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Magical Thinking launched as You Fail Logic Forever Discussion: From YKTTW

Working Title: That is illogical: From YKTTW

Indigo: Whoever wrote the entry on the fallacy of composition got the definition basically right and then proceeded to provide examples that did not fit it at all. I'm not even sure what kind of fallacy "this state contains many divorced people and many religious people, therefore many divorced religious people" is, but it's not a fallacy of composition. Replaced it with the classic invisible atoms/invisible matter example. Also moved the Wild Wild West example to fallacy of composition, since it's definitely not fallacy of division.
Is the Judgment of Solomon really an 'argument to moderation'? It's tempting to think so, since he threatens to chop the baby 50/50 and all, and it is if you characterise the women's demands as "I want 100% of that baby", but even if you do, that ignores the very obvious implication that they want that baby alive, and Solomon cannot even pretend to strive for moderation in that aspect. I think that ambiguity is enough not to include it as an exemplar of 'argument to moderation', so [edit: I've just deleted it, there's already a clearer example there]. Curious to hear counterargument though.

Should we make a rule to only use abstract examples for these arguments? I'm seeing a lot of arguments here smell a lot like somebody just wanting to see a position they disagree with listed as a logical fallacy, and this is a flame war waiting to happen. Example:

  • X has never happened yet, therefore it can't happen. Very popular with supporters of nuclear power. They say Three Mile Island doesn't count because it was only a partial meltdown, the full meltdown was averted through luck (but they would say it was the design). Chernobyl doesn't count because that was a different type. Since no Western reactor has had a meltdown, it can never happen.

If somebody says that nuclear power is dangerous, pointing out the consistent pattern of safe operation by nuclear power plants is a logical response. What would you call this supposed logical fallacy? Appeal to facts? Logically speaking, if you wish to demonstrate that X happening is not outside the realm of extreme possibility, the burden of proof is on you to show that it is possible. Otherwise, you are asking somebody to prove a negative, which is generally accepted to be a true logical fallacy. I don't really see any reason for this one to be here other than somebody wanting to bash nuclear power on the page.

Fanra: I agree that I made it too long and too much of an attack on nuclear power. Therefore, I put it back with only a short mention of it. It is not asking someone to prove a negative. There is a big difference between "nuclear plants have run in the USA for 60 years without a meltdown" and "we have never had one and that proves that we have the technology so that we will NEVER have one". If you need examples besides that, if nuclear power is too much of a Flame War subject, I'm sure we can find others. But it is harder to get people to understand if you use something like, "We have never had a nuclear war (both sides with nuclear weapons) so we never will" because most people don't feel so sure about that.

But it is a real logical fallacy. Perhaps it should be, "We have never had a flood here so we never will" based on the recent Iowa flood of 2008. A number of people were quite upset that the government never told them to get flood insurance, because they didn't live in a flood plain. Apparently, living in a 500 year flood zone (estimated chance of a flood every year 1 in 500) was not good enough to save them.Confusing, isn't it?

No, it really isn't. If you live in a place that will only flood every 500 years, then flood insurance probably isn't too good of a deal. You're actually engaging Historian's Fallacy (; unless there was significant evidence that a flood was likely to happen soon, then it was more logical to assume that a flood wouldn't happen. If the 500 year estimate was off, then they were operating off of false information, not a logical fallacy. Without the ability to absolutely predict the future, the best we can do is make assumptions based off of past observations.

You're basically tring to call inductive reasoning a logical fallacy, with a little slice of strawman to spice it up ("The likelyhood of X happening is not great enough to justify changing a course of action based on it, as evidenced by the extensive record of contrary behavior" reduced down to "This has never happened, so it won't happen").

Nezumi: Even assuming it qualifies as a logical fallacy, arguing that Nuclear Power is unsafe because some people reach conclusions about its safety based on that falls under the Fallacy Fallacy, as the facts are that most Western reactors are based on the Pebble Bed model, which, in testing, spectacularly fails to threaten a catastrophic meltdown under even worst-case scenario conditions. Nuclear power is far from ideal, but it's actually a fairly good option at the moment — it's actually comparatively clean, and fairly safe. Further research and use promises to only increase that, through new safety features, research into nuclear recycling, etc. Still, something else would be ideal. Fusion-based power that's practical, for example, or more efficient wind and solar. Or, farther out there, matter-antimatter annihilation or direct matter/energy conversion.

The Defenestrator:
  • The Left Behind novels commit this one: assume the Rapture will take place. Therefore, all the preachers who claimed the Rapture would take place were right. Therefore, the Rapture will take place.
The people who believe in the Rapture might commit this fallacy, but the books themselves don't because they're fiction, so the Rapture is just part of the premise.

bluepenguin: Should False Dichotomy get a mention somewhere here?
Janitor Pulling this, whatever it is.
  • Assumption despite massive, contradictory evidence: We know that eergy diffuses over time thus it it does not last eternally and are pretty sure that near death "exxperiences" are merely hallucinations caused by stress, electrical and chemical reactions. Most of the world however still clings to a foolish belief in the afterlife. See also creationism versus evolution.

Lull The Conqueror: Cut this:
  • Anyone who uses this is a coward and should not be taken seriously. This troper takes clear, carefully considered stances on the issues and does not appreciate those who cannot decide.
    • Right, because IN NO WAY can something have both good and bad qualities, with evidence for each. Nukes are either horrible weapons of mass destruction OR the greatest deterrent of conventional warfare. Sickle-Cell Anemia is either a debilitating life-shortening disease OR a genetic resistance against Malaria. Organized religion has either lead to discrimination, wars, genocide, and the uplifting of dangerous radicals to positions of power OR peace, charity, brotherhood, morality and an uplifting sense that we're not alone in a cold, dark, godless universe.
    • Congratulations on a wonderful example of argument to moderation combined with a strawman.

From under the "straddling the fence" entry.

Kilyle: Is there an "argument to historical hypocrisy (sp?)" fallacy? Because I have a couple examples for it:

1. Found it on YouTube: Since the US began its existence by trampling over the rights of the native people, it can't logically be against immigrants doing the same thing now. Despite the fact that we realize now how bad that was for the natives and obviously wouldn't want the same thing to happen to us. Also despite the fact that we are not our ancestors and have every right to decide on new stances on issues such as these. (This same vid held the idea of "hereditary immigration status," by which I mean that if your ancestors were immigrants then that makes you "an immigrant" and "not native" - unless you're an American Indian, which the speaker appears to believe never migrated from anywhere.)

2. Your people used to be very warlike, so you can't preach anti-war now. Despite the fact that a person could have realized from history that being warlike is a bad idea. A similar thought, less deceiving, might go Your people used to live on the backs of slaves, so you can't preach against slavery now.

