Logical fallacies are some forms of unreliable reasoning or misleading arguments. Any structurally invalid argument is logically fallacious, but there are some recognized patterns of how a logical fallacy is committed. The following list will review some illustrative examples of them.   

Affirming the consequent:

  1. If P then Q
  2. Q
    Therefore,
  3. P

Denying the Antecedent:

  1. If P then Q
  2. It is not the case that P
    Therefore,
  3. It is not the case that Q

Scope fallacy

An invalid inference is resulted when a universal quantifier (all, every, each) falls within the scope of the existential quantifier (some, a, the, one).

Example of scope fallacy:

  1. Everybody loves to eat an apple pie.
  2. There is one apple pie that everybody loves to eat. 

We cannot infer 2) from 1), as an apple pie with universal quantifier (a) falls within the scope of an existential quantifier (one).

Fallacy of Equivocation

Equivocation is an argument that uses one word to mean two different things. So, the fallacy of Equivocation is committed when there is a switch of the meaning of a term during the reasoning.

Examples:

  1. A hair is always light.
    Therefore,
  2. A hair cannot be dark.

In this argument, “light” (not heavy) is switched to “light” (bright).

  1. Parents send their children to martial arts so that they could fight bullies.
  2. Parents expect that children will fight with bullies.
    Therefore,
  3. Parents encourage children to fight bullies. 

In this argument, “expect” (predict) makes a switch with “expect” (encourage).

Argument from ignorance

  1. We have no evidence that P.
    Therefore,
  2. It is not the case that P.

The fact that we have no evidence that something is true doesn’t mean that it’s false. Later, it may turn out that there is evidence for the relevant claim.

Similarly, if we have excellent evidence that P, it does not follow that P is true.

  1. We have evidence that P.
    Therefore,
  2. P.

This argument is also invalid, since the conclusion is not validly based on its premise. It remains possible that some new information will weaken the evidence and will fail to support the conclusion.

Hasty generalization

  1. I saw John eating pizza last Friday.
  2. I saw John eating pizza this Friday.
    Therefore,
  3. John eats pizza on Fridays.

Even though I saw John eating pizza on several occasions, it is a hasty generalization to assert that he eats pizza on Fridays. Drawing a general inference is just too strong for the specific evidence in hand.  

Conspiracy theory

  1. There is no evidence that P.
  2. No evidence is exactly what we should expect, if P is true.
    Therefore,
  3. P.

A conspiracy theorist believes that the conspiracy is so powerful that all evidence for its existence is carefully erased. So, an absence of evidence is exactly what the conspiracy theorist expects to find so that he or she could claim that the conspiracy exists. The more a belief looks false, the better its conspiracy claim to truth. A Conspiracy theory as fallacy is a strange twist on the Argument from Ignorance.

Argument from Authority

If a famous authority is cited in defence of some claim, an important step is to ask whether he or she is the proper sort of authority for the claim in question. The proper sort of authority is a person relative to a field. In other words, the person cited ought to have a recognized expertise on the particular topic. The fallacy of Argument from Authority is committed when the expert does not have appropriate educational background, work experience or lived experience for the claim in question. The authority cannot be grounded solely on the fact that the expert is great of famous in some other fields.   

  1. John said that P.
  2. John is a world-famous expert.
    Therefore,
  3. P.

Even though John is world-famous expert, he might have not any expertise in a claim in question. So, he is a false authority.   

Appeal to popular opinion

  1. It is widely believed that P.
    Therefore,
  2. P.

Fallacy of causal reasoning

  1. A happened before B happened.
    Therefore,
  2. A caused B.

This fallacy leads to massive over-attribution of causal connections where they do not exist. If something happened after a black cat crossed my path, it is not necessary that the cat caused it. Similarly, if something did not happen because I wore a good luck charm, it does mean that the charm has something to do with. 

Another fallacy of causal reasoning is sometimes called Law of similarity.

  1. A is similar to the effect B
    Therefore,
  2. A causes the effect B.

This kind of fallacy concludes that factors similar to some effect must have the power to cause the effect. For instance, in some alternative therapies, tusk powder is believed to have detoxifying properties, giving skin a luminous glow. It is also said to relieve osteoporosis and to help with excessive bone growth. However, there is no reason to think that if the tusk of an elephant resembles a smooth and shiny bone, it is disposed to be a cause for that resemblance.

Multiple endpoints

The fallacy of Multiple Endpoints is a way of misdiagnosing of correlations between objects, trends, or more abstract phenomena. This kind of fallacy is committed when we first gather data and then look for something surprising and significant. For example, if we decide to look for relational properties between two random persons, there will be a high probability that we will find some commonalities. “Oh, what an extraordinary coincidence! “– we could exclaim. Consider that these two persons can be identical in numerous ways: eye colour, favourite television show, religion, favourite food, number of spoken languages, place of birth etc. However, if we decide in advance what common properties we’re interested and then look for them, the outcome will be different.    

Red Herring

Red Herring fallacy attempts to mislead or distract from the relevant topic to another issue to which the person doing the redirecting can better respond. This kind of fallacy is widely used during political debates.

Example 1: We can talk about my supposed affairs all night, but what our society really wants to know is when will the government start reforms to overcome the crisis.

Example 2:  

– Did your foundation accept money from terror organizations?
– My foundation has done a lot of good for the world, including combating poverty and inequality.

