All About Logical Fallacies

I have a very low tolerance of logical fallacies because I embrace logic and truth.

If you use any of the logical fallacies below, you are embracing deception and lies. Pay attention to this and rid yourself of all logical fallacies.

Argumentum ad hominem. This logical fallacy connects the argument to the man. You attack the man, prove he is a worthless scumbag, a deceptive clown, and then the argument is proven false.

The problem with this is that it doesn’t work. If it did work, all I have to do is get a worthless scumbag to speak the truth, and thus invalidate it.


Illogical Ian: You’re wrong because you’re a stupid, racist, religious, rich, capitalist pig!

Logical Leo: So, you’re saying that whatever I say is wrong because I’m a stupid, racist, rich, capitalist pig?

Illogical Ian: Of course, you idiot!

Logical Leo: So whatever I say is a lie and completely false?

Illogical Ian: Of course, you racist pig!

Logical Leo: Very well, then I wholeheartedly declare that you, Illogical Ian, are a very nice person, who is logical, trustworthy, and someone all men should worship and emulate.

Illogical Ian: Thanks, but no thanks, you retarded imbecile.

Logical Leo: I also declare, the earth revolves around the sun, scientific investigation is a good way to investigate claims about nature, and that I owe you twenty dollars.

Illogical Ian: I don’t get it, why are you talking so kindly about me and using logic all of a sudden?

Logical Leo: Didn’t you just declare that everything I said was illogical because of who I am?

Illogical Ian: Wait a minute… I see what you did there…

Argumentum ad populum: This common logical fallacy relies on the fact that “everybody” believes it or accepts it as true, therefore it is true. It can also be used to replace specific authorities with a more collective “all scientists”, “all politicians”, “all reasonable people” claim.

Illogical Ian: I know its true, because everyone says its true!

Logical Leo: I don’t think it’s true. So since everyone doesn’t say it’s true, it must not be true, then?

Illogical Ian: Well, most reasonable people say its true!

Logical Leo: It wasn’t too long ago that most reasonable people though that slavery wasn’t a terrible idea.

Illogical Ian: That’s a different thing man…

Logical Leo: And not too long ago, the vast majority of the American public supported the invasion of Iraq.

Illogical Ian: Hold on…

Logical Leo: I can give you plenty of examples where public opinion, or the opinion of a large group of any people, turned out to be wrong. In fact, I can only say with certainty that no one knows everything, or really, anything. At some point, some part of their understanding will be proven wrong. Hopefully, at that point, they will embrace the new understanding and logic. Either that, or leave themselves behind on the dustbin of history.

Affirming the consequent. This is a logical fallacy that everyone seems to make regarding scientific theories. It works like this.

“If P, then Q.” That’s the theory.

“Q.” That means, the predicted results are observed.

“Therefore, P.” This is the fallacy. Just because a theory predicts a result and that result is observed, doesn’t mean the theory is true. There are, after all, a gazillion other theories that could explain the same result, including the simple theory, “God did it.”

If you want to go from “Q” to “P”, then you have to start with “If not P, then not Q.” In other words, prove that the only explanation for Q would be P, since if P is not true, then Q cannot happen.

This is an extraordinarily impossible thing to prove.

Illogical Ian: If it’s raining, then the ground is wet.

Logical Leo: Sounds right.

Illogical Ian: The ground is wet.

Logical Leo: Yes, but I see where you are going and…

Illogical Ian: Well, it must be raining, then!

Logical Leo: Ian, have you heard of affirming the…

Illogical Ian: Grab your umbrella, dude! Hey, why aren’t there any clouds in the sky right now? Who turned the sprinklers on?

Denying the antecedent. This is another fallacy that is just as bad as “affirming the consequent”. It looks like this:

“If P then Q.”

“Not P.”

“Therefore, not Q.”

In plain English, “If it’s raining, the ground will be wet.” “It’s not raining.” ‘Therefore, the ground is not wet.”

Logical Leo: Ian, right now might not be the best time for a picnic on the grass.

Illogical Ian: Why not? It’s not raining, so the ground is dry!

Logical Leo: I regret to inform you that…

Illogical Ian: Sandwich?

Logical Leo: … yeah. Enjoy your picnic in the sprinklers, bud.

Changing definitions. This one is harder to catch, because it relies on a subtle trick of language. See, each word can mean more than one thing. And if you reuse the same word, it looks like you are using the same meaning. But this is often not the case.

When logically reasoning, you really have to treat words as symbols. Try to identify what each symbol represents, and be very consistent. If it’s apparent that the speaker is switching definitions, then point that out.

False dilemma. In this logical fallacy, only a few options are presented as possibilities, when in fact there are more.

It’s ok to say “Either X is A or not A.” It is not ok to say, “Either X is A or B” unless you can prove that both A infers not B and B infers not A.

Confusion, or the Chewbacca Defense. This logical fallacy attempts to win the argument by confusing the audience. Unneeded facts and unnecessary correlations are drawn. This is a favorite of conspiracy theorists, since they bring in a ton of information and try to draw a logical conclusion by sheer volume.