So... is there an existing label for this argument, and/or does it even fall under logical fallacies? Because I was kind of annoyed to find the first example (annoyed enough to make up the second example as a possible argument against a singer I ran across).

Drow Lord: Those sound kind of halfway between Ad Hominem arguments (specifically, circumstantial ad hominem) and Sunk Cost. The concept of assuming no change has taken place sounds pretty familiar, but I can't remember what it's called. Those examples, though, are definitely fallacies, you're right about that.

Incidentally, should the Chewbacca Defense go somewhere on this page?

Lull The Conqueror: I see the Chewbacca Defense as a variant of argumentum ad nauseam (literally, argument to [the point of] nausea)... bascially, you just keep repeating your argument until your opponent gets sick of it and gives up. In a standard ad nauseam argument, your argument may or may not be valid, but you won't acknowledge any opposition; the Chewbacca Defense switches this up in that no counterargument is possible because your argument is so nonsensical that you don't even have to bother contriving reasons to ignore your opponents. I think I'll do a writeup for ad nauseam when I have a little more time, or someone else can do it if they beat me to the punch.

Blork: Removed this example from under Many Questions Fallacy:
  • When Joan of Arc was on trial, she was asked if she was in God's grace. It was a trap, as answering yes would be an act of heresy and answering no would count as a confession of guilt. She got around this by giving a long winded answer that can be summed up as "I hope so," or "I don't know."
The point of the Many Questions Fallacy is that any simple answer you give will imply answers to other questions which may or may not be true. For example using the standard question of "have you stopped beating your wife?", if you have no wife, or have never beaten her then the correct answer is "no". This, however, sounds like an admission that you are still beating her. In the Joan of Arc case, answering no would have seriously damaged her position while an answer of yes would require her to know god's will, which would have been heresy in the minds of her accusers. Both of these are valid inferences (provided you accept all the assumptions needed to get this far), meaning that this is a case of "damned if you do, damned if you don't" rather than an example of this fallacy.

Sikon: Pulled:
  • The postscript side, of course, is that them there "very smart" guys are a bunch of elitists, who don't know nothing about how us ordinary good Americans feel. Thank god I don't listen to smart people and just go with what my gut tells me to be true.

Not only is that a rant, but not everyone on this wiki is from the Default Country.

Malicious Illusion: I added a bit after the "Support our Troops!" example under Sunk Cost. I'm not sure if I should have removed it entirely (It's a poor example, and it sounds like someone's got a political drum to beat)... but I also know "sunk cost" no longer applies when there's a cost for trying to cut ties, which makes my addition topical, if kinda nattery. If that was a bad idea, I'll just remove both. Or someone else can do it.

Madrugada: Sunk Cost can still apply when there's a cost to end as well as too continue, if the cost to end is less than the cost to continue. If I have a gym membership that costs me $600.00 for a year and has ten months to run, and it has a $250 cancellation fee, keeping it even though I never go because of the cancellation fee is Sunk Costs: I'm making the decision based on the fact that I've already spent money, even though it would cost me less to cancel than it would to continue.

Lull The Conqueror: Cut:

  • Eh, no. Their point is how unlikely 'random chance evolution' is and therefore scientifically implausible. This is not definitive proof but is a very valid point nonetheless.

On account of its being a demonstration of the very fallacy it seeks to deny. Maybe we should just cut all the Real Life political/religious examples and stick to fiction?

Kriegsmesser: What about the Double Negative Fallacy (subset of False Dilemma), and Partial Incorrectness?

Double Negative Fallacy: (You're wrong, so I must be right.)
A: The sky is always blue.
B: The sky is never blue.
*proof that the sky is currently blue*
A: The sky is blue, it must always be blue.

Or, a more current example.
D: The solution is to give them cake.
R: The solution is to bomb the fuck out of everything.
R: Giving them cake failed, thus, we must bomb the fuck out of them.

Partial Incorrectness: (You got one thing wrong, so everything was wrong.)
A: George Washington was a Russian Male.
B: Hitler was originally British, not Russian. You're wrong about his nationality, you must be wrong about his gender. Thus, Hitler was a woman.

Pro-Mole: Despite the fact you exchanged George Washington with Hitler for no visible reason(except maybe Godwin's Law)... Double Negative is False Dillema (except not in form of a single statement), or at least "quacks like one". Partial Incorrectness seems like a variant of Ad Hominen.

Blork: Removed excessively large image:

furbearingbrick: Sorry, that was me. T.T
ObadiahtheSlim: The Appeal to Ignorance seems to have gotten a bit derailed so I cleaned it up a bit. I'm sorry but the existence of Loch Ness, UF Os, etc are all testable claims. The existence/nonexistence of God is not testable and therefore not in the same boat.

  • Actually, that is true. You can't "rationalize" God. It goes beyond normal human logic. You can't "understand" it, you simply have to believe in it. That's what faith is all about.

And I thought we were cleaning up this page according to the Rule of Cautious Editing Judgment...

So, we were cleaning up political flamebait. Good. I like flamebait clean-up. It's a noble thing. Now this is religious flamebait. I am being tempted to... know what? Damned it be! This is a form of special pleading, in which you claim your opponent does not understand the nature of your argument, and thus you are right. It is not necessarily true, though.

And, specially, this is supposed to be a "Begging the Question" example. I'm trying to come up with a neutral example, that won't attract faith apologists. Thanks for listening the moley rant.

...Well, I tried.

Pro-Mole: BTW, Special Pleading might find its place here, but I'm not quite sure. It works by adding details to the argument, when those details actually do not apply. Mostly, it's used to create double standards, and thus invalidating further arguments. The Other Wiki explains it beter =>

Zetaseal: Removing this (rather inaccurate) flamebait (we're talking civil rights, here, kids, and marriage is not always religious):

  • This Troper has seen this argument used in relation to gay marriage and Proposition 8 in California. There's something strange about putting human rights up to popular vote.
  • An utilitarian might feel that this argument is justified. Also you're begging the question that humanity have inherent rights, and that a particular religious ceremony is one of them.

CapnAndy: Cut this from the Left Behind example, which is wrong through and through and needs no discussion, but I wanted to save it because it's so funny. For bonus points, count the fallacies!

  • truth in television, we trust English majors to give us accurate reports on scientific discoveries and actors to tell us about international politics. The arbitrary substitutes highlight the absurdity. Plus, the president of Romania turns out to be the Anti-Christ and has supernatural powers of persuasion. Its a case of charisma trumps intelligence.

forthur: Removed "evolutionary fact" from the list after "Appeal to Technological Paranoia", as it is neither technological (which is the point of the appeal) nor has contributed directly to human well-being (which is implied in the list). Of course the associated sciences like geology and genetics do have improved human life (either directly or indirectly), but they don't depend on evolution; it's the other way around.

