This is an import from a RationalWiki essay originally started last year following some argument or something about something, I forget. The links are all still to the RW inter-linked articles, as copy-pasting HTML-formatted text is remarkably efficient! There are a few stylistic/rhetorical changes for this version.
Argumentum abusi fallacia (Latin for “argument of the abused fallacy”) is the incorrect use of a formal or informal logical fallacy. As there is an absolute myriad of fallacies to choose from, it’s quite easy to not be entirely familiar with all of them.
False accusations that someone is making a fallacious argument, even when they’re not, become common. Someone might be making a bad or incorrect argument, but there are ways to be wrong without really being fallacious about it and there are ways to be right while still being fallacious.
One example might be the assertion that “women deserve equal treatment because they’ve been second-class citizens for years” – a morally sound conclusion but, technically, a non sequitur when you think about it (see the “is-ought” problem).
There are also ways to counter an argument without providing a list of fallacies – in the business we call these things “counter” arguments. Science does this all the time; we correct things by presenting superior evidence, rather than declaring previous theories to be somehow fallacious (and if you think “being incorrect because of evidence you didn’t have access to at the time” is a fallacy, you’ve largely missed the point).
The use of argumentum abusi fallacia is something of an argument by assertion, in which an attempt is made to refute an argument simply by citing the name of a fallacy. Almost certainly without any further explanation of why.
This is often a result of falling into skeptical jargon, or just discovering that there are terms not just to describe that someone is wrong but why they’re wrong. So, thanks to convenience and in an effort to show off this new-found knowledge – and, hey, some of it’s in Latin! – someone might be very keen to drop the name of a formal or informal fallacy into conversation. However, just because you can reduce why someone is wrong to a single, fancy name, doesn’t mean the names of fallacies can be thrown around at will and automatically be correct. Arguments need to be demonstrated as being fallacious, and usually this is possible without using any Latin at all. Although this list is a little pedantic, the important thing remains to understand why something is incorrect or fallacious, rather than get the name right.
Unless you’re attempting to answer a Gish gallop in real time, in which case you might not have much choice but to just go for the shorthand. So long as you use the shorthand correctly, of course.
Formal and informal
In short, a formal logical fallacy is a fallacy in the structure of an argument. If you distil the argument down into symbolic logic, which is the quasi-mathematical way of representing arguments and implications, a formal fallacy is one where the pieces simply don’t fit together. Because this is all represented symbolically, what those letters actually mean doesn’t count. In a formal statement like “P → Q, P, therefore Q” it doesn’t matter what P and Q stand for.
The formal fallacies are rarely misused; though mostly because it’s far easier to take issues with content and style than to break an argument down to a logical form and track down the errors – and if one was to do that, then the fallacies become evident and difficult to misinterpret or produce a false positive. For instance, accusations of a non sequitur argument are usually valid, since that disconnect is easy to spot and demonstrate.
Informal logical fallacies are issues with the content of an argument. I.e., what the P and Q actually stand for. Unlike the formal logical fallacies, the informal fallacies are rife with pitfalls where they are misused, creating a ton of distracting false positives. At worst, their misuse comes from an inability for someone to create a new argument of their own or to address an opponent’s points; they simply accuse them of making a fallacy and have done with it.
The examples below chart the most common offenders.
Example: Special pleading
The cosmological argument as made famous by St. Thomas Aquinas and others reads roughly as follows:
Everything that exists requires a cause. There cannot be any infinite regression of causes. Therefore, the universe must have a first cause: God.
The trouble with this argument is that it exhibits special pleading. God is arbitrarily, without any supporting reason, exempted from the requirement that “all things require a cause”. Often the response to this argument is “why can’t the universe be acausal if God can be?” and thus the special pleading begins. Either God is made an exemption “by definition” (a very strong case of special pleading) or other wild assertions are made that make God “not count”. This is a legitimate fallacy: God needs a real reason to be exempted from the premises of the arguments.
So, in response to this, the argument has been modified slightly. This is the Kalām cosmological argument, touted ad nauseam by William Lane Craig, which usually uses this slight alteration over the version above:
Everything that begins to exist requires a cause. There cannot be any infinite regression of causes. Therefore, the universe must have a first cause: God.
