The Fallacy Fallacy

People love to collect lists of "fallacious" argument forms, with which to club opponents.  But beyond a few logical errors, specialists have found little support for the idea that one can tell an argument is bad just by looking at its form.  From a Synthese article last September: 

Lists of so-called fallacies of argumentative discourse date back to Aristotle’s Sophistical Refutations and his Topics, and have received further additions throughout the ages. … the kinds of things intended is clear: petitio principii (or `question begging’), arguments from authority, ad hominem arguments, or Locke’s argumentum ad ignorantium (argument from ignorance). These fallacies have accumulated in logic textbooks and have been dubbed "informal" fallacies because it has not been possible to give "a general or synoptic account of the traditional fallacy material in formal terms" … Such analytical treatment has seemed elusive because some of the fallacies are logically valid, but seem to fail as arguments nevertheless. For example, begging the question is deductively valid …  it is increasingly a problem endemic to the field of logic that, in some cases, arguments that seem to be of the same general type as the fallacies are (in some sense) reasonably good arguments, that are, and ought to be, acceptable as legitimate ways of rationally persuading someone to accept a conclusion.


Thus the field of informal logic is at a crisis point. … There seem to be two paths: (i) try to refine the formulation of the structural characteristics of the argument, such that the seeming counterexample is now no longer part of the fallacy, as now more exactly defined, or (ii) accept that fallacies are fallacies not because of their structure alone. A popular response to the problem has been that informal logic deals with arguments in context – and it is the context that is responsible for the differential acceptability of arguments with the same structure.

The authors, Ulrike Hahn and Mike Oaksford, try to offer Bayesian concepts which can make clear how context matters:

We examine in detail three classic reasoning fallacies, that is, supposedly "incorrect" forms of argument. These are the so-called argumentam ad ignorantiam, the circularpetitio principii, and the slippery slope argument. In each case, the argument type is shown to match structurally arguments which are widely accepted. This suggests that it is not the form of the arguments as such that is problematic but rather something about the content of those examples with which they are typically justified. This leads to a Bayesian reanalysis of these classic argument forms and a reformulation of the conditions under which they do or do not constitute legitimate forms of argumentation.

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  • http://www.mothering.com/discussions/forumdisplay.php?f=44 Acksiom

    “In each case, the argument type is shown to match structurally arguments which are widely accepted. This suggests that it is not the form of the arguments as such that is problematic but rather something about the content of those examples with which they are typically justified.”

    Wait — isn’t that itself an example of the fallacy of the Appeal to Belief?

    Such structural matching rather suggests to me that these widely accepted arguments are merely similarly fallacious, and that instead it is indeed their abstract form that is problematic, and their specific content which is being relied upon to conceal their lack of validity.

  • TGGP

    A google search for “circularpetitio principii” or even just “circularpetitio” returns no results. Is that begging the question?

    Since logic was supposedly invented by the greeks, shouldn’t we be using greek terminology rather than latin? As an added bonus, the former is not a dead language!

    One of my favorite bloggers used to be Ilkka Kokkarinen of Sixteen Volts (after his university got wind of it he shut it down and switched to the Fourth Check Raise) had a good post on how logical fallacies resemble many perfectly good arguments.

  • http://cob.jmu.edu/rosserjb Barkley Rosser

    Well, it should be kept in mind that one can “know” something is “true,” even if it cannot be proven, or, to be more precise, is associated with a logical contradiction within the logical sytem out of which it comes. This is deeply connected to the Godel problem.

  • http://profile.typekey.com/brucekbritton/ Bruce Britton

    Isn’t this problem also true about the lists of cognitive biases? We love to collect lists of cognitive biases, which we use to club opponents. And in many cases we can’t tell that an arguement is bad just by looking at whether its form matches the form of a cognitive bias. For example, there are arguements that are based on the availability heuristic, but have true conclusions, and ones that are false. Similarly for the representativeness heuristic: sometimes the conclusions based on it are true, and sometimes they are false. It is true that the Aristotelian-type logical approach to arguement has shortcomings, but the work of Chaim Perelman provides a corrective to many of the problems. Perhaps a post on his work would be useful.

  • http://profile.typekey.com/brucekbritton/ Bruce Britton

    Many of the cognitive biases have directly opposing cognitive biases. For a particularly good example, look at the opposition of the Ludic Fallacy against the probabliity biases (gambler’s fallacy, etc). In any particular case, either one or the other of the pair of biases may be a correct description of the situation, but not both, because they are mutually exclusive. So with cognitive biases, just like ‘logical fallacies,’ you have to look at the subject matter context in order to come to a correct judgement about whether the arguement is a good one.

  • http://profile.typekey.com/sentience/ Eliezer Yudkowsky

    You’re certainly going to have problems if you think of bias-resemblance as being deontologically prohibited as bad conduct, like flashing yourself in a public area. Certainly an argument can exhibit bias and yet come to a correct conclusion – the world’s stupidest man may say the sun is shining, but that doesn’t make it dark out. The question is whether that kind of argument reliably produces good answers, and at what degree of reliability.

    Some “fallacies” are bad ideas not because they are totally nonfunctional, but because of their side effects or their very weak reliability. Ad hominem short-circuits a more rigorous process of argument; appeal to authority may not be sufficiently reliable.

  • Doug S.

    “Ad hominem” when used correctly is an attack on the credibility of the speaker of an assertion.

    I think the structure of the argument, when used correctly, is something like this:

    You have asserted X.
    You have some characteristic that would cause you to assert X whether it is true or not.
    Therefore, your assertion of X is not evidence that X is true.

    Example:
    You assert that cell phones do not cause brain cancer.
    You are a spokesperson for a cell phone manufacturer, so you would be likely to say that even if it were false.
    Therefore, I will ignore your statement when considering the issue of whether cell phones cause brain cancer.

    Where the “ad hominem” argument becomes a fallacy is when you use it to claim that because a person with particular attributes says X, X must therefore be false. After all, a stopped clock is right twice a day!

  • Ann

    The weakness of the ad hominem argument even “when used correctly” is suggested from Doug S’s description of it, fleshed out a little.
    Someone asserts x.
    Anyone who asserts x probably has some reason for doing so, which reason might derive from a characteristic that would cause him to make the assertion even if it were false.
    Therefore, no one’s assertion of x is evidence that x is true.

    An argument that hinges entirely on the credibility of its declarant is a weak one, and should be considered only when no better form of evidence is available. However, opposition to an argument that hinges entirely on an attack on the credibility of its declarant suggests a lack of interest in the evidence upon which the declarant may be basing his assertion.

    “I will ignore your statement when considering the issue of whether cell phones cause brain cancer because you are a spokesperson for a cell phone manufacturer” may superficially sound more reasonable than the fallacious “I will conclude your statement is false for the same reason,” but if the goal is truth, no assertion can be dismissed out of hand, merely because of its declarant’s possible bias.

  • http://asecondhandconjecture.com/?p=948 A Second Hand Conjecture

    Questioning fallacies, begging for answers

    At Overcoming Bias Robin Hanson points out that logically many fallacious forms of argument are not necessarily so. So is question begging inherently fallacious? It seems context matters. The comments are juicy.
    Much more here. Conclusio…

  • http://liberalvichy.blogspot.com/ Vichy

    I typically like to explain the exact error, partially because I can’t always remember the name or spelling of a particular fallacy.

    And I think sometimes it is just personal laziness and a presumption of knowledge in the audience.