Blork: An understanding of evolution has definitely led to improvements in human life, to give just one example it's really useful to know about bacteria evolving to become resistant to antibiotics so you can respond to this. I'm not sure "Appeal to Technological Paranoia" is technically a logical fallacy though.

Pro-Mole: isn't "Appeal to Technological Paranoia" just a name for a specific use of "Appeal to Tradition"?

SSJ Dk Crew: Sorry, Blork, but bacteria have never evolved to antibiotics. Nothing can evolve in a mere hundred-year period, in response to a completely artificial stimulii created by man. The word you're looking for is "adapting." I hate to say it, and I know it's going to sound petty, but Artistic License - Biology.

Honore DB: The "adapting vs. evolving" distinction you're referring to was invented by evolution denialists and as far as I know has never been adopted into mainstream usage, so Artistic License - Biology seems a little harsh. And while I'm here, evolutionary algorithms definitely count as technology. Create a bunch of random programs, enforce a selection pressure, and cause them to "mate" and "mutate," and they'll solve your problem for you. I'm a programmer, not a biologist, so this is my firsthand knowledge of the validity and usefulness of the theory.
"*** Isn't it more logical to try to convince your opponent that you are right? You don't have to waste resources keeping him in line and you can add his resources to yours."

The claim is that it is illogical, so the above may be a fallacy of moving the goalpost. Also it begs the question that all opponents will accept the same premises and listen or understand your reasoning using another argument. If that worked we wouldn't need prisons, so is it illogical to enforce an opinion through any thing but logical debate?

  • It is not a logical argument, nor indeed an argument at all. It may be a good idea in a given situation, but that's not what is meant by "logical". The point is "Believe me or I kill you" doesn't make your statement true.
  • The argument need not be rhetoric, nor only be concerned it stating a truth.

There is bread in the store
Bread fits under my coat
It can be carried as such
I am in range of the door
I can carry it past the door

Now I have to choose a course of action, not just a conclusion. The consequences of stealing are also a fact, so is it illogical to point them out?
The punishment for stealing is death
Carrying the bread out the door is considered stealing
The owner will kill those who steal

The owner's decision to administer the punishments themselves may not be arrived at logically, but that doesn't make it illogical to recognize that they will do so.

You do not wish to die
Stealing will result in your death
Do not steal

A premise can be true without that truth being logically derived. Otherwise I could claim that no argument that terriers were dog could be logical because there's no logical reason for dogs to have evolved, natural forces did that. Nor for those dogs to have been bred into terriers, people did that according to their own whims. Yet an argument that notes that some dogs are terriers can be logically formed.

Pro-Mole: Dropped, because it's not a fallacious example:

  • This is also often an argument of Pro-Choicers against outlawing abortion ("Back-alley abortions still happen!").
    • The reasoning behind that argument is more that people who will have abortions anyway will be forced to do so in unsanitary environments, with high risk of fatality.

It actually does make sense! Outlawing abortion will not stop people from having abortion, and will just force them to take the illegal and unsanitary way. Whoever added this commited the Fallacy Fallacy.

  • You might be thinking of arguments such as the legalizing of weed, but those often include arguments that there is no victim, or that it fits within our ethical system that accepts alcohol and tobacco. Essentially these arguments include premises based on the idea that certain drugs aren't wrong or evil and build from there. Try arguing that rape still happens despite all the laws against it, so surprise sex should just be legalized. Otherwise somebody is going to get hurt. The argument is a fallacy towards demonstrating the ethical nature of abortion. There needs to an added premise stating why there is an moral imperative or ethical way of killing a fetus. That people disobey a law to their detriment doesn't mean that the law isn't justified.
    • Hm... I have my definite opinion on the matter, but nevermind. You have a point: this bullet should be back, but I think it should include that bit of clarification about the ethical point of the argument. The way it is, isolated from the actual concern, it makes some sense(specially for pro-choicers...).

Removing a piece about the link between the "western diet" and the "western diseases" (heart disease, stroke, diabetes, etc.) mostly because evidence points to the editor's statement (the western diet does not cause western diseases) being false. The editor claims that the issue is purely a demographic one, and that western diseases are indicative of old age regardless of diet and lifestyle, and the only reason that western diseases appear in new populations is because the people there are living longer due to the influence of western medicine. This argument is false, unfortunately. The introduction of western medicine, usually followed closely by the western diet, does increase the life expectancy of less developed countries when it is introduced, as the editor accurately states; however, it is not that more people are living to old age. Once a person lives to be about 40, they can be reasonably expected to live for a few more decades regardless of their environment, simply because if a person is tough enough to live through their childhood without dying of malnutrition or infectious disease and can survive through their prime (war, childbirth and the other perils of day to day life take many people here), one will generally live to a ripe old age. The advantages of western medicine is not that people live longer, but simply more survive childhood, especially when they are their most vulnerable, in the age cohort of 0-4. If the population of middle aged and elderly people is examined before the introduction of western foods, they will be found to have a level of western diseases that approaches zero; after the introduction of the western diet, the prevalence of these diseases skyrockets. A good reference here would be journalist Michael Pollan, specifically his book In Defense of Food. -Mbessgettios
  • Oddly enough, this idea is not quite as fallacious when dealing with computerized systems. Since nearly all "random" number generators are in fact pseudorandom number generators: their algorithms are selected based on how random they seem. As a result, a coin-flipping computer program that has just come up with a long row of heads actually has a greater than 50% chance of coming up tails on the next one - the exact chance depends on the algorithm and the number of heads.
    • Mike Rosoft: Er, no. Technically, a pseudorandom number generator is deterministic, so after getting five heads in a row, there's either a 100% or a 0% chance of getting another heads. But if you don't know the exact algorithm of the generator AND its internal state ... you can as well flip a coin. Precisely because the series of outputs of a pseudorandom number gererator is designed to seem random, it should be just as probable to get heads and tails after a series of five heads, and a deviation in either direction is a flaw. (Random number generators are tested using rigorous statistical tests, and not by checking if the output seems visually random.)

Andrew: Thank you for deleting the example instead of nattering up the entry.

the silent speaker: I removed this example from Irrelevant Thesis:
My opponent says that we need to protect the endangered birds on the island.
This would mean getting rid of all the adorable feral kittens on the island.
What kind of people would we be if we put seabirds over cute kittens?
because I'm not sure it's really irrelevant. To me, arguing that: 1) a proposed couse of action has a secondary effect, and taken together the combined effect has a net unfavorable outcome; 2) therefore we should not follow the proposed course of action; is not a fallacy at all but a valid argument. (We can dispute the premises — it may be possible to save the seabirds without disturbing the kittens, or favoring adorably cute kittens may be neither a prospective nor a retroactive indication of greater moral rectitude than favoring seabirds, or the ecological gain may outweigh the moral loss on balance — but those only make the argument untrue, not invalid.)

