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  • How to Spot a Bad Argument

    Nice little post over on Paul's Tips on common forms of bad arguments. You might want to think about these the next time you end up in a Sandbox tussle.

    http://www.paulstips.com/brainbox/pt...a-bad-argument

  • #2
    Re: How to Spot a Bad Argument

    Originally posted by Mateo
    Nice little post over on Paul's Tips on common forms of bad arguments. You might want to think about these the next time you end up in a Sandbox tussle.

    http://www.paulstips.com/brainbox/pt...a-bad-argument
    Reminds me of a Monty Python sketch.

    DB

    «That looks like a really nice house except for that horrible bathroom.» Donrhos

    | |





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    • #3
      Re: How to Spot a Bad Argument

      Great link! I love analyzing arguments and seeking out fallacies - Wikipedia has fantastic summaries of most fallacies as well.

      Correlation causes causation and straw man are both listed in Mateo's link, and are frequently found in all sorts of discourse - Sandbox and otherwise. One I wish he'd listed is equivocation, in my opinion one of the most common, easily missed, and insidious of all fallacies.
      A policy of freedom for the individual is the only truly progressive policy. -F.A. Hayek

      "$250,000 a year won't get me to Central Park West."

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      • #4
        Re: How to Spot a Bad Argument

        These are called informal fallacies, and are usually taught in a critical thinking class. Too bad it's not a required course. One's got to wonder, along the lines of Aristotle and Plato, whether a democracy can work with a really dumb population.

        These are just a couple of common ones. Here are some other very common ones that I see people making:

        Post Hoc, Ergo Propter Hoc:
        Somewhat similar to correlation implies causation, but not quite. Wikipedia says it's the same thing as affirming the consequent. Whoever wrote that page was wrong. It's similar, but they aren't the same. One commits this fallacy when one infers a causal relation A causes B from the fact that A happens, temporally, prior to B. A occurs before B therefore A is the cause of B.

        Example: "The picture on Jim's old TV set goes out of focus. Jim goes over and strikes the TV soundly on the side and the picture goes back into focus. Jim tells his friend that hitting the TV fixed it."

        Appeal to ignorance:
        One argues that there is no evidence against a claim P, so, therefore, one is entitled to believe that P (or in other versions that P is true). "There's no evidence that UFOs don't exist, so I'm not being irrational in believing that they do."

        Hasty generalization:
        An inductive argument based on too small a sample size. For example, "my friend got food poisoning from burger king last week, therefore, because I don't want food poisoning, I'm never going there again."

        Denying the antecedent:
        Just like affirming the consequent, but going the other way. Example, modified from Mateo's link:
        ""If my business partner was stealing from me, he'd probably buy himself a fancy car. He did not buy a Mercedes, so he's probably isn't stealing from me."

        Slippery slope fallacy:
        This takes the form of a string of if-then statements where the last consequent is soemthing no sane person would endorse or is a very bad thing. It is then concluded that the first antecedent is false or shouldn't be so. Example:
        If we don't stop the Communists in South Vietnam, they'll take over the whole country.

        "If they take over Vietnam, next they'll conquer Laos, Cambodia, and Thailand.

        Once they have Laos, Cambodia, and Thailand - they'll overrun Indonesia and the rest of the Pacific Rim.

        Once they conquer the Pacific Rim, they'll take Japan - and the next thing you know, they'll be off the coast of California!

        [implicit: Communists invading California is unacceptable]

        [explicit] We must stop the Communists in South Vietnam."

        Equivocation:
        When a term in the premises is used to mean different things on seperate occasions. Example:

        "1) It is wrong to kill innocent human beings

        2) Fetuses are innocent human beings

        Therefore, it is wrong to kill fetuses."

        Moral philosopher Mary Anne Warren argues that the phrase 'innocent human beings' in the first premise has a different meaning than the same phrase in the second premise.

        Innocent human being in premise 1 = "conscious of moral choice, but not guilty of committing/choosing an immoral act"

        Innocent human being in premise 2 = "innocent because the fetus is not capable of moral intentions and choices in the first place"

        This example may be contentious, but you get the idea.

        There are many many more. What might be somewhat surprising is that some many informal fallacies are formally valid arguments. By the way Tybalt, I've looked at some of the wiki fallacy pages. Some of them confuse what look like distinct fallacies as the same one. Maybe I'm just nitpicky. But under the logical fallacy or formal fallacy page they list a whole bunch of informal fallacies as common examples. :( No, no, no. Most arguments which are informally fallacious can be put as a formally valid argument. Shame on whoever made that page.