Straw Man Fallacy

The Straw Man Fallacy substitutes a person’s actual position or argument with a distorted, exaggerated, or misrepresented version of the position of the argument.

Example: You argue that he should be sent to prison because of his corruption affairs. Maybe you should be brought before a judge as well!  Or haven’t you ever been involved in corruption?

Ad Hominem

Ad Hominem fallacy is about dismissing an argument on the basis of personal facts about the arguer. It does not matter if these facts are negative or positive.

Some of the examples are:

  • You are too young and innocent to understand it, so your argument does not work.
    or
  • You are silly, so your argument does not work.

Poisoning the Well

This kind of fallacy devaluates the view of the arguer and undermines the whole conversation.

Examples:

  • It does not matter what you are saying as you are conditioned to say that.
  • I was thinking the same way before this accident happened.
  • When you’re my age, you will do the same.

The Mrs. Lincoln Fallacy

It is a species of fallacy which ignores clearly relevant factors and treats subsequent inferences as significant:

  • Other than that … (any relevant factors), how was your … (insignificant factors)?

Begging the question

Begging the question is a form of a circular reasoning in which the conclusion is assumed true through the premise of the claim.

  1. John said that Pegasus exists.
  2. John has some reasons to believe that Pegasus exists.
    Therefore,
  3. It’s reasonable to believe that Pegasus exists.

This argument is not just valid, but even sound. However, it does not provide a logical or new conclusion based on the information within it.  Even though the form of circular reasoning is “P, therefore P”, it fails to provide a reason to believe its conclusion, irrespective of its validity of soundness. Asking for a justification of the premise will lead us in a circle.

  1. John said that Pegasus exists.
  2. It’s reasonable to believe that Pegasus exists.
    Therefore,
  3. John has some reasons to believe that Pegasus exists.

False presupposition

This fallacy is committed when an arguer includes in his or her statement a presupposition that may be false.

Examples:

  • Do not worry, I will not tell anyone that you steal money from the parents’ wallet.   (Presupposition: You are stealing money.)
  • Are you still friends with that loser John? (Presupposition: John is a loser)

No True Scot fallacy

This is a fallacy in which a claim is offered as an empirical truth and then is converted into an analytical definition that is always true.   

  • All true Scots eat oatmeal.
  • My uncle MacGregor is a Scotsman and he doesn’t eat oatmeal.
  • Well, then MacGregor is no true Scot!

“All true Scots eat oatmeal” is presented as an analytical definition that rules out counter-examples altogether, making the claim necessarily true.   

Fallacy of false dilemma

This is a fallacy that consists of the assumption that there are a limited number of options, when in fact there are more.

  1. Either we cut a defense funding this year or we live with a huge deficit. (P or Q)
  2. We can’t live with a huge deficit. (Not Q)
    Therefore,
  3. We’ll have to cut a defense funding.  (P)

Even though this argument is valid, it is not sound. The first disjunctive premise (P or Q) is false as there are other possibilities not expressed by P or Q.

Fallacy of composition and division

This fallacy consists of invalid inferences between a whole and its parts.

  1. The parts have property X.
    Therefore,
  2. The whole has property X.

By the same token,

  1. The whole has property X.
    Therefore,
  2. The parts have property X.

Naturalistic Fallacy

When somebody argues that something is valid and justified because it’s natural, he commits a naturalistic fallacy.

  • It’s natural to give to charity.

The naturalistic fallacy occurs in negated form as well. One might argue that something is unnatural to do.

  • It’s unnatural to kill. 

A conception of what’s natural or unnatural involves the basic notion of a “proper function”: what a system in nature is for. However, there are numerous examples in nature that are horrifying but functional. Animals killing other animals for genetic representation is totally natural, while sending financial aid for years to charities has not very clear analogue in nature.

The Gambler’s fallacy

The gambler’s fallacy is a reasoning of gamblers to think that there is a certain distribution of wins and losses over the long term in random events. For example, a gambler losing all night may think that he must be due to win. He supposes that the probability of the win of the last gambling is somehow dependent on the probability of the series of all past games. The probability that the gambler loses all 10 games is (1/2)10 = 1/1024.The fact that he loses 9 games does not affect the probability of the last game which is just an independent event with probability 1/2. 

Regression fallacy

When someone confuses a random effect with some correlation or causal trend, a regression fallacy is committed. It’s a sort of the fallacy of causal reasoning. Suppose that there is some extreme event after each there is not much room for a continuation of that effect. In this case, an extreme measurement will tend to be followed by a measurement that is closer to the mean. So, it would be fallacious to expect exceptional results to continue as if they were average. When results become normal after the peak, we believe that some action was the cause of that change when in fact it was not causal.

  • John behaved very badly. His parents punished him. John’s behaviour improved, so punishment is useful in education.
  • Alice behaved very well. Her parents rewarded her. Alice’s behaviour declined, which means that her parents spoiled Alice.

These reasonings are fallacious since exceptional behaviour of John and Alice are followed by more normal behaviour. For John, the change toward the average means improvement, while for Alice it means a regression.       

Appeal to emotion

Appeal to emotion is a fallacy that use emotion in place of reason to support a claim. In this case, the audience may jump directly to the desired conclusion without noticing the lack of reasonable grounds to believe it. 

  • Is John guilty of bank robbing? I hate bank robbers. They are immoral criminals. Don’t let John walk away from this crime.

Bibliography:

Kenyon, Tim, Clear Thinking in a Blurry World, Nelson Education Ltd, 2008.