Madrugada I won't dispute that edit,mainly because I wasn't really happy with the example either. But we do need an example. How's this:
  • The birds on this island are endangered and must be protected.
  • To protect them, my opponent says that we must reduce the feral cat population.
  • Only horrible nasty people could possibly kill cute fuzzy little kitties.

Madrugada again: The Irrelevant Thesis is inserting emotionally-loaded words ("horrible nasty", "kill" instead of "reduce" which may not involve killing at all, and "cute fuzzy, little kittens" instead of "the feral cat population") which changes the argument from one of "what needs to be done?" to "Are we the kind of people who kill cats?"

  • Certain Christians have claimed that homosexuality is "unnatural". This troper is a Christian, and he's fairly certain it's a stupid argument(whether it can ever be verified or not), because humans do a lot of things that aren't natural. Such as, oh, using computers.

Because it seems to be an equivocation of "natural". One group is using the term in the sense of "normal" or preferred order. Like when some argues that a circus is unnatural, they don't usually mean that a bear shouldn't be capable of balancing on a ball, or whatever. They mean that doing so falls outside of their concept of regular, or normal bear behavior. It's not illogical to have a different ideal for, or prototype of humanity. For them it is counterproductive towards the way they think people should behave. It might be illogical if rejecting it somehow contradicted that ideal, but what exactly that is, and how it does it isn't stated. Maybe that can be narmed up over at Usefulnotesonchristianity but it probably isn't going to fit in here. There seems to be a habit of people sometimes competing over "my axiom is better than yours" on this board.

SSJ Dk Crew: If you ever need that explained, I can definitely explain it. There's no logical falicy involved; just a straightforward teaching that lots of people don't like.

Anonymous: It could be something close to Appeal to Nature though.
Martyr Machine:Deleted the following...
  • !!Deduction and Induction
  • Quite possibly the most frequent mistake made by people attempting to create a logical argument is to confuse deductive reasoning with inductive reasoning. Deduction is when you take a chain of observations and follow them to a logical conclusion. Induction is when you take an observation, generalise it, and use that generalisation to make a conclusion. Both deductive and inductive reasoning can be equally wrong, but induction- because it relies on internal logic- is less logically sound in general.
    • Deductive: All crows are black. This bird is black. Therefore, this bird is a crow.
    • Inductive: This bird is black. Thus, all birds are black. Therefore, a crow must be a bird.
    • Deductive: I notice that you have a pack of cigarettes in your pocket. But I notice that you do not have a lighter. I know that you require a lighter to smoke. Therefore, I deduce that you are not a smoker, and possess the pack for another reason.
    • Inductive: I notice that you have a pack of cigarettes in your pocket. But I notice that you do not have a lighter. I have observed that all smokers carry packs of cigarettes in their pockets. Therefore, I induce that you are a smoker, and that you have lost your lighter.

The definitions are misleading, and the examples make no sense. The first example is deductive but invalid. The second example is not only not inductive, but makes no sense. Two completely unrelated conclusions are somehow being derived from a single premise. The third example is not deductively valid, as the truth the premises do not guarantee the truth of the conclusion. In fact, it would be better classed as an inductive argument (and a fairly weak one. Perhaps he just forgot his lighter?) The fourth example is a reasonable illustration of induction.

The definitions themselves are confusing. The word "logic" is used in its own definition, and "sound" has its own meaning in a logical context, and is misused here.
Cut the Fire Emblem example under Appeal to Force:

  • Fire Emblem 10 (Radiant Dawn) takes this one to the extreme. At the end of the game, the army defeats a goddess to reverse her judgment to have humankind (beorc- and laguz-kind, if you will) erased because they have too many wars.

because the army does not so much reverse the judgment as physically prevent the goddess from carrying it out

Anonymous Mc Cartneyfan: <laughing> That's why it is an example of Appeal To Force. The army has no counterargument - their actions support the goddess's argument - but they force her to change her mind by dint of superior firepower (metaphorically speaking). True, if we reinstate it, it'll have to have fewer spoiler bars, but it is a true example!
Madrugada: I undid your edits to the last paragraphs, Martyr Machine, because they really didn't make things any clearer. "Deductive" isn't mentioned or explained anywhere on the page, so throwing it into the mix at the very end doesn't clarify anything. I also restored the parallel construction of the last three examples, since they hinge on points that people who haven't studied logic often find confusing, and it's easier to see the differences if the examples are directly comparable.
Madrugada again: This

"*** Most famously refuted by John Kerry:
How do you ask a man to be the last man to die in Vietnam? How do you ask a man to be the last man to die for a mistake? "

under "Sunk costs" confuses me. How is that a refutation? A refutation of Sunk Cost would be a statement along the lines that "we need to cut our losses and stop now." Asking "How do you ask a man to be the last to die for a mistake?" sounds more like "We can't stop now, we've invested too many lives." If there's more context that turns it around, that needs to be added to the quote.
Zephid: The perfect argument is not true, valid, and sound. "True" and "valid" are redundant in that sentence: a "sound" argument by definition is both of those. And that's only if you think perfect arguments exist in deductive logic only. Or am I Completely Missing the Point?

Madrugada: I don't know if you're missing the point, but the purpose of that section is to explain and demonstrate how "True", "Valid", and "Sound" are used in formal logic, as opposed to in casual conversation to someone who hasn't studied logic (or who isn't familiar with the vocabulary.) The idea that something can be false but valid or true but invalid can be massively confusing. And we haven't even touched the difference between inductive and deductive logic here, so no, I'm not suggesting that only deductive logic can produce a perfect argument.
SSJ Dk Crew: Just saw the quote under the Ad Nazium about the "Chick Tract, which claims abortion is wrong because Hitler killed Jewish babies." This, by itself, is indeed a logical falicy, though that doesn't mean they've drawn a faulty conclusion with their bad logic. It's not wrong to kill babies because somebody else did it, anymore than it's right to rob a liquor store because someone else did it. The reason why it's wrong to kill babies is... Well, they didn't kill you first.

Madrugada: It's there as an example of the fallacy: "Hitler did this therefore it's evil." Whether abortion is wrong or not is open to debate, but saying that it's wrong because the Nazis did it is not a valid argument. If you look at the section on "True, valid, and sound" at the end of the page, you will note that an invalid argument can have a perfectly true conclusion. But questions of ethics and morality, being questions which hinge on subjective beliefs, do not have a provable truth value.

SSJ Dk Crew: That's not entirely accurate either. Things aren't subjective just because people disagree about them. Ethics and morals are among those things.

