opposite of agnosticism, not a form of it. "[A]gnosticism is the view that human reason is incapable of providing sufficient rational grounds to justify either the belief that God exists or the belief that God does not exist. In so far as one holds that our beliefs are rational only if they are sufficiently supported by human reason, the person who accepts the philosophical position of agnosticism will hold that neither the belief that God exists nor the belief that God does not exist is rational." Commented Dec 24, 2011 at 21:37
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    And exactly that was my point: It's better to always ask what is meant when someone uses the terms (weak or strong) gnostic, agnostic, etc., because almost everytime I hear them, they're used differently. Some terms in philosophical discussions evolved over thousands of years and were used differently in different philosophical systems, in short, they are highly equivocal. Add to this that many peoply are not aware of different definitions and usages, and you'll understand why I arived at my "always ask" position.
    – danlei
    Commented Dec 24, 2011 at 21:38

Is it reasonable to arrive at a conclusion based on lack of evidence to the contrary?

Of course it is; we do it all the time. Most of us have concluded that the moon is not made of green cheese because there is no evidence to the contrary.

We have a near-infinite number of hypotheses that face us daily, and we make judgments based upon the evidence, for and against, we have available. None of this adds up to certainty (in a philosophical sense), but from a pragmatic standpoint we usually have all of the certainty we need.

  • do you have any good examples?
    – Mild Fuzz
    Commented Dec 24, 2011 at 19:51
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    Odd. I concluded that the moon is not made of green cheese because there is copious evidence to support contrary positions, including rocks from the moon.
    – philosodad
    Commented Sep 19, 2022 at 22:15
  • @philosodad -- Good point. Also -- green cheese in our experience requires first milk, then a human treatment process for the milk, then a colony of mold to inhabit the cheese. With no milk producers in orbit, no humans doing the cheese making, and no mold -- there are very good reasons to think the moon could NOT be made of green cheese, even before we had any moon rocks.
    – Dcleve
    Commented Sep 20, 2022 at 1:48

Or is a total lack of evidence for a contrary position justification for a logical conclusion?

Not to be dismissive of very real and interesting epistemological questions about warrant, justification, and the like I would contend that when their is truly no evidence (that one knows of) in favor of a certain position it is simply not possible to "believe" it. One may want it to be true, or want it to be false. One may probably even be able to have some judgment on the theoretical possibility that evidence will be forthcoming, though more often than not this may be heavily influenced by hope.

Similarly, one may not realize that there is not evidence for a position one believes in, but by the act of believing in the position one is implicitly [mistakenly] believing that there is basis for believing it. Such a belief is based on assumed evidence, which cannot be the case when one knows their isn't any evidence. Similarly people may base beliefs off of mistaken evidence, but not evidence they know is mistaken. Of course we are probably getting close to the point whether my opinion on this matter can be tested empirically and I certainly feel it would be worthwhile research.

Regarding the substance of the dispute however I would not concede that there is a total lack of evidence but I'm quite certain that's its own discussion.


Do you put garlic around your windows every night, just in case there are vampires lurking? Do you put milk out for the potential fairies at the bottom of your garden as well? There are millions of other hypothetical mythical beings we dismiss although we can't absolutely "prove the negative" of their non-existence with logical certitude (apart from the self-contradictions in many mythological concepts).

If we should have expected to see evidence for something by now but have not, then we should conclude it probably doesn't exist. If possible evidence is rare but may occur in the future, we should consider it possible but not yet demonstrated. If there is no evidence and it will not be possible to find evidence for it in the future than it should be considered meaningless and not believable. So yes, lack of evidence can lead you to a robust conclusion.

As an empiricist concepts are valuable to me if they help make sense of the world, and meaningless or unsupported concepts are damaging as they take up my limited brainpower and time which could be used more productively. In real life we never have 100% (dis)proof of anything, but that should not stop us removing generally useless or misleading ideas from our mental toolkit.

The distinction between gnosticism and agnosticism is a false dichotomy as complete knowledge or certainty doesn't exist outside axiomatic systems and there is almost always some evidence for or against a belief. The appropriate judgment is whether you have sufficient confidence in your conclusions that they inform your everyday decisions. For example I have no more belief in supernatural entities than in the possibility that a black hole is hiding in my kettle and will swallow me up when I next go to make a cup of tea, and act accordingly. In practice sufficiently unlikely possibilities must be ignored.

Of course I could change my mind given new evidence. If the stars in the sky rearranged themselves to spell out "Ragnarok is coming next Thursday" in Old Norse I would reevaluate my beliefs about Odin (after checking I was not hallucinating). However that possibility does not mean I am a semi-theistic agnostic with the currently available evidence.


Yes, it is reasonable to infer X on lack of evidence for not X, under specific contexts but not in general.

Suppose you see a hundred crows, all of which are black. You would be reasonable to infer that all crows are black (maybe even going so far as to define a crow to be black, including it in the defining characteristics). This works in the Bayesian statistical inference method. But that is no guarantee that absolutely no crow will appear that is not black.

