19 - Fallacies
The word fallacy is broadly used to refer to a belief that is wrong (for whatever reason), but in terms of critical thinking it has a specific meaning: a fallacy is a mistake that violates the principles of correct reasoning. In that sense, a person can present factually accurate information, but still commit a fallacy.
In its strictest sense, fallacy is applied to the relationship between the premises and conclusion of a single argument - but because bad premises can lead to a bad conclusion, it is necessary to apply the notion of fallacy in a broader sense, to consider whether any given statement is fallacious.
Classifying Fallacies
There is no established and universal method of classifying fallacies -Aristotle in Greece and Xunzi in China classified them differently, and there are various ways of sorting them out. The author presents his own system, based on their nature:
- Inconsistency - The claim is self-defeating or inconsistent with other premises
- Inappropriate assumption - Something is assumed to be true (or relevant) without reason
- Irrelevance - Appealing to information that has no relevance to the argument
- Insufficiency - Accepting a conclusion with weak or missing evidence
The author has proposed this scheme because it is more intuitive. If you understand the reason a fallacy has occurred, you can then diagnose and identify it.
Fallacies of Inconsistency
A contradiction is a statement that negates itself - the statement "nothing is universal" is contradictory because the statement itself is meant to be taken as a universal. Not all contradictions are so obvious, and they often occur as a failure to clearly define premises, such that the conclusion seems "both right and wrong" because we haven't sorted out the conditions under which it is right or wrong.
A self-refuting claim is similar: if someone says "I do not speak any English" in English, then they do speak it (enough to say that sentence); or to say "I will not comment on my despicable wife" is to make a comment in the same sentence.
The single-sentence examples are a bit ludicrous and make it seem that contradiction would be rare - but it is a lot more common when two separate statements contradict one another. Not may people have examined their beliefs, and often hold contradictory ones that evidence themselves during the course of an argument.
Fallacies of Inappropriate Assumption
There are a number of fallacies that are based on an inappropriate assumption, or the presumption of truth that has not been established. Consider the following:
Circular Arguments
The statement that "we should study history because it is an important subject" provides no proof of its importance: we should study important subjects is one argument, history is an important subject is a second.
Many arguments involving religious premises become circular arguments because they assume something that an opponent is likely to deny. "It's true because it's in the Bible" carries no weight no someone who does not believe everything in the Bible to be true - and is based on the premise that it is.
False Dilemma
A false dilemma proposes a finite number of outcomes, assuming there to be no other possibility. The assertion "if you're not for us, you're against us" excludes the possibility that a person is not involved in the conflict at all.
The most common such dilemma is the question of whether something is "good or bad" without consideration of whether it may be neither good nor bad. There are many choices that are morally neutral under most circumstances.
Loaded Questions
In confrontational situations, people attempt to gain a point by trickery: "Did you wash your hands after killing your wife?" assumes that you killed your wife, and answering the question yes or no is taken as admission to the crime.
(EN: I'm familiar with the concept, but do not see the relevance to critical thinking. Looking to other sources, I really don't see it outside of political debate or courtroom drama - and as such I don't think it's a fallacy that might corrupt a person's critical thinking so much as an attempt to use wordplay to "prove" an argument that is known to be invalid.)
Fallacies of Irrelevance
Fallacies of irrelevance introduce information that has nothing to do with the subject of debate. The most common of these is the personal attack: "Only an idiot would believe that" does not address the argument at all. Race-baiting is a similar distraction - "only a racist would believe such a thing" is tossed out to distract from the argument and lead the other person to defend themselves on other grounds.
There are many related fallacies in which something is argued to be true based on an inappropriate appeal to something entirely irrelevant:
- Cannibalism is a tradition in our culture and it is wrong for outsiders to criticize it
- That politician is probably dishonest because his brother is a convicted criminal
- An esteemed professor said that it was true, so it must be
Appealing to tradition, association, or authority are not necessarily a fallacy - but they are not generally sufficient to prove a statement true without additional information.
Another source of an irrelevant statement is in assuming something unusual to be typical. "it must not be illegal to run a stop sign because I didn't get a ticket the last time I did so" assumes the traffic cops to be omnipresent (or even if there was one present, he wasn't paying attention).
Irrelevant responses are also common in argumentation when someone is attempting to cover up the truth with unrelated information. If a reporter asks if a police raid was authorized, the respondent may read a set of rules about when a raid is legally authorized without pointing out that the act in question did or did not meet those criteria. It is irrelevant because the reporter didn't ask what the rules were, but whether they were followed in a given instance.