One of the reasons behind this modification is that it appeals to our experience of naturalistic reality; everything we see come into existence does, in fact, have a cause. So, if somebody were to dismiss this modified version of the argument with “that’s special pleading!” it would be an incorrect use of the fallacy. This is is because the modification explicitly exempts an “eternal” God from the need for a cause, so does not contain any special pleading. The underlying logic is on better and less fallacious grounds as “special pleading” is a formal logical fallacy – a problem with the structure, not content. Special pleading is stating 
⇒
, and giving ad hoc exceptions. There are a multitude of other issues with the Kalām argument, but since the exceptions are, in fact, built into the logical conditions then there is nothing “special” about the pleading, ergo, no fallacy.
Example: Ad hominem
An ad hominem argument, from the Latin for “to the man”, is something that doesn’t attack the questions and points at hand, but the messenger and the person delivering it. This is one of the most common misuses of an assertion of fallacy because people can all too easily confuse ad hominem with “crass insult”.
If someone calls someone else a ‘total douchebag cunt-faced prick-stain’ out of the blue in a discussion, it might be mean, it might be unproductive, hell it might even be fair and correct, but it is not necessarily fallacious. It doesn’t have any particularly flawed logic to it, it’s just an insult. Ad hominem attacks dismiss an argument because of a completely unrelated property of the person delivering the argument.
Consider the following:
The war in Iraq is illegal because George W. Bush is an incompetent buffoon.
This sort of thing is an ad hominem attack (and is a specific logical fallacy) because, buffoon or not, Bush’s intellect has little bearing on the validity of a war; the validity of the war is what impacts the validity of the war. However, we can rephrase this slightly.
George W. Bush is an incompetent buffoon because the war in Iraq is illegal.
This is on slightly firmer ground. In short, while it might still be irrelevant, Bush’s lack of brain isn’t being used to justify a legal status. But his actions and comprehension of a legal status can be used to infer his state of mind. It’s easily arguable and conceivable that someone engaging their country in an illegal war could be described by the words “incompetent” and “buffoon” amongst several others. Yet, if faced with no alternative rebuttal, this might well be accused of being an ad hominem attack, just because it makes an egregious personal insult.
(Note: the two above are forms the same ideas with the implication reversed: ⇒ and ⇒. For a treatment of why these aren’t the same statement, see affirming the consequent and its statistical cousin confusion of the inverse. The logic is non-commutative in these cases.)
A few others
Here is a brief run-down of a few other pieces of skeptical jargon that occasionally get misused:
- Argument from adverse consequences
- This is the fallacy that states that because X is unfavourable, or would cause problems, X isn’t true. It is fallacious because the effects of a hypothesis have no bearing on its truth value – objective reality cares little about whether it screws us over. However, there are cases where there is no “truth value” to be found. For instance, social policy. Here, consequences of a decision are all we have to determine a correct course of action – in terms of setting a policy or making a decision, the consequences are a stand in for the “evidence” you would expect to see from a testable hypothesis.
- Appeal to authority
- As noted in the relevant RW article, appeal to authority is perfectly valid when it’s an appeal to a relevant and experienced authority. Talking to Brian Cox or Stephen Hawking about physics, and Richard Dawkins about evolutionary biology, for example is fine because they have studied and contributed to these subjects. While it is true that even in these cases their arguments need to be judged on their own merits and aren’t correct because they are authorities, this fallacy is often mistaken as a carte blanche to ignore anything said by an authority, or to ignore anything externally referenced to a person.
- Begging the question
- People often use this to mean “raises the question”… but that’s something else entirely. Circular logic can often be easily confused with just normal logic as any individual logical step should be so undeniably sound that it might seem, to the untrained eye, just to state the obvious. Consider P → Q, P, therefore Q, for example – this is formal logic working at its finest, but “P, therefore Q” might very easily appear circular.
- Confirmation bias
- Remember, just because you’ve found evidence that still supports your hypothesis, doesn’t mean you are necessarily guilty of confirmation bias. The standard model of particle physics has withstood a lot of testing, but those testing it aren’t guilty of confirmation bias; because this fallacy is a description of how you go about searching for that evidence by building experiments and tests that can only prove your point and may never fail. Specifically, whether you bother to look for something that will disprove your point. The Wason card problem illustrates the point of a confirmation bias nicely: if you first seek out evidence to disconfirm the hypothesis of the problem, you can solve the problem in fewer card turns and the falsifying test always needs to be performed, while the confirming test is irrelevant to the hypothesis given.
