Poor reasoning and fallacies

Poor reasoning and fallacies

A logical fallacy is a failure in reasoning that leads to an argument being invalid. They are like cracks in the foundation of a building: if they are present, the building is going to fall down. So detecting fallacies is a very important part of making yourself critically skilled: if you know what fallacies are, you can both avoid making them yourself when you present an argument, and spot them when others are using them.
And use them they do. Everyday, you will probably come across dozens of fallacies. Some are present innocently – someone using a line of reasoning that is incorrect by accident. But some are far from innocent, and are deliberately employed to lead us astray. The advertising industry, politics, the media, law – in all of these areas of life, fallacies are used and abused, and more often than not, remain undetected by an audience that ends up tricked and misled. So learning what fallacies are, and being able to identify them will help you hugely when you get into any kind of debate with other people, in school, and outside of it.
They fall into two categories – formal fallacies (sometimes called logical fallacies), which are fallacies because of the way they are incorrectly structured logically, and informal fallacies, because the meaning of the words and what they express has been used incorrectly. An example of these two types of fallacies could be-
A formal fallacy:

Some IB students study History
John is an IB student
Therefore, John is studying History

This is a fallacy because although we can say that it is possible that John is studying History, we cannot say that with certainty, because only some IB students study History. Therefore, there is a problem with the logic of the structure.
An informal fallacy:

TOK teaches people how to argue
People argue all the time
Therefore, people don’t need to study TOK

This is a fallacy, because the meaning the word ‘argue’ is different in the first and second line, so the argument is built on an incorrect meaning. However, the difference between the two categories is often so fine that is extremely hard to tell when a fallacy is formal or informal. For that reason, it’s more useful to simply learn different examples of the most common fallacies, to enable you to identify them when you come across them. Many of them you will already have come across, but perhaps you have never known they had a name.

10 examples of common fallacies


1. Red Herring

This fallacy occurs when an irrelevant point is presented that leads the other arguer away from the original context of the argument. Red herrings cover a whole range of other fallacies – basically, whenever something irrelevant is used in an argument, it is a red herring.
Example: A politician being interviewed on television who is given a tough question about his controversial health policies. He replies that ‘the real question’ is why the opposition party has refused to give support to the government about their new laws on immigration, thus leading the interviewer away from the relevant issue.

2. Ad hominem (Latin, meaning ‘to the person’)

A type of red herring, an ad hominem fallacy is when one of the arguers begins to attack an aspect of the other person’s character involved in the discussion, and uses that as evidence for his lack of ability to make his point.
Example: An unmarried female politician is trying to bring in new laws to give women more rights from abusive husbands. Her ideas are criticized from the other political party because she has no husband herself, therefore lacks the right experience for this kind of issue. Such criticisms would be fallacious, since you don’t need to be married to be able to justify giving more rights to women.

3. Post hoc ergo propter hoc (‘after this, therefore because of this’)

This mistakenly links two or more unconnected events be proposing that one is the cause of the others occurring.
Example: Just before a general election, a country suffers a terrible snowstorm. When the voting has been completed, and the results are in, the party in power has lost. They blame their poor results on the weather.

4. Argumentum ad populum (‘appeal to the people’)

This is an argument that bases its truth on the fact that many people believe that to be the case. It is related to the rather unreliable consensus truth test.
Example: Because many people have bought a new record by the latest manufactured boy band, propelling their latest single to number one, they must be musically talented.

5. Gambler’s fallacy

The gambler’s fallacy is the belief that because a random event has happened frequently before, it has less chance of occurring in the future. The reverse gambler’s fallacy is to assume that because something has happened frequently, it will carry on doing so.
Example: You toss a coin into the air and see heads appear five times in a row. You then decide that tails have a better chance of turning up on the next toss. The reverse of this, of course, is thinking that heads will turn up again, since it seems to keep doing so when the coin is tossed.

6. Appeal to emotion

Appeals to emotions come in many forms, and involve using a form of emotion such as fear (terrorem), pity, flattery, and so on, to advance an argument. Because they rely on something that is irrelevant to the point of discussion, they are another type of red herring.
Example: A government insisting that the latest terror laws, that will violate individuals’ rights to privacy and freedom of expression, are justified primarily because of the threat posed by terrorists overseas. This is a fallacious argument, because the supposed threat does not justify the separate issue of whether people’s rights should be violated – that is another moral issue.

7. Historian’s fallacy (using hindsight)

One of the worst mistakes to make in history is to look back on an event and assume that those at the time had access to the same knowledge that we do about that event. This is also known as ‘using hindsight’.
Example: Saying that Chamberlain’s policy of appeasement was a terrible mistake – because it was obvious that Hitler was never going to stop expanding, and invade Poland – is a fallacy, because Chamberlain did not have that information available to him at that time.

8. Slippery slope fallacy

A slippery slope fallacy is when the person presenting their argument tries to strengthen it by talking about a catastrophic series of consequences occurring as a result of something they are opposed to.
Example: The headmaster of a school announcing that the amount of homework set for students will be increased by 50%. The reason for this, according to him, is that he fears that academic standards are dropping, which in turn will lead to students no longer being allowed into university, and having to take low-income jobs for the rest of their lives. This will mean that they will find it hard to support future families, have a healthy lifestyle, and keep together friendships. They will as a result suffer from depression and high-blood pressure, and, because they have little or no medical insurance, will die prematurely and painfully.

9. Inconsistent comparison

There are many fallacious ways in which comparisons are made to arrive at a conclusion. Inconsistent comparisons are when different elements of two or more objects or phenomena are compared, in order to arrive at a statement about one of them.
Example: The fuel efficiency of Car A is superior to that of Car B, its price is cheaper than Car C, and its safety features are more advanced than Car D. This common advertising technique attempts to make the first car sound like the best of the bunch, but of course this is a fallacy.

10. Argumentum ad vericundiam (appeal to authority)

This is when the authority or status of a person is used to support an argument. This fallacy is a one of the main features of the advertising industry, with the appeal of products they promote depending on its power.
Example: A well known Hollywood actor, who often plays the role of wise, authoritative characters, assuring you in a TV commercial that your money will always be safe if you join a particular bank. He acts out a short scene in which an attractive sales assistant begins to flirt with him only after he has pulled out his fancy yellow credit card to pay for something. Presumably it was his choice of bank – which you can emulate! – rather than his charisma, world fame, and vast wealth which impressed her.

Cite this page as: Dunn, Michael. Poor reasoning and fallacies (10th May 2013). theoryofknowledge.net. http://www.theoryofknowledge.net/ways-of-knowing/reason/poor-reasoning-and-fallacies/ Last accessed: 20th March 2018


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