Madrugada: Things are subjective if they have no objectively provable truth value. Ethics and morals fall into that category: you cannot prove objectively that "this" ethical stand is true, but "that" one is false. You can believe it, but you can't prove it to someone who doesn't believe it.

SSJ Dk Crew: First off, I think we've arrived at at least one agreement, and that is that the example is valid in expressing a logical falicy, regardless of what the results are.

SSJ Dk Crew: However, it is most certainly possible to verify the value of ethics. If a person steals someone else's car, causes them misery, and winds up becoming wasteful and miserable themselves, even if they may get away with their crime initially, then we can say that the act caused more harm than it prevented with the benefit of hindsight, and thus, we have verified that the act was wrong.

SSJ Dk Crew: Justice and Injustice are even easier to verify, since justice is practically quantifiable. It amounts to simply; "each person is entitled to restitution from their fellow man, proportionate to the harm which that man inflicts on them."

SSJ Dk Crew: Even with all these things explained thoroughly, however, many people will simply refuse to believe it for any number of reasons, personal or otherwise. Under the circumstances, I'm willing to group those together with the people who say the sky is not black. The evidence exists, but they either ignore it or deny it, no matter how plain it is. That doesn't make it any less a fact.

Anonymous: Uh, no. You're taking your personal morals and judging everyone else based on those. That's subjective.
Blork: Removed this:
  • Seen in Richard Dawkins' The God Delusion when he argues that Christians are anti-science and evolution. When he mentions the case of Gregor Mendel (the Augustinian Monk who founded the science of genetics), he argues that Mendel wasn't a real Christian, but just pretending to get funding for his researches.
I looked it up, and Mendel is mentioned in one paragraph of the book which states that "Mendel was of course a religious man". The closest it comes to the above claim is to point out that in the 19th century becoming a monk was the easiest way to get funding.

SSJ Dk Crew: I'm sorry, but I just can't leave this up...

"** Also very popular among people who oppose condom distribution. Since condoms don't prevent pregnancy 100% of the time, and since there are certain ST Ds that a condom is ineffective against, it is better to simply take condoms off the table entirely than let people know they are effective most of the time for preventing pregnancy and STD transmission."

This is entirely untrue. Modern and recent studies have determined that there is no conclusive evidence that condoms help to prevent ST Ds of any kind. This is a myth, though still hotly-disputed by many people. It shouldn't be an example here.

Honore DB: And I just put it back again. I had no idea people (I'm assuming with a religiously motivated agenda) were spreading disinformation like this. Condoms do work; Wikipedia doesn't consider this a controversial statement. See

The U.S. Center for Disease Control, in summarizing the findings, says "For persons whose sexual behaviors place them at risk for ST Ds, correct and consistent use of the male latex condom can reduce the risk of STD transmission."

tkdb: While I agree that the statement about condoms not working is false, I don't think it really qualifies as an example of the perfect solution fallacy because the fallacy applies to instances where the best possible solution is dismissed because it isn't perfect. It says right in the fallacy description:
Rejecting a possible solution because there is a better one, or because choosing to use that solution will prevent the use of a better one is not Perfect Solution.
In this case, the best possible solution (if you're looking strictly at avoiding pregnancy and ST Ds) is 100% effective. Furthermore, the issue of effectiveness isn't the basis of the position held by those who oppose condom distribution, but rather is a rhetorical technique used to persuade others to choose abstinence over sex with a condom. The real basis of their position is rooted in moral/relious concerns, not the issue of what's most effective.

Madrugada: They're saying "Condoms aren't perfect, therefore no matter how good they are, they aren't good enough." The Perfect Solution fallacy doesn't require that a perfect solution actually exist to be fallacious. It only requires that a partial solution be completely rejected solely because it's partial.

Realistically, there is no perfect solution to reject condoms in favor of. Total abstinence would be perfect only in a theoretical world where everyone outside of long-term, monogamous relationships would always be completely abstinent, anyone who has an STD is always compleely abstinent, even within a long-term, strictly monogamous relaitionship, there is no way to transmit the diseases commonly called STDs except sexual contact, and no one is ever raped. Since that won't happen (and even if it would, there still exists the fact that some STDs can also be transmitted through non-sexual contact, even that isn't perfect — HIV can be transmitted through body fluid transference during non-sexual contact; herpes by direct skin-to-skin contact with someone with either an active sore or in the asymptomatic viral shedding stage. The argument is still fallacious, even thought the people putting it forward want to believe that abstinence is a "perfect solution".

tkdb: I think you're misunderstanding the perfect solution fallacy. As I quoted above, from the fallacy description on the main page, the perfect solution fallacy is only fallacious if the solution being rejected is in fact the best possible solution. If there is a perfect, or even simply a better solution, the decision is not fallacious. Abstinence prevents pregnancy and spread of disease through sexual contact in 100% of the cases in which it is used; condoms do not. Thus, abstinence is without a doubt the better solution on an individual level, and persuading an individual to choose abstinence using on the argument that condoms aren't 100% effective is perfectly valid. The issue of STD spread through nonsexual contact is completely irrelevant because condoms don't help any more than abstinence (defining abstinence to mean abstinence from all forms of intercourse, not just vaginal) does in that regard. And regardless, abstinence — while not a "perfect" solution to the spread of diseases known as "sexually transmitted diseases" — is still better at preventing disease spread through sexual contact. Your argument that since abstinence is only better in a perfect world where everybody practices it is also specious. If you take two equally sized populations, one that consistently practices abstinence and one that uses condoms with equal consistency, you will have lower rates of unwanted pregnancy and ST Ds in the former population because abstinence is simply more effective. Additionally, your argument against the effectiveness of abstinence is reliant upon the assumption that it is impossible to make enough people in a population use it to be useful in preventing pregnancy and ST Ds. This assumption strikes me as grossly underrepresenting the power of the individual to restrain oneself and the power of a culture to mold a person's behaviour and attitudes. More importantly, it is completely unproven; in fact, I was taught in my sociology and psychology courses  * that unwanted pregnancy and STD rates in cultures that strictly promote abstinence are comparable to those that use a more progressive sex education policy, with heavy promotion of condom use. Trying to mix the two, however, results in mixed messages that lead to reduced rates of both abstinence and condom use. In short, abstinence is of comparable effectiveness to condom use in practice, and in theory has the potential to be far more effective.

Madrugada: On the contrary. You are misinterpreting the fallacy. The "Perfect Solution" fallacy is rejecting a solution offered because it (the one offered) is not perfect. It doesn't have to be the best possible solution, it can be one of many partial solutions. There doesn't have to be a literally "perfect" solution. It is rejected solely because it is not the perfect solution. The only case in which such a rejection is not fallacious is if adopting a partial solution makes it impossible to use other partial solutions as well, or prevents a better solution from being used. Condom distribution doesn't meet either of those criteria — giving out condoms doesn't make other means impossible, nor does better solutions from being used on an individual basis.