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        • #5
          Re: How to Spot a Bad Argument

          Originally posted by sordavie
          Denying the antecedent:
          Just like affirming the consequent, but going the other way. Example, modified from Mateo's link:
          ""If my business partner was stealing from me, he'd probably buy himself a fancy car. He did not buy a Mercedes, so he's probably isn't stealing from me."
          That one's a perfectly logical argument. In logical terms:

          Given: If A, then B
          Given: Not B
          Therefore: Not A

          Of course, its still entirely possible that you might have your "given"s wrong, but the logic is sound. (ie, do you know if a fancy car is really at the top of your partners wish list, or whether its something else like a House?)

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          • #6
            Re: How to Spot a Bad Argument

            Kerostasis, I'm unsure what you mean when you say it's a perfectly logical argument. Yes it's formally valid. However, in this case, it's also an informal fallacy. As I mentioned in my first post, many informal fallacies are formally valid. If what you mean by perfectly logical amounts to formally valid, then I agree, it's perfectly logical. If perfectly logical is taken to mean something like "should be convincing to any rational person," then no it is not since it contains an informal fallacy. Consider circular argumentation:

            If p then q
            Therefore if p then q.

            This is a formally valid argument. That is, it is not possible for the conclusion to be false while the premises true. However, there's an informal fallacy involved here. Informal fallacies have little to do with the logical structure of an argument. That's why they are informal fallacies rather than formal fallacies.

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            • #7
              Re: How to Spot a Bad Argument

              I <3 this thread.
              Beatnik

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              • #8
                Re: How to Spot a Bad Argument

                We've reached nerd factor five, captain!

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                • #9
                  Re: How to Spot a Bad Argument

                  Originally posted by sordavie
                  Appeal to ignorance:
                  One argues that there is no evidence against a claim P, so, therefore, one is entitled to believe that P (or in other versions that P is true). "There's no evidence that UFOs don't exist, so I'm not being .
                  Maybe it is just the example but I find it a weak arguement but it does have merit. Can't really prove something exists without evidence and you also can't disprove it without evidence.

                  On top of that UFOs mean unidentified flying objects. Yes they do it exist. ;)
                  RX-78-2 Gundam EFSF Protoype Close Combat Mobile Suit Armor: Luna Titanium Armament: 2x Beam Sabers, 2x 60mm Head vulcan guns 380mm Hyper bazooka, Beam Rifle, Beam Javelin, Hyper Hammer, Gundam Hammer, shield
                  TG Natural Selection admin. Need anything PM me.
                  7th Infantry FTW!!!!!
                  "Snob? Nah...I consider myself more of a PC Evangelist...converting the heathens to The Way." Prophaniti
                  "Windows is like Pokemon you gotta catch'em all." kenshinsama1

                  [tg-c1]

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                  • #10
                    Re: How to Spot a Bad Argument

                    Originally posted by RGM-79N_GM_CUstom
                    Maybe it is just the example but I find it a weak arguement but it does have merit. Can't really prove something exists without evidence and you also can't disprove it without evidence.

                    On top of that UFOs mean unidentified flying objects. Yes they do it exist. ;)
                    The absence of evidence that UFOs exist is only a necessary condition for rational belief that they do exist. But it is not a sufficient condition, I take it.

                    The term 'UFO' is probably ambiguous. On one hand it is used to refer to any unidentified flying object. :P On the other, it is reserved just for non-earthling spacecraft. :p I meant the latter.

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                    • #11
                      Re: How to Spot a Bad Argument

                      @Sordavie:

                      The way I see it, there's 2 basic ways to put together a formally valid argument that fits the definition of an informal fallacy.

                      A) The argument is true, but offers an irrelevant conclusion, or proves something different from what it was intended to prove.

                      B) The argument would be true if the premises were true, but it's based on faulty premises.

                      Certainly both of these forms are fallacies--but then there is no reason to separately list each normally valid argument that can be marred be these fallcies, and label that as a New and Separate Fallacy is there? They are nothing more than forms of these 2 already listed.

                      So your label of "Denying the Antecedent" is nothing more than a variant of "Faulty premises", and since it doesn't even clearly mention that faulty premises are involved, I consider it a bad label.