This is related the hypothesis about the closedness of the set of data under consideration. One can assume the Closed Word Hypothesis, which means, in the set of data at hand, if A does not appear, you are allowed to infer (or really, you know) that -A is true (or -A must appear). The Open World Hypothesis says that you only know of things stated not about unstated things (but then Bayesian methods apply, you get more and more confident that -A is true the more times you do not see A).

It is a classic blunder of Hegel's (sorry, a classic myth about Hegel) that he said that there could be no more than seven planets, and in the same year as this proclamation, another planet was discovered. (It's so much more complex than that: the 'planet' was Ceres, Hegel 'proved' that Bodes Law was not correct not that there were no planets beyond Saturn, but the asteroid belt (which Ceres is a part of) fulfills the numbers of Bode's Law.)

But anyway, there are some negatives you can prove and some you can't. You can prove that there are no primes that are both even and greater than 2. You can't prove (experientially) that there an X (with consistent properties) doesn't exist in an unexplored area.

Then again, here is the classic informal disagreement between Russell and Wittgenstein, where Wittgenstein claimed that there is no evidence that there is not a rhinoceros in the room, and Russell took a more practical tack.


Is it reasonable to arrive at a conclusion based on lack of evidence to the contrary?

Yes, especially if there are no rational and compelling reasons whatsoever to assume that what is lacking is evidence.

For example, somebody tells you to sit at a table and knock 16 times, then a ghost will appear. Do you try it? Maybe. It turns out it doesn't work. The next day the same person tells you it was his fault because you must knock 17 times. And so on.

This shows that we just do not have enough time to think about, let alone disproof every silly possible hypothesis. If someone claims something, then he also has the burden of proof. That's about it.


I am a strong agnostic. I am not an atheist because first, I do not believe that a negative can be proved, and second, I believe that in this unexplored universe or some other, there is a tiny possibility that a diety is running around somewhere. When I see the atheist "flying spaghetti monster" argument, I simply acknowledge that I have no way of disproving his existence either. At our current state of development, definitively believing that there is no deity at any time or any place anywhere fails for lack of evidence, as does the opposing view. We have yet to explore 99.999% or more of the known universe, and no other universes within the postulated metaverse, so it is premature to draw any theistic or atheistic conclusions through inductive or deductive reasoning. The search is in it's embryonic stage. So often I find myself told that I am "in between" which I think you have done a wonderful job of debunking. So for the moment I am back to searching for a god or at least a superior life form. Since I am not an astronomer, I so far have been limited to looking behind the couch and under the bed. No luck so far, but I have a long way to go to attach myself to one side or the other.

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    You seem to imply that the search for God should be undertaken by astronomers, or that science may somehow prove the existence of a deity. This is a little unclear to me.
    – Joseph Weissman
    Commented Jan 7, 2012 at 19:12

I was having a discussion last night about my atheism, and it was suggested to me that agnostism is the only reasonable conclusion, as it leaves the door open for new information.

Why would "leaving the door open to new information" Make any view on religion(s) or world views seem more or less reasonable (Which I assume just means true) Again whether some position is open to new information and whether it is true or not is not a related question.

Even if a certain world view is not open to new information it can certainly still be true. The inverse is also true. It is also entirely possible for a world view to be open to new information and still be false.

The person you talked with seems to confuse the issues.

This made me think, were they right? Or is a total lack of evidence for a contrary position justification for a logical conclusion?

Though it true that their is the maxim that lack of evidence is not in itself evidence for a positions falsity I would like to add that the more apt conclusion in such a case would be...

1) to either assert that the evidence is insufficient to make a conclusion and hope that more evidence arrives at a later date.


2) Decide that the method that you where you are using is inadequate to investigate the proposition and propose a better one (If such a thing exists).


Depends on what how you define "reasonable", upon whether you'd expect to find evidence and on it being a true binary.

Like first of all what do you mean by reasonable. Do you want the truth and nothing but the truth or are you content with something that is "close enough"? If you want the former than obviously you're lack of evidence needs to be conclusive so not just "I haven't found something" but "There cannot under any circumstances BE something" (and not as a "believe" but as a provable fact).

Secondly. Like if you're expecting to find Venus matter on earth and dissatisfied that you don't find any conclude that Venus doesn't exist, that would obviously be nonsense.

Thirdly, if you'd conclude from the lack of evidence for the existence of one particular deity that atheism is true, you'd neglect that you could make up all sorts of deities for which the lack of those particular evidences does not conclude the nonexistence. So you're essentially pretending it's a binary when it's not.


Well, if you're an athiest - you're an athiest. What's exactly the problem with that? It's probably been a minority option for most of the hostory of the world but in todays secular Western culture it is a favoured option for many. So you've chosen that path.

Most people who are religious are so because of scripture or have had minor or major religous experiences which convinced them. I met a Christian lady who converted from Hinduism to Christianity because she felt the real presence of Christ. That's her religous experience. You obviously have had none.


Short Answer

No, as a general rule, it is not appropriate to accept a view solely due to lack of contrary evidence. This is a known fallacy, and it is called an argument from ignorance.