Arima Reiji: Interesting point. One of the key arguments those who are against condom distribution and sex education bring up is that if you distribute condoms or even broach the subject of sex, it will cause people to have sex. Sometimes they're relegated to being insinuations, but they're almost always there. But I don't think it holds water to say that if someone knows the risks of unprotected sex and how to protect themselves (which is the backbone of almost all sex education, not "teaching kids how to have sex") and has a condom available, they will perforce immediately go have sex. (For starters, first they would have to find a willing partner.)

Put more simply, having a condom does not compel someone to go use it. Condom distribution does not preclude the "perfect solution" of abstinence. Indulging in a little reductio ad absurdum, if that were true, you could throw them at nuns to make them give up their vows.

tkdb: Perhaps it would be better to move this from perfect solution fallacy to false dilemma. I can see now how it's a false dilemma, but I'm still pretty sure it doesn't fit under perfect solution fallacy. Like it says in the fallacy description, "Rejecting a possible solution because there is a better one, or because choosing to use that solution will prevent the use of a better one is not Perfect Solution." Whether abstinence is actually a better solution or not can be debated, but the fact is when it comes to determining the use of the perfect solution fallacy the truthfulness of the premises is irrelevant, only the reasoning used to reach the conclusion from the premises. The argument isn't "[P1] condoms don't work 100% of the time, therefore [C] we may as well not use them" (which would be perfect solution fallacy), but rather "[P1] condoms aren't as effective as abstinence, and [P2] availability of condoms discourages abstinence, therefore [C] we should restrict condom availability to promote the most effective solution" (which would be false dilemma if the second premise is false, but is certainly not perfect solution fallacy). The argument may not be sound, but it is valid, and an argument relying on perfect solution fallacy is never valid.

Madrugada: The people who are saying that you can only advocate one way of preventing STDs and preganancy are certainly indulging in False Dichotomy. That may be the best solution, since we disagree fundamentally on Perfect Solution. I'll rewrite the example and move it.

Arima Reiji: I'm not inclined to fight over the issue — but for what it's worth, I think it's both. It's False Dilemma / Dichotomy, because it's based on the false premise that condom availability precludes abstinence. But it's much more exemplary of Perfect Solution, as this very discussion shows.

Claiming that abstinence is logically "better" than condoms due to only one factor (the risk of STDs and pregnancy) is like claiming that refusing to drive a car is logically "better" than wearing a seat belt due to only one factor (the risk of dying in a car wreck). Either would be true if you were making the decision without considering any other factors, but logic does not exist in a vacuum. (Unless you're a philosophical dust mite.)

"Perfect" in only one aspect of a complex decision does not mean something is inherently "better," much less "best". Many, if not most, people see the benefits of a healthy sexual relationship (which extend far beyond momentary pleasure) as outweighing that single aspect. Claiming that none of the benefits matter because it's immoral would be a religious argument, not a logical one.

tkdb: The fact of whether abstinence really is the better solution is irrelevant to the matter at hand, though, because the perfect solution fallacy only applies to the validity of the argument, not the truthfulness of the premises. Because the argument is based on the premise that there is, in fact, a better solution (whether or not that premise happens to be true), it is not a perfect solution fallacy. You can still refute the argument by proving that abstinence is not, in fact, the better solution, but that still doesn't mean that the argument uses the perfect solution fallacy. Perfect solution fallacy is not the erroneous belief that a given solution is perfect; it's the erroneous line of reasoning that leads one to reject an imperfect solution solely because it is imperfect, even if no better alternative is available.

Arima Reiji: The wording of the definition of perfect solution fallacy On This Very Wiki contradicts that already, but clicking through to The Other Wiki link makes matters much clearer. In fact, it even makes the point that perfect solution fallacy is a subcategory of false dilemma.

Pro-Mole: Isn't Circular Reasoning something different, or even a derivative, from Begging the Question? As far as I know, CR is when you beg the question, and then uses that same argument to prove the reverse, creating some sort of "deadlock of truthness". Thus...

B is assumed true
A is true due to B
And B is true due to A

And so you don't have any actual truth, since B is proven true due to A's truth, and A is also proven true due to B's truth, and so on... Or, as I've seen Creationists say...

Scientists determine the age of fossils depending on the age of the geological layer they're found
Scientists determine the age of geological layers depending on the age of the fossils found there

...Which is, by the way, a completely untrue "Strawman". But that's not the point; Circular Reasons is not Begging the Question(or, maybe, Begging the Question is not Circular Reasoning), is it?

Madrugada: You're right, Circular Reasoning is recursive Begging The Question. I'll change that.
Madrugada: I'm questioning whether Magical Thinking and Apophenia really belong here. They are illogical thinking, but they aren't really logical fallacies themselves (Magical Thinking is a result of Post Hoc Ergo Propter Hoc. Apophenia isn't based in logic at all.) What do others think?

Pro-Mole Apophenia is probably some form of the Sharpshooter Fallacy. In short, it is identifying patterns where there's none, right? So, isn't that like bending the evidence (non-existant, in this case) to fit the premise? It isn't a logical fallacy per se, but narrowly correlated, I must say.

calronmoonflower, Magical Thinking could be moved under Post Hoc Ergo Propter Hoc as example of the fallacy in action. Apophenia could be considered a fallacy, however, the fallacy itself would likely have a proper name and Apophenia would simply be an example.

calronmoonflower: I've updated the Pastafarian example to reflect how it is used.

Madrugada: I redeleted this:
** If you are a virgin taking online personality tests, you will inevitably run into a question along the lines of "what kind of people do you have sex with?"
because it is not an example of Many Questions. It's an assumption, based on a statistical probability: that most people taking the survey will have had sex. It's there for everyone, not just virgins, and it's not an attempt to make them admit to something. Those same surveys probably ask "Do you own or rent your home?" as well, which is not a Many Questions fallacy aimed at people who still live with their parents ( and therefor neither own nor rent.) Bad assumptions are not necessarily logical fallacies.
  • Majutsukai: Doesn't matter to me enough to contest it a second time.

Madrugada: {Void}} here are more links to the comets/paper example under Moving the Goalposts:
  • Louis Frank's account of finding them and the reception his interpretation paper received: here. There is also a link at the bottom of that page to the 10 comments that were published in Geophysical Research Letters and Frank's responses to them.
  • Article in the Boston Globe (Requires free registration to see the whole article)
  • The original site I found this on.

What's your evidence that this is in error?

