Idk where else to ask so sorry if I am wrong to ask here...But this place seems fitting.

A Fallacy, both formal and informal is/are error in the reasoning to reach a conclusion for an argument/point/belief. Yet, if you assume that conclusion is wrong because it have fallacy, that in itself is wrong and fallacious, specifically "Fallacy Fallacy".

But what if it's the other way around? What if people assume that since the conclusion of an argument or a point or a logic is wrong, there must be a fallacy?

For example take this

  1. Cyanide is a poison
  2. This drink have Cyanide in it
  3. This drink is poisonous.

Now this is sound and valid. However you can make it sounds like it is fallacious. For example; assume that there is a drink with Cyanide on it but also brewed in a way that makes it non-poisonous. That would imply this conclusion of this set is wrong. But is it fallacious? what if the person who made this set just didn't know that non-poisoned-Cyanide-drink exist? Assuming such drink did exist that is.

Another example.

  1. This hot chocolate is made of vegetable; chocolate
  2. Vegans only drink vegetarian beverage
  3. This hot chocolate can be drunk by Vegans

This is actually true in some cases, and not true in some cases. Some hot chocolate may have milk which is not vegetarian. If a vegan is given a hot chocolate with milk, and that person didn't know there is milk, nor ask, that vegan is wrong but is it fallacious? However it is also possible that the vegan is given a hot chocolate without milk.

In both cases, there is a lack of information that may make their logical conclusion to be false. And sometimes it's actually quite rare for the exception to that logic to exist, such as the Cyanide example. While you can say that their fault is due to their lack of information, I don't think it is fair to immediately blame someone for lack of information for something that can be taken at face value, such as those that involves "Rule of Thumb". It is quite unrealistic to demand someone to know everything about anything about beverages to make simple judgement such as drinking a drink. That doesn't change that they can be wrong though.

Yet another example, when you order a juice at a restaurant, and then you are given the juice you ordered. You "assume" that the juice is safe, turns out the juice is poisoned. That means the conclusion is wrong, yet does that means there is fallacy in your judgement? It's quite unrealistic and overreaction to doubt every drink given to you just because there is a small chance it can be poisonous. So I don't think there is any fallacy here despite the premises here are all logically true and valid.

I don't think simply having the wrong conclusion means there is an error in the reasoning for it to be fallacious, yet I don't see anyone talk nor there is article about it. So I am curious what other's think.

What do you guys think? Can something have true premise(s), but wrong conclusion and yet no fallacy? Is it fallacious to assume that because the conclusion of point/belief/argument is wrong, there must be a fallacy? If so...What is the fallacy called?

  • You're analyzing syllogisms of formal logic within the context of practical, real world scenarios. In the real world, there are other assumptions/axioms to take into account rather than the clean ones you state. The way you're talking about some of these things also indicates a multi-valued logic may serve best in formal analysis. I would suggest looking into more advanced and technical logic to answer your question that way. In short though, while your idea is wrong in terms of formal logic, there is some practicality to it for real world thinking. Dec 17, 2022 at 6:37
  • Thanks for the suggestion but I don't understand how is the idea wrong and what do you mean "practicality for real world thinking". I don't think it answers the question if it is fallacious for someone to assume "If the conclusion is wrong, then there must be a fallacy". Dec 17, 2022 at 6:51
  • If the conclusion of a logical argument is wrong, then either there is an error in the argument or the system of logic itself is inconsistent. Note that the conclusion being wrong of course means that there is some verified argument which concludes the negation of it. So it is not fallacious in any formal, abstract thought. In the real world however, noting every implicit assumption being made and every confounding piece of information to consider is impractical and likely even impossible. In this case it may be fallacious, as things are verified via empiricism rather than deductive reasoning. Dec 17, 2022 at 7:00
  • After re-reading, it seems I misunderstood the comment. So in Formal Logic it would be not fallacious but in real world logic it will be fallacious to assume just because something is wrong it is instantly contain a fallacy? But wouldn't that fits with rationalism as well? Not just empiricism? Dec 17, 2022 at 18:30
  • Don't do that thing/thing/thing pattern. What it does is needlessly confuse your point. For example, argument, point, and belief are three things that are not synonyms. So two of them are probably totally wrong for your question.
    – BillOnne
    Dec 17, 2022 at 18:45

5 Answers 5


There are two errors that can be identified in these arguments. I'm not sure whether they count as errors in formal logic.

