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"I've always argued P. But in this case, I believe not-P. (Implied conclusion: in this case, not-P)"

One hears it from political commentators and others who think that their own personal system of beliefs is somehow so thoughtfully constructed and coherent that their merely taking the opposing not-P side somehow counts in favor of not-P in the particular case.

Of course the details of how it is presented matter, but the obvious rejoinder is something along the lines of: "Oh, well, thank goodness you can at least see the error of your previous way of thinking, at least in this case."

But is there a name for this annoying manner of arguing? Is it a known fallacy or variant of one?

UPDATE: Very many good replies. Thinking about it more, what annoys me is that I think we all argue this way sometimes and that it is useful and harmless to do so, but when pundits do it, they are helping themselves to credibility that they are not entitled to.

So, here's a useful example. Imagine a husband and wife and the wife is a book reviewer. The wife says, "Well, usually I can't bear detective novels, but this one is quite good." Here the husband has been given some useful information; perhaps he doesn't even want to know the details, e.g., just wants to understand what all the hoopla is about this novel. He and his wife know that he values her opinion. She's already earned the credibility in his eyes and furthermore that is known by her.

When a pundit does it, he's assuming his credibility can be taken for granted. At a minimum, he's assuming that his having passed judgment in many prior cases gives him some kind of credibility. But his audience is large and anonymous.

So I guess that's why I'm still thinking about this. How much credibility is somebody justified in assuming his (anonymous) audience has given him?

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    But, in principle, why a fallacy? We may change our ideas... Commented Aug 29, 2023 at 17:31
  • Of course, but that is not the way they employ it. The conclusion not-P is always implied.
    – mster8390
    Commented Aug 29, 2023 at 17:37
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    Special pleading, "an informal fallacy wherein one cites something as an exception to a general or universal principle, without justifying the special exception". Keep in mind that, colloquially, "universal principles" are typically stated with implied common sense and/or ceteris paribus restrictions that are not spelled out (or even thought through ahead of time), see Default logic. Even "do not kill" has implied exceptions, so this is often not a fallacy.
    – Conifold
    Commented Aug 29, 2023 at 17:57
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    More generally, it is perhaps an example of claiming I must be right because I have thought about this and I have allowed for an exception, so I am being clever. It is similar to how people say, "I used to believe that," as if that fact counts as evidence against some position. People change their minds and that is a good thing, but it is not in itself evidence for anything. I wouldn't worry about putting names to fallacies. That is a silly thing that newbs and wannabes do; it has little to do with real logic.
    – Bumble
    Commented Aug 29, 2023 at 21:12
  • @Bumble. Right. I like your examples. But don't you think that there a taxonomy of common errors is there to be discovered in the wild? It's not part of real logic I agree nor even really epistemology, but it still seems perfectly defensible to layout the terrain. I've seen diagrams with somewhere around a 100 different common errors.
    – mster8390
    Commented Aug 29, 2023 at 21:40

5 Answers 5

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It is simply and surely a non sequitur.

How often you believed in a proposition in the past has no bearing on the truth of the proposition now. This is only true if the implied conclusion is not-P in your case.

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Is this logical fallacy?

Whether this argument requires a fallacy depends upon the content of this particular argument.

It might well be that an internally consistent set of assumptions will allow this speaker to carve out a personal exception to the overall rule.

But if there are no such assumptions, then, yes, somewhere the speaker will have to start fudging the argument with phony definitions, unspoken assumptions, and plain old fallacious thinking. These methods make the argument fragile and subject to exposure, typically by a reduction to absurdity when the ideological argument is compared to real world examples.

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It is not a formal fallacy.

A formal fallacy can only apply when the speaker is in some fashion invoking formal logic. This need not be explicit. Indeed, outside of formal mathematics or philosophy one rarely expressly states that they invoking formal logic. If someone uses a form that looks like a syllogism for instance but uses an invalid pattern such an undistributed middle then it is perfectly proper to point out the fallacy.

But things which actually are logical fallacies can be perfectly legitimate and defeasible forms of argument outside of formal logic.

For instance, ad hominem attacks in a situation of formal logic are one of the best known logical fallacies and they are improper in situations of formal logical. But, at least if they go to credibility, they are defeasible and indeed routine in a courtroom and useful in informal reasoning.

Whether it is defeasible reasoning or an informal fallacy depends on the circumstances.

Whether it is reasonable and legitimate for "I've always argued P. But in this case, I believe not-P. (Implied conclusion: in this case, not-P)" depends on the circumstances and whether they can provide a reasoned explanation for why P is true in most cases but this is an exception. If they cannot provide an explanation for why this case is different, then it is a form of "special pleading" as the term is used in philosophy (note that has a very different meaning in some legal systems). Special pleading is essentially an informal fallacy where you claim an exceptions without being able to give a reason for why there is an exception.

But if you can give an explanation that is itself at a minimum a defeasible argument, then it is not special pleading and is at least potentially legitimate.