Wraith_Magus: After writing out a reason, it kind of grew, so I figure it would be better to post it as a discussion, instead... The original:
  • The debate over a recent ballot measure in Oregon that paid for children's health care by increasing the cigarette tax is an illustration of the Association fallacy. The argument of many of the measure's supporters was essentially, "Big Tobacco opposes this measure. Big Tobacco is evil. Therefore, if you oppose this measure you are as evil as Big Tobacco." This association fallacy was added to the general "you fail logic forever" quality of the measure itself; the measure relied on people continuing to damage their health by smoking in order to fund children's healthcare. Fortunately, not everyone in Oregon failed logic and the measure didn't pass.
I took off the last few sentences (starting at "This association fallacy...") with the political Take That! jab in the example... Ironically enough, in taking some supporters of a bill who fail logic and making the leap to say that anything else in the bill must have no merit (without presenting any supporting evidence this is the case), the troper makes a Tu Quoque fallacy. Often times, cigarette taxes (or alcohol or other controversial products) are added onto bills not because "they want to support healthcare with smoking", but because raising taxes directly is often controversial, but putting taxes on "sinful" actions will spark less taxpayer ire. Although this troper has no proof of it, there is a likelyhood the money generated by the tax would not be earmarked solely for the healthcare of children, anyway, meaning the cigarette money would pay for every government service, and the health care would be paid for in part by every other tax. These are really two seperate initiatives: a plan to provide more health care for children, and a plan to generate more money because they want to add to the budget without subtracting anything else from it. It is not a grand comprehensive strategy to turn unhealthy activities into healthcare, but a coincidental political tactic to try to make the bill more likely to pass.

Why is all of this in syllogisms rather than predicate logic?

Madrugada: Because predicate logic notation is incomprehensible to people who have not studied it. Syllogisms are understandable even by people who have never formally studied logic. This page isn't for people who already know logic; it's for the people who haven't studied it. And it''s much easier to see where the error is with statements like "All dogs are mammals" "All cats are mammals" "Therefore all dogs are cats" than "D ∀ M and C ∀ M, therefore D ∀ C."

Vert: Hey there Madrugada, just to clarify things on the appeal to authority thing, since I think we both agree, but have some sort of misunderstanding. When I say that citing an expert is a logical fallacy, I mean that it holds no logical value in itself. The argument may very well be valid, but then there would be no necessity to actually reference the source of the argument, i.e., if it's right, it's right no matter who said it.

So simply citing an expert and saying that this is valid logic argument is, as far as I understand it, wrong. It may not be a fallacy always, as you point out, but only when the argument itself is correct, irrespectively of who cited it. Thus, from a logical stand point, it doesn't matter whether or not the person is an expert on a subject.

Better yet, let me put it this way: for a argument to valid from a logical point of view, it must be valid (from it's premises) for all cases. The text says that the only premise in this case is that the authority we are using is an expert; however, as I've pointed out, an expert (even The Expert on something) can present a logically false argument (say, Einstein saying that A causes B, so not A happening means not B must also happen), so obviously this is Not Valid for all cases within our premises.

If we amend our argument to add that the expert himself presents a logical argument, fine, we avoid making the mistake. Otherwise, this is fallacy in a general sense (that is, it is not logically valid for all cases, but is presented as such). Agreed?

Madrugada: Hmmm. I see what you're saying, but the fallacy involved in appeal to Authority is that the truth value of the argument itself isn't taken into account — the "authority" is all that is invoked. Basically, if it isn't "Famous Guy said it, it must be true," it isn't an Appeal to Authority.

Here's the definition I'm using: Appeal to Authority. Note the alternate names: Irrelevant Authority, Inappropriate Authority, Questionable Authority.

Here's the nutshell version:

"What distinguishes a fallacious Appeal to Authority from a good Appeal to Authority is that the argument meets the six conditions discussed above.
  • The person has sufficient expertise in the subject matter in question.
  • The claim being made by the person is within her area(s) of expertise.
  • There is an adequate degree of agreement among the other experts in the subject in question.
  • The person in question is not significantly biased.
  • The area of expertise is a legitimate area or discipline.
  • The authority in question must be identified.

That's where I'm coming from. Even experts can be wrong, which is why I took out the "If Einstein had said we could go faster-than-light, citing him as an authority would be fallacious." He'd still be a legitimate authority, he'd just be a legitimate authority who was wrong.

Vert: Well, to be honest, I can agree with that appeal to authority that satisfies those conditions can valid in a 'informal way' (and, indeed, I use this on a day-to-day basis), but I still think it's not correct in a strict, logical view point (which requires absolute accuracy in your argument). I guess it's ok to leave things as they are and I won't press my point, specially since I don't want to get into a edit war. =]

Madrugada: I won't edit war with you. It appears that we're running into a difference in what we were taught constitutes a fallacy. My instructors taught that fallacies affect validity, and that truth value was irrelevant to fallaciousness — that is, a fallacious argument could be true, and a false argument could be completely non-fallacious. Neither are sound, but truth and validity are two different things.

Vert: Oh, I understand now. It's fine then, leave it the way it is.
Insanity Prelude: Anything we missed?

Madrugada: I don't think so. Some different names, but nothing we've missed completely.

Madrugada: Cut this from Ad Hitlerum, since it's being disputed. I haven't seen the movie — those who have care to comment one way or the other?
** The film Expelled is basically 90 minutes of Reductio ad Nazium calling evolutionists Nazis.
  • Actually, the movie focuses on the issue of censorship of ideas within the mainstream scientific community that question evolution (intelligent design or not). And while it did suggest that the theory of evolution contributed to ideas that fueled the Holocaust, it never calls evolutionist Nazis.

Bluestar28: * This clip directly from the movie: (Particularly starting at :45) explicitly denies that Darwinist are Nazis. The only thing the movie claims is that there was a connection between the ideas of Darwinism and the ideas that fueled the holocaust. True or not is another discussion entirely, it simply does not meet the conditions of the trope.

Madrugada Cool. If it's not an example it's not an example.

Pro-Mole: Discussing this...

  • It should be noted that random number generators in video games are actually more prone to causing the the Gambler's Fallacy to come true. Random numbers in computers are created by repeatedly dividing out a seed number by a cycle of values to produce long decimal values, so the results tend to come in patterns. If your sword has a 1 in 20 chance of getting a critical hit, it is far more likely that you will actually get one critical hit every 20 times than if you were using dice.

Not if the random number generator is well programmed, and most of them these days are. A very simple technique to avoid too much pseudo-randomness is to vary the seed by randomizing it or using the current timestamp as a seed. This last one means that you can't be sure what number will come out, unless you repeat the same action at the exact same time(or figure out the algorithm and repeat the action in the exact milisecond when the number will repeat itself).