Consider this example:-

  1. This hot chocolate beverage is made of vegetable; chocolate
  2. Vegans only drink vegetarian beverage
  3. This hot chocolate can be drunk by Vegans

I've tidied up premiss one because it could be thought to be ambiguous between the contents of the tin and the contents of the beverage.

The first error is well known; it is called a suppressed premiss:-

2a. There is no ingredient other than chocolate in this beverage.

If the other error has a name, I do not know it. It is that premiss 1 turns out to be only partly true. It should read:-

  1. This hot chocolate beverage is made of vegetable; chocolate, and nothing else.

In your first argument premiss 2 should read:-

  1. This drink have Cyanide in it, brewed in a way that makes it non-poisonous.

You don't need to make both changes to each argument. One or the other will do the job.

I don't think there is any way to formally guarantee that a given argument does not contain these errors if any of the premisses is empirical.

If you are formulating an argument in real life, there is an expectation that you will exercise reasonable care to ensure your premisses are complete and wholly true. If you have done that, you are not to blame for any errors.

Yes, it would be unreasonable to doubt every drink given to you because there is a small chance it is poisonous. You are entitled to count on the person you buy the drink from that they have given you accurate information about it - and that person is entitled to count on manufacturer's information as true and complete.

  • Ah tnx, I just can't think of any other example and just go with beverages... But I was using that set to illustrate a vegan who was given a hot chocolate, they think hot chocolate is safe because chocolate is vegan and they didn't think of asking if it got milk. If it turns out that it got milk, that means they are wrong. But is it fallacious? That is my main question. Does every wrong conclusion, such as mistake, as we as humans always makes mistake, must be fallacious? can a wrong conclusion have no fallacy? I don't think it is ever talked or stated if a wrong conclusion can have no fallacy Dec 17, 2022 at 18:28
  • @FlippeRFlappeR. If an argument is valid and its premisses are true, then the conclusion must be true. It follows from that that if a conclusion is not true, either the argument is not valid or the premisses are false. If the premisses are incomplete, as in your examples, the argument is not valid (suppressed premiss). Premisses must be either true or false (Excluded Middle); a premiss that is partly true does not count as true, but as false. Does that help?
    – Ludwig V
    Dec 17, 2022 at 21:12
  • Somehow I don't think you get what I mean. Does your comment here mean that if you make a mistake you immediately make a fallacy then? Again, like for example mistaking something someone give you for another thing? Do you make a fallacy in that situation? My main question is still, if you make any mistake in your conclusion, does that inherently means there is a fallacy? Dec 18, 2022 at 7:10
  • @FlippeR FlappeR. Well, it is absolutely clear that if your premisses are all true and the argument is valid, the conclusion must be true. If it isn't true, either your premisses need correction or perhaps an additional premiss or your argument isn't valid. From a certain point of view, that could be regarded as harsh, but soundness and validity aren't a reward and unsoudness or invalidity are not a punishment. There's no value judgement attached to failure.
    – Ludwig V
    Dec 18, 2022 at 8:49
  • I don't understand...I don't think there is anytime where I talk about punishment and reward. I don't know where did that come from. And yes, a person may misunderstood if the premise is lacking or need correction, does that means it is correct for someone else to claim that person is making a fallacy; because that person misunderstand? I still don't think you answer my question. Misunderstanding is a wrong conclusion over another person's point or speech. If you have the wrong conclusion, does that means you inherently makes a fallacy? And is it fallacious to claim such? Dec 18, 2022 at 8:59

For example take this

Cyanide is a poison

This drink have Cyanide in it

This drink is poisonous.