- Correlation does not equal causation
- Often, this can be cited in a way that almost completely denies the correlation too. If two events (P and Q) correlate significantly, then the probability of you getting P when you have Q is still higher than when you don’t have it. A lack of causality between the two still won’t stop this if the correlation is experimentally verified. For instance, in the textbook example of shoe size correlating with reading ability, the main cause is that both correlate quite nicely with age – but unless you control for age, experience and education, the correlation between reading ability and shoe size will still exist. Indeed, more precisely determining causality from data is done this way; by controlling for confounding variables to see what relationships remain.
- Equivocation
- Equivocation is effectively an illusion of language only – the fact that words can have multiple meanings and definitions in different contexts and so might get confused. It’s a simple mistake, really. For example, conflating biological evolution (Darwinian natural selection) with stellar evolution that tracks the lives of stars. Sometimes people will call “equivocation” when someone is using an analogy – but providing the person making the argument by analogy knows what they’re saying and where the analogy works and where it fails, there is certainly no equivocation involved.
- Extraordinary claims require extraordinary evidence
- This quip has often been used to describe how believing in ghosts requires a substantial degree of evidence because such a concept would go against what we already know – it would rattle the whole of science far more than merely not finding the Higgs boson would. But sometimes it can produce a straw man that’s used to dismiss any and all evidence for something because it simply isn’t miraculous enough. Homeopathy would just need a statistically significant improvement over a meta-study to prove it works for a particular illness, it wouldn’t need to magically cure every cancer it’s tried on to prove itself (the fact it does neither is beside the point, it’s about correctly judging what evidence is required).
- Slippery slope
- “If you allow X, then Y and Z are certain to follow – therefore X is bad.” This is only an invalid argument under certain conditions. Specifically, how realistic is the slope involved here? Raising house prices on one property is likely to cause a race to increase the prices of the surrounding houses, this slope is fairly realistic. Gay marriage leading to the legalisation of bestiality is significantly less realistic on account of the principle of informed consent. This is tied up with argument from adverse consequences.
- Straw man
- A straw man argument is one where a person deliberately (and perhaps knowingly) sets up a false version of what they’re arguing against in order to defeat it. Straw men are often seen in protracted arguments where a particular “party line” exists; for instance, the crocoduck as a supposed “example” of evolution – straw man versions of creationist beliefs appear equally often, particular amongst parodists. However, true straw man arguments tend to exist mostly when speakers or writers have had time to process what the other has said, and the straw man is really identified as such when they continue to use those arguments despite repeated corrections. The misuse of the straw man idea appears in a few different ways.
- What tends to happen in quick-fire debates is that someone will accuse the other of forming a straw man argument, when really all that has occurred is a misunderstanding – and 90% of the time, the responsibility for the misunderstanding is the person doing the talking, not the listening. Accusing an opponent of forming a straw man argument forms a tactic to deflect people from noticing that the point may not have been laid out very well to start with (in short, people are stupid and don’t explain themselves well; but doing this intentionally is something else entirely and may even count as obfuscation).
- A “straw disclaimer” can exist in which someone is saying that they’re arguing for x but specifically say they’re not arguing for a slight modification of x. If a counter-argument suggests that there is no practical difference between the two, it’s very easy to counter it completely by shouting “straw man”. This often crops up when defending mentioning slavery in the Bible; as the Biblical rules refer to how to treat fellow Hebrews and don’t refer to “chattel slavery” – even though, for most practical and moral purposes, there’s not a tremendous amount of difference.
- As a response to using a reductio ad absurdum where someone is shown to endorse a position they didn’t explicitly endorse initially. While a reductio ad absurdum argument can produce a straw man, this isn’t always the case and the correct response is to demonstrate the fallaciousness of the reductio argument, not to dismiss its conclusions outright.
Conclusions
Okay, so that’s long, and slightly rambling. I’m not even going to say all of the above is even “true”, because I’m not a prescriptive authority on what “is” and “is not” logical. All I can say is how I see it. But I can end with this piece of advice; don’t even bother learning the “correct” use of fallacies. Just say what you mean, say what is wrong with what someone says. Is someone making a “straw man” of your argument? Don’t say a straw man, just say “that’s not what I mean, and I would like to know how you came to the conclusion that I said it”. Is someone insulting you? Don’t say ad hominem, just move on and focus on what substance you can actually find amongst the dreck. It’s not that hard, surely…
Spherical Bullshit 