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                      • #12
                        Re: How to Spot a Bad Argument

                        Rational belief? Is it not rational to think that there is life beyond this planet and that some of it could be smarter then us. Now I will give you that it is a small chance of some UFOs being ET ships but the chance is there.

                        The term UFO isn't really ambiguous. It is very straight forward it is just that it has come to mean alien spacecraft when it really shouldn't (/end of George Carlin mode)

                        Speaking of him this reminds me of this part in his recent book compairing how the media views the belief that UFOs are alien space crafts and belief in God. It was a pretty good one too. Not only funny but I would be hard pressed to deny that he has a point.
                        RX-78-2 Gundam EFSF Protoype Close Combat Mobile Suit Armor: Luna Titanium Armament: 2x Beam Sabers, 2x 60mm Head vulcan guns 380mm Hyper bazooka, Beam Rifle, Beam Javelin, Hyper Hammer, Gundam Hammer, shield
                        TG Natural Selection admin. Need anything PM me.
                        7th Infantry FTW!!!!!
                        "Snob? Nah...I consider myself more of a PC Evangelist...converting the heathens to The Way." Prophaniti
                        "Windows is like Pokemon you gotta catch'em all." kenshinsama1

                        [tg-c1]

                        Comment


                        • #13
                          Re: How to Spot a Bad Argument

                          Oops I made a mistake in explaining denying the antecedent. That's probably confusing people. It should be:

                          Denying the antecedent:
                          Just like affirming the consequent, but going the other way. Example, modified from Mateo's link:
                          ""If my business partner was stealing from me, he'd probably buy himself a fancy car. He was not stealing from me, so he probably wouldn't buy himself a fancy car."

                          There you go. It's not formally valid, just like affirming the consequent.

                          Sorry about that.

                          Kerostasis, but on your point of not making distinctions between certain informal fallacies, I don't see why we shouldn't. Maybe you have no use for such fine grained distinctions. But that doesn't mean those who study them shouldn't make them or that they aren't there. Circular argumentation doesn't fall in either of your categories. Slippery Slope is another that doesn't fall into either of your categories. (I also take it A is supposed to be "the argument is valid, but offers an irrelevant conclusion, or proves something different from what it was intended to prove" since arguments are not true or false but valid or invalid.) As for your second category, I take it there are many ways a premise can be faulty. Some of these ways are common enough to be given names.

                          For instance, if you take a valid argument that's guilty of false dilemma you've got some premise which does not present the full range of choices. That's one way for a premise to be false. Take questionable analogy. That can be put as a valid argument where you've got a premise which asserts a false analogy. That's another way for a premise to be false. Sure both of these fit in your second category. But it's nice to be able to make a distinction between the sorts of mistakes here since they happen so commonly.

                          Custom: the point is that the argument does not provide enough for rational belief. There may be other arguments with premises that do provide that, just not the one in the example.

                          [edited for a typo]
                          Last edited by sordavie; 06-20-2006, 06:13 AM.

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                          • #14
                            Re: How to Spot a Bad Argument

                            Originally posted by sordavie
                            Oops I made a mistake in explaining denying the antecedent. That's probably confusing people. It should be:

                            Denying the antecedent: take 2
                            Ok, that one makes much more sense. Now its the logical form:
                            Given: If A, then B
                            Given: Not A
                            Therefore: Not B

                            Which qualifies as a formal fallacy, without needing to call upon informal fallacies at all.

                            Kerostasis, but on your point of not making distinctions between certain informal fallacies, I don't see why we shouldn't. Maybe you have no use for such fine grained distinctions. But that doesn't mean those who study them shouldn't make them or that they aren't there. Circular argumentation doesn't fall in either of your categories. Slippery Slope is another that doesn't fall into either of your categories. (I also take it A is supposed to be "the argument is valid, but offers an irrelevant conclusion, or proves something different from what it was intended to prove" since arguments are not true or false but valid or invalid.) As for your second category, I take it there are many ways a premise can be faulty. Some of these ways are common enough to be given names.

                            For instance, if you take a valid argument that's guilty of false dilemma you've got some premise which does not present the full range of choices. That's one way for a premise to be false. Take questionable analogy. That can be put as a valid argument where you've got a premise which asserts a false analogy. That's another way for a premise to be false. Sure both of these fit in your second category. But it's nice to be able to make a distinction between the sorts of mistakes here since they happen so commonly.
                            I can definately see where you're going with this. I'll have to think about it some more.

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                            • #15
                              Re: How to Spot a Bad Argument

                              Wow

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