Now this is sound and valid. However you can make it sounds like it is fallacious. >For example; assume that there is a drink with Cyanide on it but also brewed in a >way that makes it non-poisonous. That would imply this conclusion of this set is >wrong. But is it fallacious? what if the person who made this set just didn't know >that non-poisoned-Cyanide-drink exist? Assuming such drink did exist that is.

Your initial argument rests on the premise that Cyanide is a poison. If you now assume that there is a drink with Cyanide on it but also brewed in a >way that makes it non-poisonous, then you are falsifying the premise that Cyanide is a poison since it now depends on whether it is or not brewed in a >way that makes it non-poisonous. Adding a new premise changes the argument. In other word, if you add a premise, it is a different argument. In this instance, we all see the initial argument as valid because we all assume that a poison is always poisonous. Your new premise means that a poison remains a poison even though it is possible to make it non-poisonous. However, if we accept this premise, the new argument is clearly fallacious:

Cyanide is a poison

Cyanide can be brewed in a way that makes it non-poisonous

This drink has Cyanide in it

This drink is poisonous.

The drink is not necessarily poisonous if the premises are all true.

  • But I don't think it answers the main question. Can something with wrong conclusion be non-fallacious? The example with Cyanide was just to illustrate that thinking "Cyanide is poisonous" should be normal, but assuming the person didn't know there is a non-poisonous drink with Cyanide on it, is it fallacious for that person to instantly think Cyanide is poisonous? Dec 17, 2022 at 18:24
  • @FlippeRFlappeR "Can something with wrong conclusion be non-fallacious" A non-fallacious conclusion is trivially true because"non-fallacious" just means "not false". 2. ""Cyanide is poisonous" should be normal" And it is normal but it was you who introduced the additional assumption that cyanide may not be poisonous while keeping the same conclusion. Now, that is logically fallacious. If you want to make sure there is no logical fallacy in your argument, you need to include in the argument itself all your premises, something you failed to do. This is the correct answer. Dec 18, 2022 at 10:34
  • Okay for the Cyanide, it feels like using that example just convolute the point now. But what about the chocolate milk? Lets say a vegan is given a chocolate drink by someone they trust. And they didn't think of asking if there is a milk in it, and let's say they didn't think the chocolate drink may have milk in it. That means they made a mistake. If someone said they make a fallacy because of that mistake, is that correct? because they have the wrong conclusion. Does that mean that everytime we make a mistake we made a fallacy? And what does "Trivially True" means in this context? Dec 18, 2022 at 10:39
  • @FlippeRFlappeR 1. A fallacy is just a false statement or idea. An illogical argument is called "logical fallacy", not "fallacy". 2. False conclusion does not imply logical fallacy. 3. Logical fallacy is illogical reasoning. Whether the conclusion is true or not is irrelevant to whether the argument is a logical fallacy. An argument is a logical fallacy if the conclusion does not follow logically from the premise. If the premise is "Hot chocolate is made of chocolate", then it may have milk in it. If it is "Hot chocolate is made of vegetable", then it doesn't have milk in it. Dec 18, 2022 at 16:25
  • "False conclusion does not imply logical fallacy." This is something that I've pick up from seeing multiple debates in Internet. While no one say it outright, it does feels like people think if a conclusion is false, it definitely have fallacy. My question is about this. Is it fallacious to think so? Can't a false conclusion have no fallacy? And I agree about Logical Fallacy is Illogical reasoning. Also Chocolate is vegetable, so saying "Hot chocolate is made of vegetable" while technically not the same as "made of chocolate" it is practically the same. It may still have milk in it. But tnx. Dec 19, 2022 at 4:19

If the conclusion follows from the premises then true premises necessitate a true conclusion so if that is not the case it's a fallacy. As the truth of the condition is not a consequence of the premises (either because they don't determine it or because there are non-stated factors that contribute to determining it).

In the example with the cyanide the fallacy is, as others have mentioned, that there is a hidden premises of "mixing a poison with another substance preservers the poisonous quality". Which isn't necessarily true, like if you mix a poison and it's respective antidote would not be poisonous.

