I heard people having this kind of discussion. I don't know why it sounded a bit off, but I want to know if it was just me or if there is a fallacy here somewhere.

Person 1 = X

Person 2 = Y

X: Aliens do not exist because God did not mention them in the Bible.

Y: You can't say that because maybe God mentioned them in some other book that is not in the Bible. For example, there is the Book of Enoch that talks about God punishing angels who sinned on earth. Did you know that God did that?

X: No.

Y: So, how do you know that God did not mention aliens in one of those books that are not in the Bible or said it in a book that has not yet been discovered?

X: ........

It sounds like person Y is making some sort of appeal to ignorance. Is that the case? Are there any other fallacies involved? Or is this discussion perfectly rational?

  • 4
    God didn't mention dual-mass flywheels in the Bible ? Do they exist ? :P
    – rs.29
    Commented Feb 3, 2019 at 15:58
  • 2
    @InertialIgnorance A premise can not be fallacious, it can only be false. That has no bearing on whether the argument is valid or invalid, i.e. fallacious.
    – Conifold
    Commented Feb 4, 2019 at 6:41
  • Ironically I actually believe it's scientifically impossible for aliens to visit our solar system. Genetically, they wouldn't be able to see very well in our sun's particular light spectrum, so it wouldn't be much fun for them. Food might also be a big problem for them.
    – Bread
    Commented Feb 5, 2019 at 2:53

3 Answers 3


There is a fallacy, but it is not being used by one of them against the others.

There an overall appeal to authority here that both have bought into. They just disagree upon whether that authority should be the Bible, or all 'inspired literature' about God that passes some other test. (There has to be some test, or you quickly get to a much better argument: the Ramayana and passages about spaceships. What is the point of a spaceship without aliens? Who would Rama go visit?)

Either that, or this is taking place within a context where a premise of fundamentalist literalism is accepted as an open premise. That would be a rare context these days, but still easy to find.

This argument by 'Y' is not unheard-of on a larger scale. There are definitely traditionalist Mormons who take a fundamentalist literal view of the world. But given their origin story, they then have to accept the notion there are probably undiscovered scriptures in addition to both the Bible and its Mormon extensions. So there might then be more...


X's argument seems to contain the implicit assumption that if something is not explicitly mentioned (or implied) in the Bible then it must not (or more charitable, probably does not) exist. This assumption is clearly suspect. Essentially, X's argument is the one committing the fallacy of appealing to ignorance:

The assumption of a conclusion or fact based primarily on lack of evidence to the contrary. Usually best described by, “absence of evidence is not evidence of absence.” - logicallyfallacious.com

Just because there is no evidence of aliens in the Bible, doesn't mean they don't exist. There are several ways one could further respond. From a theological standpoint, I'd argue that it's implausible to assume that God told human beings everything there is to know in the Bible. The Bible is a book meant to communicate the story of God's redemptive process through history for humans, not a cosmic encyclopedia of all knowledge.

Now, you say that it seems Y is making an appeal to ignorance. I disagree. Notice Y is simply saying X is unjustified in believing the proposition that "because the Bible doesn't mention aliens, they don't exist" because his assumption which I stated above is false. Y then offers counterexamples. There is nothing fallacious here. Y isn't saying, because X has no evidence for his belief, then the converse belief is automatically true.

In another vein, one could argue that the entire discussion between X and Y is fallacious because they're both taking for granted the proposition "The Judeo-Christian God exists", as I've seen some point out. Again, I would have to disagree. The reason it is taken for granted that God exists is that the discussion between X and Y implies both X and Y are Christians. Thus, they both already accept that God exists. If both parties in an argument agree to take certain propositions for granted (as X and Y seem to implicitly do), no fallacy is committed by either party by assuming the truth of the said proposition.

The fallacy only comes when one party in an argument takes for granted a proposition that has not been argued for or the opposing party has not agreed to accept. If X was a Christian and Y was an atheist, then the discussion between X and Y would be fallacious since X is assuming that God exists in his argument, which is a point Y would contest.


Here are the fallacies I can spot :

X: Aliens do not exist because God did not mention them in the Bible.

There is a formal fallacy which is a Denying the Antecedent , I assume person 1 would agree with the conditional if God mentioned A in the Bible then A exists, but they would be a fool if they agree with the conditional if A exists then God mentioned A in the Bible, since there are many things that exist, and that we know exist, which are not in the Bible (like planes and computers).

So, I would take person 1 seriously and assume they are not a fool, in this case they agree only with the conditional if God mentioned A in the Bible then A exists. And I would give the propositional form of their argument :

  • Premise 1 (implied): If God mentioned Aliens in the Bible then Aliens exist
  • Premise 2: God did not mention aliens in the bible
  • Conclusion: Therefore, aliens do not exist

If P then Q , Not-P therefore Not-Q : This was an invalid argument.

Of course, either Person 1 is a fool to think that if x exists then it's in the Bible, or they are not a fool and they have just committed a denying the antecedent fallacy

So, how do you know that God did not mention aliens in one of those books that are not in the Bible or said it in a book that has not yet been discovered?

What is in bold is probably an Appeal to the ignorance.

  • I don't think Y's response is Appeal to Ignorance. Y isn't arguing that aliens exist, he's arguing that aliens could exist. In fact, X's argument is closer to Appeal to Ignorance than Y's argument. If we assume X's Premise 1 is correct, then he's arguing that "because we don't know if more books exist, they don't exist." (at least that would be the counter argument to Y's argument) Commented Feb 4, 2019 at 3:15
  • Y is deleberately trying to make the fact that scriptures did not mention aliens less certain, it would be like me arguing that you cannot say that we have one moon, because maybe there is yet another moon hiding behind it and we will discover it sometime in the future. It does not matter if you try to prove something or to make a fact more confusing : I think it is an appeal to ignorance, or at least: there something wrong with it.
    – SmootQ
    Commented Feb 4, 2019 at 7:47
  • You appeal to ignorance when you use uncertainty or ignorance to prove X, here X is not "the books mentioned the aliens", but "the fact that the books didnt mention the aliens maybe is wrong" ... this is a clear appeal to ignorance
    – SmootQ
    Commented Feb 4, 2019 at 7:51
  • 2
    Presupposition is the basis of argumentation. If arguers both accept A, then it doesn't matter how A was determined. There is no fallacy in this case.
    – a1s2d3f4
    Commented Feb 4, 2019 at 18:48
  • 1
    @a1s2d3f4 I kind of agree with you after much thought, I corrected my answer (and removed all the fallacies that maybe are irrelevant), thank you
    – SmootQ
    Commented Feb 5, 2019 at 14:14

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