Arguing · Investigation

Bad logic. Some common fallacies

I was talking about assessing documents (and statements) to see whether they are “logical”.

Critics of “logical communication” will quite rightly make the point that a document can be logical, but boring, irrelevant and completely un-compelling. This is true and I should get to talking about it soon.

But before I do I wanted to talk about “Bad logic”.

A lot of the communication I come across consists of the message “This is true so that is true” which is a logical enough structure.  But is the statement “This is the CFO’s most important project, so we need to deliver it on time” actually logical?

It may be logical to infer from this statement that we will get in trouble if we tell the CFO that her most important project is running late. But this presupposes that delivering it on time will meet the CFO’s needs.

For example, would she be happy if we deliver an embarrassing debacle exactly on time, or might she be a little happier if it was a week late and seen as a great success.

The statement also presupposes that being the CFO’s most important project (an often dubious claim) makes it important. But what if the CFO’s interests are not aligned with those of the customer, the shareholder or the law?

Many business communications rely on inferences (or even implied threats) that require the reader to fill the blanks in for themselves. This is good if you are a dodgy scam artist whose argument will not stand up to critical evaluation, but not so good if you want to convince cynical readers, present a valid case or make a judgement on someone else’s message.

So here is a list of common Fallacies, or flawed arguments. I hope it will be useful in reviewing your own work and in reviewing other people’s.

Fallacy Example / Description What to ask
The speaker is important so the message is true. “The CIO always says …” or “John has already agreed to this”. Implying the message is as credible as the messenger Why does X say that? What would they know/not know about the subject? If they did not say it, would it be the right conclusion?
The speaker is unpopular so the message is false. “Bad employees always complain about safety .. “ Why do they always say that? Is this person really an X? If they are then is that relevant? Most importantly, let’s forget who said it, what evidence supports or discounts the logic of the statement rather than the speaker.
Complex equivalence He is a hard worker. He will deliver the project on time. Add if/then always – “If he is a hard worker then he will always deliver the project on time” – now ask “are projects always delivered on time if people work hard? What exceptions would there be?
I’m not saying that .. “I am not saying that we can’t do it but” Really? If you were saying it, what would the reason be? Without using the word “not”, what are you saying?
False choice “You can buy the car today or you can pay more next week”. This often hides multiple other options – like getting a better price, buying a different car. If there was another option- what would it be?
Quoting a maxim as a fact We pay market based salaries, so Jo is paid fairly. Swap the sentence around and add an if then – “If Jo is paid fairly then we pay market based salaries” – so how do we demonstrate that Jo is paid fairly?
Its not what we do “Everyone knows …”, “the way it works is … “ What would happen if we did that differently? Even if everyone knows, what if one person thought differently?
Negative generalisation “They didn’t promote me so management don’t reward talent What other causes might have applied to this specific situation? If the generalisation is true, is it always true? Are there exceptions?
Dodgy analogy “like a snake in the grass”. Analogies help give context but can also display bias Is this analogy helpful?  Putting aside the analogy, what statement is actually being made? Does this stack up?
Red herring/pet project “Employee safety is important, but what about shareholder value” If the new topic is important, is it relevant to the existing topic?  Take it out and put it in a different argument/section/presentation then get back to the original one.
Precedent / dominoes “This would set a precedent … “
”If we say yes to this, then the next thing will be … and then … and then the world will end”
Is the argument sound?  What is wrong with setting the right precedent? Will the rest actually follow? What if it did?
Tit for tat “Yes, we are behind schedule but project X is way off target” What are we doing again? Why? What is the implication of what we are doing?
Wrong anchor / comparison “Other projects typically spend under $50K” Is that relevant? How are they different/the same?

Not all fallacies are linked the incorrect conclusions. But they have a habit of distracting us from the real argument. And they can make an argument seem sensible to those who already support it but flaky to those who oppose it.

So even if you think the conclusion is right you might find that using these fallacies inhibits your ability to convince you opponents, or enter a meaningful conversation with them. Similarly, if you look for these fallacies in the information you are given, you will often stumble upon the weak points in an argument, or the areas that the author did not really want to explore.


3 thoughts on “Bad logic. Some common fallacies

  1. Fallacies are not an island to themselves, they are often used to promote consistency

    Consistency Theory….
    Step 1: People seek consistency in their belief
    Step 2: Inconsistencies create a state of dissonance (conflict).
    Step 3: Dissonance drives us to restore consistency.

    4 different tactics for getting rid of dissonance (conflict).
    First, deny it. Just pretend like it didn’t happen. Ignore it. It is not there, never was, and never will be. “Everyone can get helathcare, just go to the ER”
    Second, swamp the dissonance. Sure some information doesn’t make sense, but remember all those other times when it did? The goal here is to overload all the conflicting information with a ton of good memories and thoughts. “I know people who don’t have health insurance, but get medical attention”
    Third, change your expectations. Some people would call this a form of rationalizing.. Here you are trying to make sense out something that really did happen. “People who don’t get medical care are to blame for not seeking treatment”
    Fourth, you evaluate the event and instead of responding with dissonant thoughts (“I can’t believe that people can’t get medical care”) you actually change your evaluation and find the best possible outcome. ‘”The governement has their own agenda, they are socialists!”
    Consistency theory explains why people deny facts. If you expose yourself to discrepant information (e.g. reading articles on the problems w/ the health care system), you will probably produce inconsistencies which will lead to dissonance, which will lead to mental work. To avoid all this trouble, people “selectively expose” themselves to information when possible. That is, they will seek out things they agree with, but will avoid things they disagree with.


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