To defeat this fallacy, point out what the attacker is doing and get back to the core of the argument. Often, restating the problem in simpler terms, identifying the real points of interest and conflict, will disarm the opponent.

See for more logical fallacies.

6 Responses to “All About Logical Fallacies”

  1. Logical Fallacies, Religion, and Hypocrisy Says:

    […] the guy kindly instructs the reader on All About Logical Fallacies. In particular he preaches about the so called … Argumentum ad populum: This common logical […]

  2. Argumentum ad Populum and Religion « Federal Way Conservative Says:

    […] difference between that and argumentum ad populum, a particularly common logical fallacy, is that one is placing your entire faculty and reason in the hands of some group of people, while […]

  3. Andrew Han Says:

    I find it strange that you would mention logical fallacies given your conservative temperament; a quick google search will clearly reveal that the Left places a far greater emphasis on the formal study of logic than does the Right.

    This is clearly visible through conservatives’ statistically lower average intelligent quotients and smaller presence in academia.


    Ad hominem – “Influential scientists like Carl Sagan agree that global warming is a manmade phenomena with serious potential effects for human society, and have provided huge amounts of scientific data in support. However, Carl Sagan is an atheist and immoral. Therefore, global warming is clearly a hoax.”

    Appeal to popularity – “Liberals have argued that is is inherently illogical to run a government based on religious faith, which is openly illogical by definition (look up “faith” in a dictionary). However, more than 70% of Americans today are Christians, and our founding fathers were Christians (the latter if false, BTW). Therefore, we should make laws based on Christianity.”

    Affirming the consequent – “If God made miracles and I prayed for him to save me, I would be saved. Several dozen people died in that massacre the other day, but I prayed and I survived a severe gunshot wound. Therefore, God must have answered my prayers (never mind the several other people that died, and never mind modern medical science)!”

    Affirming the antecedent – “If Obama’s birth was captured on video, we would be certain that he was born in the United States. However, we do not have his birth on video. Therefore, he was born in Kenya.”

    Changing definitions – “Evolution is just a theory, as Darwin himself and scientists today say. Therefore, it is just a guess.”

    False dilemma – “You’re either with us, or you’re with the terrorists.”

    Chewbacca defense – “Um, you see…the bailout is all about job creation. It’s good for Americans, because…it will help create lots of jobs. And housing markerts. I know this because I am a hockey mom. Did I mention that I can see Russia from Alaska? I therefore am good at foreign policy. So that’s why the bailout is good for the working and middle class.”

    Every single one of these examples I have heard, numerous times, from your conservative friends.

    • Jonathan Gardner Says:

      “This is clearly visible through conservatives’ statistically lower average intelligent quotients and smaller presence in academia.” You mean this study? Yeah, good job there. You just got scammed.

      You are the worst sort of imbecile. You think you are smart, but are really not.

      Your subsequent statements are just as vacuous as your first.

  4. Juan Carlos Rodriguez Says:

    Hello Mr. Gardner,

    I think that Mr. Han was trying to vouch for is the fact that the left has been characterized by a stronger tendency to separate religion from the state, therefore making judgments that appeal more to a common rationale than to a specific religion. A religion would try to dictate how closely should it intervene, or otherwise guide, the decisions a government makes upon their subjects, based off its doctrine. This, while not completely unacceptable, would coerce other individuals who don’t necessarily agree with religious-influenced policies to act or behave in a manner that may be inconsistent with their own beliefs. Furthermore, this state-religion interaction would cause uncertainty about how democratic policies and policing are, and how akin these two elements of governance would be to the governed people.

    • Jonathan Gardner Says:

      Juan, your thoughtful response exposes why religions need to interact with government. Let me explain.

      You are absolutely right that having one religion dominate a government is a sure road to oppression. Other religions don’t accept all of the tenets of other religions (else why are there separate religions?)

      Ideally, we’d like government to represent all the common elements of religion. For instance, almost all religions have a teaching that murder is wrong, and even go one step further and claim a religious duty to execute the murderer. That is probably something we should encode into law. On the other hand, my religion, the Church of Jesus Christ of Latter-day Saints, teaches that alcohol, coffee, tea and tobacco are not for human consumption, while other religions teach that such substances are not particularly bad and sometimes are actually religiously proscribed (such as wine served as part of the eucharist.)

      How do we separate out which teachings we should encode into law, and which we should not? The answer is to have *all* of the religions come to government and meet at that place as a middle ground to discuss what they feel should be the law and what they feel should not. If a religion feels oppressed, they should come to government and say so. If a religion feels something should be a law, they should come to the same place to say so.

      In this way, government achieves a role as a clearinghouse where we can come together to create a unifying, shared morality and common religion that we all feel comfortable ascribing too. Government can be a glue that binds Catholics, Mormons, Baptists, Muslims, Jews, Hindus and Buddhists into a cohesive and ordered society, where we all learn how to get along and tolerate and even embrace each other.

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