The other relevant point here is that poisonous effect doesn't follow from the presence of a poison to begin with. It depends on the dose, the person who takes it, their immune system and general constitution and so much more. So it's not even valid to begin with that consuming a poison is poisonous.

While if you use a non-standard definition of anything with added poison is poisonous then even brewing it so that it loses it's effect would still mean it's poisonous (as it still contains a poison).

And the 2nd example is essentially:

Hot chocolate is vegetarian
Vegans only consume vegetarian food
Vegans could consume hot chocolate

The problem is that while the first 2 statements are true that does not necessitate that the conclusion is true. Like the obvious problem is that vegan is a subset of vegetarian so a vegetarian could eat all that a vegan could eat but not the other way around.

So for it to be valid, it would need to be:

vegans could eat everything that is vegetarian
hot chocolate is vegetarian
Vegans could eat hot chocolate.

That would be incorrect but it would valid. The fist isn't even valid as the relation between vegan and vegetarian isn't stated in the argument, yet is what the success or failure of it relies upon.


@FlippeRFlappeR, I believe @Ludwig V is spot on. If an argument is valid and its premises are true then, the conclusion is necessarily true.

This means if the conclusion is false,

1)the argument is invalid


  1. the premises are false.

Fallacies are, to my reckoning, about invalidity and so look at possibility 2 (false premises). It is possible that an argument 1) is valid (nonfallacious) 2) can have a false conclusion because the premises are false.

For example look at this argument:

  1. If Dogs are fish then dogs have gills

  2. Dogs are fish


  1. Dogs have gills (1, 2 modus ponens)

The argument is valid (modus ponens) i.e. it isn't fallacious but it has a false conclusion (dogs have gills), just the kinda situation you were describing.

  • False Premise is connected to Fallacious argument like your example, because Dogs are Fish is False Premise. So I am not talking about argument from that either. And Fallacy can exist from something other than False Premise. I've said it in another comment, it feels like people in internet think that if a conclusion is false, it definitely have fallacy. "Your conclusion is false, you must've commit a fallacy". I am skeptical about this, hence my question. Misunderstanding also exist, can you call that a fallacy? or lack of information? etc.Anyway the other person answer this already...I think? Dec 19, 2022 at 6:46
  • "Your conclusion is false, you must've commit a fallacy". That statement isn't necessarily true (in my answer, I gave an example of a valid (nonfallacious) argument with a false conclusion due to false premises. Dec 19, 2022 at 6:49
  • Yes, thats not actually a statement I make. That was what I feel like the belief around the internet is, I just say it to illustrate my point. But I don't agree with your example. Your example also sounds sounds fallacious, because False Premise is related to fallacy, some would even call it informal fallacy, so I am not talking about False Premise. A 2 true premises can create a false conclusion by misunderstanding, would you call that fallacious? My question isn't necessarily just for Argument and syllogism, but also belief and decision and actions and points, etc. Dec 19, 2022 at 6:54
  • How does one misunderstand a proposition? Dec 19, 2022 at 7:49
  • Depends on what you mean a proposition. But my point is, if Person A said "Alex is a Bachelor" for example, a Bachelor can either means a degree or a virgin male. If Person B ask "Bachelor of what?" because Person B misunderstand and assume the Bachelor is a title instead of a virgin, do you think that is fallacious? Of course depending on the context, it could be, but does it inherently means Person B commit a fallacy? Such as Equivocation? Because this is to illustrate that Person B misunderstand what Person A is saying. The character limit kinda makes it hard for me to explain more ... Dec 19, 2022 at 11:23

After reading every answers, I've gained new knowledge. Ironically, my new knowledge only strengthen my belief. I know this sounds like self-righteous, but that is truly what I think after searching.

Thanks to Joseph I've start to look more towards Formal and Informal logic and how they apply for real world logic. Thanks to Ludwig I've search internet more for "Mistakes". Like Joseph said, in formal logic it is not fallacious to say "If there is a wrong conclusion, there is a fallacy" but in real world logic, it may be fallacious to say so. Mistakes happens, that is human nature.