Madrugada: I think we've already had to clean out some natter about how random-number generators work. How about simply replacing the examples with something along the lines of "A computer random-number generator can be anywhere from very good to very bad at producing truly random numbers, depending on the algorithm and the way the seed number is determined." Would that cover it?

korax1214: As well as the common linguistic error of using "decimal" for "fractional" when it actually means "by tens" (which in turns comes from the lazy habit of dropping the actual noun from a noun-phrase and using just the adjective, in this case "decimal" for "decimal fraction"), the example is factually wrong; all quasi-random-number generators I've seen use multiplication, not division (except in the final step of scaling the result to the range 01), deliberately allowing the multiplication to overflow and depending on the outcome of this being unpredictable in practice. (Of course there are also hardware RN Gs for when truly random results are needed; these use noise sources or the like.) If the example is to stand, instead of giving details of exactly how the RNG works (which are always going to be wrong for at least one implementation) there should be substituted something about how calculated "random" numbers cannot by their nature be truly random, although they can be chaotic, which is close enough to random for most practical purposes.
Madrugada: I cut this:

** Kent Hovind is a Young-Earth creationist who's offering 250,000 American dollars to anyone who can prove the theory of evolution. He also wants this definition to show how other things happened without God, like how the universe came into being.

from the Moving The Goalposts section, since that fallacy only occurs when terms are set, an argument that meets those terms is offered, and then the terms are changed. That doesn't sound like the case here — he's simply set the bar ridiculously high in the first place. The difference between what he says in the headline and what he says in the detailed requirements to collect isn't moving the goalposts — headlines regularly simplify and omit details. However, it may be a different fallacy, but I'm not sure which one — Lobbing the Burden of Proof, perhaps?

<Dab> Madrugada, your interpretation of "Appeal To Authority" is a clear case of You Fail Logic Forever in itself. Just because Failpedia thinks so doesn't make it right (THERE! you committed this fallacy again) Stop doing that. Argument Ad Baculum.

Madrugada I don't think that Appeal To Authority works that way because Wikipedia says so. In fact, in the section you edited, you'll note that Wikipedia isn't the page cited. I think that appeal to authority (and all of the fallacies on this page) work that way because that's the way my logic professor taught. Fallacies affect validity, not truth. An argument can be fallacious and still be true, or false and still valid.
  • <Dab> You may or may not have noticed that I'm very well aware of the difference. What you call "validity" is nothing less than the truth value of X in a statement such as X:(A /\ B -> C) where A and B are premises and C is a conclusion, while X is the statement. In this form, premises, conclusions, and the whole statement itself all can be true or false invariable from each other. A fallacious argument X:(A /\ B -> C) is not true, because, well, it is the fallacy. Premise A may be right, premise B may be right. Conclusion C may be right. But if the reasoning of X is fallacious, the truth of C (based on the premise of A and B) cannot be asserted with the logical argument X and the premise of A and B. I repeat, C alone may still be true. Conversely, asserting that C is not true because C happens to be the conclusion of the fallacious argument X, is the core of the fallacy fallacy. But back on topic: There is no number of "qualifiers" for the "expert" in question that makes the Argument from Authority any less fallacious and I find that statement to the contrary, frankly, offensive. God personally asserting something doesn't make it true. Only it being true makes it true. The site you posted simply has it wrong, and with capital Wrongness. An appeal to authority is never a valid logical argument, that's why it's called a fallacy.

Formal Logic Example A is "This person is an expert" and B is the statement in question:
  1. Assume A.(tt)
  2. Assume A -> B. (ff)
  3. Hence: B. (ff)
The fallacy is assuming that step 2 is true, namely assuming that "The expert says so, so it must be true" when this is really no valid proposition, and doing so is the argument from authority fallacy.

<Dab> There is now the problem that the examples also fail logic because they address the wrong definition of the fallacy. I think they can be rewritten so they describe the problem accurately. Or they can be erased. Opinions? Volunteers for rewriting?

Madrugada: You're the one who changed it so that it's wrong.
  • <Dab> I edited the examples. Review at your leisure.

<Dab> In other news, I believe the fallacy fallacy should be moved to the beginning of the page due to importance. Also, there's a shit ton of examples in the fallacy fallacy section that simply... aren't. But instead are "Logic Does Not Work That Way" sort of errors.

<Dab> I vaguely remember an "argument from lack of imagination" fallacy or somesuch which goes something like this:
  1. Animals Exist
  2. I cannot imagine a naturalistic way for Animals to come into existence
  3. Hence, Animals came into existence due to supernatural causes

Doesn't only apply to the supernatural of course but that's one of the most obvious usages. Failpedia seems to cite it as a variation of argument from ignorance (which goes "Its not proven false, hence it must be true") Does anyone have more so it'd be worth adding?

Oooh I thought of a way to express this in formal logic:
  1. Assume A. (tt)
  2. Assume B -> A. (tt)
  3. Hence: B. (ff)
The fallacy is of course in step 3, because you can't deduce B from (A /\ (B->A))
  • Begging the question: "Proving" that something is true by taking your conclusion as one of your premises, usually done implicitly rather than explicitly (few people are fooled by having your conclusion as your only premise, such as: "Joe is mad at Jill, therefore Joe is mad at Jill."). Such arguments are valid, and sound if the premises are true, but utterly vacuous. Be aware though, that "Begging the question" has come to mean "leading inevitably to the question" in popular use and for this reason, this fallacy is often referred to by its Latin name, petitio principii in more formal settings.
    Alice says she didn't kill Bob.
    Alice is honest.
    Thus, Alice didn't kill Bob (because she says she didn't.)

This is actually not an example of question-begging at all. The conclusion, "Alice didn't kill Bob," is not assumed in the statements "Alice says she didn't kill Bob," and "Alice is honest." I have therefore changed the example.
<Petranca> This troper is having trouble classifying a fallacy. For an illustration: if the tobacco lobby said "You say there is a link between smoking and cancer, therefore you desire that smokers develop cancer." (This troper hasn't heard of even the tobacco lobby showing that much chutzpah, but, in the immortal words of Archy The Cockroach, "similar absurdities have lodged themselves in the human cerebrum"). This troper has temporarily dubbed that sort of argument "credere velle est (To believe is to wish)" pending its true classification.

Honore DB: If you wanted to sound technical without using Latin, you could call it equivocating normative and descriptive speech. Or proscriptive and descriptive. There definitely should be a name for it.

Madrugada: Moved this from the main page:
  • I think we need a new one: The Diametric Fallacy!
If one outcome is bad, the other must be good. For example, if I cease smashing my hand with a hammer, I will have a broken hand. Therefore, if I continue to smash my hand with a hammer, the outcome will be good."
The main page is not the place to discuss adding something.