A Bit Longer Answer

Generally, what one must have to believe a proposition is an accumulation of evidence (or support) FOR the proposition, sufficient to justify belief in it, PLUS weak or no contrary evidence or justifications against it, PLUS sufficinet evidence or support against all the competing options to the proposition, such that the original proposition is more plausible than all of the other options.

But this is philosophy, so of course I am not done yet

Most atheists today try to avoid making an evidential case for atheism. There are a variety of rationalizations that I have seen, to try to avoid the work needed to do the bit longer answer above. I will discuss a few:

  1. One is the assertion that atheism is a NEGATIVE claim, and negative claims do not need to be supported, only positive claims do. However, this is an untenable assertion, one can craft any claim linguistically to be positive or negative. Both positive and negative claims are about our world, and claims about our world need to be supported.
  2. Second, to supplement the first, is the claim that negatives can never be "proven". This is silly too. Almost nothing can be "proven" so there is a red herring in this assertion to start with -- empiricism operates upon "support", not proof. And science supports or contradicts negatives all the time. Hypothesize an effect, derive a predicted consequence, then test for the consequence. If you don't find it, that is significant support for a "negative" of the original claim.
  3. Third is the idea that the universe is too big to examine all of it to find something which may be hiding. This is silly for most claims -- they include details that specify where one would find something, so look in those places. For a God claim, an example would be where the God is a claimed Creator -- look at the claimed creation for the tells of agency and intelligence in design. If they aren't there, this is significant support for the negative of the God claim.
  4. The claim, which you repeat here, that there is no evidence for any God. This claim is blatantly false, and any even minimal study of the beliefs of any religion would readily reveal this. Miracle stories, recent miracles, mystics with personal experiences, narratives about the extraordinary nature of the founder, etc are all support -- evidence.

I will discuss later what these false rationalizations say about the atheists who espouse them.

I am not an atheist, but I know the basic rationale for the view:

  • If one applies tests like in 3) to the top 5, or top 10 or so God claims in the world, then I believe one can reasonably infer that each of them has sufficient contradictions to reject them.
  • This makes it plausible to infer that one is likely to be able to eventually do this for all God claims, and it is therefore reasonable to infer they are all significantly contradicted
  • And there is an alternative ontology, that of physicalism, where there would be no possible Gods, and this is a credible ontological view
  • And there are psychological reasons why people might delude themselves into thinking there is/are God(s), which could explain the widespread belief in them by what seem to otherwise be reasonably competent and rational adults.
  • The above list encompasses all of the alternatives to atheism.

The justification is generally longer when done with gusto, and will have other supporting elements as well, but the above is a pretty good summary, and MUCH stronger than the four invalid rationalizations I noted earlier.

Providing this, or a fleshed out stronger version of this case, would be a far more effective defense of atheism vs. the position of indeterminacy your friend was advocating for you.

Note you and your friend misused agnosticism. You two were applying three state logic (proposition justified, not sure of justification, proposition rejected) to the God Exists claim. But actual reasoning is four state (proposition justified, not sure of justification, preposition rejected, preposition incoherent or unevaluatable). For God Claims Agnosticism is the name for the fourth state, and indeterminacy or uncertainty is the second.

Again, this is philosophy, so no answer is simple and this one is still going.

As I noted, every religion cites justifications and evidences of their particular view. Many of these evidences lead to apparent contradictions between religions. This is bad for specific religions, but not necessarily bad for religion as a whole, and this is a major problem for the argument I listed for atheism. An OPEN MINDED theist could take those evidences, and say "yes, between the contradictions of evidences, and refutations of specific religious claims, none of the 5 or 10 or whatever religions examine carefully actually match this data fully. But this data supports that there IS some spiritual universe out there, with spiritual agents in it, even if the major religions' claims are flawed." This argument challenges the second bullet in the case I outlined.

The third bullet, physicalism, has a lot of problems to it, what with the Hard Problem of Consciousness, the growing consensus of the reality of abstract objects, and Hempel's Dilemma making physicalism undefinable.

The last -- can easily be reversed upon atheists. See the list of rationalizations I discussed at the outset. Atheists asserting rationalizations to support what they want to believe -- are as real and common a phenomenon as religious rationalizations. ALL humans are subject to confirmation bias and motivated reasoning. And every one of us should realize we may be subject to it in our core thinking.

I am not endorsing your friend's "indeterminacy" suggestion for you. This suggestion, that no atheists can credibly claim "knowledge" is one I have repeatedly seen from bad theist apologetics. The answer to those apologetics is the bullet list, I offered, or something similar. I assume that something like this bullet list is why you are an atheist, so lay it out there.

However, I AM suggesting that your reasons may not be as solid as you may imagine them to be, and the correct approach for a rational person, is to examine those assertions CRITICALLY, like an opponent would, rather than lovingly, like a motivated thinker would. Be sure you search for the hard cases, that might upend your thinking, rather than just for the reinforcing examples that will harden it.

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