For example, "I've always argued that you should not kill another human, but in this case where the killer was protecting a helpless toddler from being murdered, I believe that the killing was proper". You may not agree with the reasoning. There are people that believe that killing a human can never be proper under any circumstances ever. But it is a reasonable and defeasible argument and not a fallacy.

Also, this type of thing comes up in law constantly. There are all kinds of general rules, that then have laundry lists of exceptions. You should generally perform your obligations under a contract, but if the other side repudiates the contract you may be excused from performance. It is usually theft to take something of value that belongs to someone else, but if taking it was necessary to save a life it may be justified so that the law will find it was not theft at all.

(For clarity: I am using defeasible in the philosophical sense of defeasible reasoning in which an argument may be reasonable and rationally compelling but does not provide deductive proof. In other words, a defeasible argument is generally a reasonable one but does not provide formal proof in the way that a valid syllogism or mathematical proof word. Defeasible has a related but separate meaning especially in law of something that capable of being defeated or invalidated.)

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Have you heard of fallacy of accident? A general rule is applied to every case, I guess indiscriminately, even when a strong argument exists that a particular case is an exception (to the rule). Hence follows, "well, in this case, I'd have to say elephants do forget."

Fallacy of Accident

Follow the links.

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Fallacies usually refer to a fault in an argument in deductive reasoning. So you have a set of premises (usually a general rule and a specific application) and you derive a conclusion based on these premises. Now if the premises are true the conclusion MUST be true as well (validity) and if the premises are indeed true than the conclusion IS also true (soundness).

Now all fallacies are non sequitur (=does not follow) meaning something somewhere got wrong and the conclusion does not follow from the premises. And as deductive reasoning works with claims of absolute truth value, just 1 counter example suffices to disprove the argument, even if it's just a theoretical one.

The problem is that we have a really hard time even determining the truth value of pretty much ANY claim in the real world. So this kind of thinking is usually limited to the abstract and theoretical where we take certain things for granted arbitrarily and then reasoning our way from there.

So if your commentator indeed makes the claim that P is always the only correct approach, then not P is NOT AN OPTION.

For him to pick not P would necessitate to give up P and take a severe hit to his credibility and claim of expertise given that he wholly put himself behind a claim that was false. Implying that his credence in the claim was more based on confidence and charisma than facts.

If he instead just happens to pick P all of the time, because he didn't come across a case where not P is the better option, then there might not be a contradiction at all. On the contrary it's a fallacy to assume he must pick P all the time just because he picked it all the time so far. That a trend continues is an inductive argument and depending on how long the streak had been, it's a weak or strong one, but the trend alone does not necessitate that it continues. See gambling...

Now to be fair if he is making the claim that "I always pick P, so me picking not P is an indicator that not P is correct", is again an appeal to a trend in that case "I was right all the time, so I will continue to be right" or "You liked what I did so far, so you'll also like my new stuff". Which again is probably likely (to varying degrees), but not a certainty. Like anybody can probably name counter examples of people "selling out", changing their style or even just figuring out that what you liked about them was never what they considered to be an essential part of themselves.

There's also another case that a 3rd party says that about them. So "They've always said P and now EVEN THEY say not P". Where the implication is that of a phase transition where the amount of counter evidence finally came up to a threshold where even the most fervent deniers had to give up their resistance. Though again that is just one interpreting narrative, but there are countless of other reasons why they would have changed or not even changed their position (see examples above).

You could also make the argument that a change in one's core positions takes more energy/thought/incentives than a continuation of holding a position given our psychological biases. So a change in position could actually mean that person has applied a higher than average level of thought (with respect to THEIR average) to that topic (whether that means much is a different topic). But that's also just a heuristic not a hard and fast rule and you can find counter examples like people who faced incredible harm and backlash for holding a position or opportunists who regularly move positions depending on what's better for them now or the incentive to change might not have come from arguments and deep contemplation, but from money and/or coercion.

It might work as a heuristic in some cases, but it's not sufficient for a general rule. So in the first case it's about the success/failure ration being above 1 in the 2nd case it must be correct all the time.

Also for completion. Being wrong and admitting that is not necessarily a failure or a personal flaw of one's judgement and a lack of expertise. If you deal with the facts as they unfold it's an inherent risk of the craft to be wrong and not necessarily a problem of the individual. However how much that effects them personal depends on how well they sourced their claims, made their reasoning transparent, whether assumptions were labelled as such and whether uncertainties were identified and made transparent, made clear that he's arguing with heuristics rather than general rules and so on. Then they've displayed enough skill and expertise to argue that they weren't the part in the system that failed.

While if they do the opposite, exaggerate claims, merge facts and fiction, leave no room to follow their reasoning and generally make themselves some kind of magic 8 ball that just happens to be right more than wrong, then long list of failures or a critical failure, will lead to them being viewed as defective at what they do. Regardless of whether they actually were the part in the system that was actually defective.

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