There are intentional and unintentional, and Fallacy is intentional. Factual Mistakes for example is not inherently a fallacy. It could be a misconception which is similar to False Premise, or it could be another unintentional mistake. For example if you search for Factual and Logical mistake online, you will get an example of counting 20 people in a room when in reality there is 21. That is factual mistake not from False Premise but rather a Factual Mistake from miscounting.

A misunderstanding can happens due to a Fallacy, and a Misunderstanding itself can cause a fallacy, but is it in itself a fallacy? Misunderstanding can be due to a lot of things, like in my bachelor example. Fallacy is Error in Logic, Misunderstanding can happens due to correct logic just not in line with the other person, or due to language barrier. I don't understand how could someone said Misunderstanding is a fallacy...

There is also the case of forgetting something can make us make a mistake. I hope people don't think forgetting something is a fallacy either...

But this question has actually does convince me that people do think Wrong Conclusion means Fallacious argument. A "Fallacy" is a mistake but doesn't means a "Mistake" is instantly fallacious. I belief this in itself is jumping conclusion and fallacious. I know that there will be people who may not agree with this but using real world scenario usage that informal logic to be more for, it seems to be the case.

So yes, I don't know if I misunderstand what Joseph said, but it sounds to me like he is saying: In Formal Logic where only the soundness and validity of a set matters, it is not fallacious to say if there is a wrong conclusion there is a fallacy. But in real world logic where there are more variables it may be fallacious. And after doing more search, I agree with that.

Conclusion: Not all wrong conclusion is inherently fallacious. Context matters. Although I suppose some who disagree with me may think this conclusion is fallacious...Maybe there is another way that better explain this but I strongly belief this is the answer.

  • 1
    A fallacy is not just a mistake, it's faulty reasoning. So something is wrong with your argument so that the conclusion doesn't follow from the premise, i.e. is invalid. Whether you do that intentional or unintentional is unsubstantial to the question whether or not it is a fallacy. What's judged is not your character but the strength of your argument. And the real world just makes it more messy. Like in binary logic it's either true or false in the real world the truth value of any statement is borderline impossible to determine and could take more than 2 states also language is ambiguous...
    – haxor789
    Dec 21, 2022 at 11:39
  • ... That being said if you'd take the time and sort things out, remove the ambiguity, propose definitions and only use the logical operations that are defined in that space, so that you still operate in the realm of deductive logic, then it would still be a fallacy.
    – haxor789
    Dec 21, 2022 at 11:42
  • Fallacy is a faulty reasoning yes, and the act of using fallacy is a mistake. Also intentional and unintentional is substantial regardless of your denial. Otherwise, by your logic misunderstanding is a fallacy when it's not, or forgetting something is fallacious when it's not. The context of your "argument" matters too. And I am not just talking about Argument, also believes, interpretations and points, etc. When we are talking about those outside of syllogism that we encounter on our life, those "real world" logic matters and not borderline impossible like you claim. Dec 21, 2022 at 12:37
  • A fallacy is not a personal flaw or mistake it's faulty reasoning. So if you misunderstand something, interpret a premise the wrong way or if an important detail is left out and thus the argument doesn't work, then you've encountered a fallacy. Because the argument doesn't work. Whether that is intentional, hostile, accidental or whatnot doesn't matter, you've found a flaw that you could point out upon which the other person can clarify or update their claim.Beliefs and interpretations etc only get more messy in terms of whether you can apply the idea of a fallacy to being with.
    – haxor789
    Dec 21, 2022 at 12:46
  • I said in the other comment, Fallacy is faulty reasoning, yes and the act of using Fallacy is a mistake. I simply cut it short in my answer above when I said Fallacy is a mistake, but I divulge more in the comment. And what fallacy is there in misunderstanding? In my Bachelor's Example. A and B were talking about Alex and A said Alex is a bachelor, B ask bachelor of what? What fallacy is there? How, when the logic fits? Bachelor can both means virginity status and degree, and A wasn't clear in what A means, B's logic and reasoning is not faulty even when B misunderstand what A means. Dec 21, 2022 at 13:09

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