A lot of advertising claims are likewise based on our susceptibility to irrelevant information. A product is called "fresh" but contains no fresh ingredients, a popular athlete is paid to endorse a product he does not use, a product that costs the same as its competitors claims to be a bargain, etc.
Fallacies of Insufficiency
A fallacy of insufficiency applies to an argument whose premises are too weak to support the conclusion, even though they are relevant.
Generalization is a common practice - using terms such as always/never or all/none when there is insufficient evidence. This is especially true when an unusual example is used to suggest something is true of the entire population (the fact that one graduate of a university won a Nobel prize is presented to suggest the quality of education). It is also true of statistics - the indication that 51% of people hold an opinion is meant to suggest it is true of "a majority", and then applied to all.
Consider the instances of medical misdiagnosis where the physician noticed few symptoms and jumped to a conclusion about their cause without doing a thorough examination of the patient. The same happens in argumentation with much greater frequency.
Insufficiency is also the key problem with weak analogies because they consider two items to be identical when they are only similar. What is true of cats is not true of horses simply because they are both domesticated quadrupeds - or to tap a hackneyed expression, what is true of apples is not true of oranges simply because they are both fruit.
A List of Fallacies
The author provides a list of common fallacies, which is far from comprehensive, but worth considering:
- Affirming the consequent - An error in the relationship between two phenomena. "Every time John eats, he sits at a table; therefore if he is sitting at a table, he is eating."
- Ad hominem (personal attack) - Attacking the person who made a statement rather than the validity of the statement. "George's theory is wrong because George is a Jew."
- Ad Ignoratum - Assuming that a theory is true because there is no evidence proving it is not. "Life must exists on other planets because we have not yet inspected every planet to prove it does not."
- Ad misericordiam - Invoking emotion, or he prospect of emotion to circumvent logic. "How would you feel if someone did that to you" does not mean that it is not logical or justified to do something.
- Ad populum - Suggesting that a theory is plausible because it is accepted by a lot of people. "A lot of people believe that sugar cures cancer" does not make it true.
- Begging the question - Using loaded terms in a premise. "Abortion is wrong because it is murder" is a tautology because murder is defined as a wrongful killing.
- Sample bias - asking a question of a group of people who are inclined to give a certain answer. If you poll people exiting a church as to whether they believe in God, you will find that 80% or more of them do - but this is not true of the whole population.
- Complex/Loaded question - proposes a question that presupposes facts. "Do you still beat your wife" implies the certainty of a past behavior that is not proven.
- Composition/Division - Assuming the whole contains the same properties as each of its parts or vice-versa. Sodium is toxic and chlorine is toxic, therefore sodium chloride (table salt) must be toxic ... or since sodium chloride is not toxic, neither sodium nor chlorine must be toxic.
- Equivocation - Switching the meaning of a term in an argument: "a feather is light, therefore it cannot be dark" changes the meaning from weight to color. It's very common in politics with concepts like "equality"
- Etymological fallacy - Insisting that the original meaning of a word, or its meaning in it s language of origin, represents its real meaning. Because "malaria" is derived from ma (bad) aria (air), it must be caused by bad air.
- False Dilemma - Suggesting that a limited number of outcomes (generally two) is exhaustive and ignoring or denying other possibilities. "You love it or you hate it" denies an entire range of emotions in-between, as well as indifference, as well as loving it in some regards while hating it in others.
- Gambler's Fallacy - Believing that two or more events that do not influence each other are in fact related.
- Genetic Fallacy - The believe that if X "comes from" Y it must have the same properties. This is most often used to suggest that a son has the same character as his farther, or believing an idea has no merit because it came from a disreputable person.
- Hasty Generalization - A decision that something must be true of a population based on limited experience. A woman concludes "all men are pigs" after two or three bad relationships.
- Non Sequitur - An argument in which the premises have nothing to do with the conclusion. "Jack must be an excellent plumber because he has red hair."
- Post hoc ergo propter hoc - A suggestion that because one event followed another is sufficient evidence that there is causation.
- Red herring - An issue irrelevant to an argument that is intended to spawn a different discussion and distract from the main argument. To suggest that eating animals is cruel in an argument over whether eating meat is healthy is unrelated.
- Slippery Slope - A suggestion that the acceptance of a conclusion means that an additional conclusion is inevitable. "If you take cocaine at a party, you will become an addict, and then steal to support your habit."
- Straw Man - Suggesting an argument for the opposing side that can be easily defeated, to preempt them from presenting their actual argument, which is more difficult to address.
- Two Wrongs - An argument that two wrong things cancel or balance one another. For example, proposing that is permissible to steal from a thief.
- Wishful thinking - Believing something to be true simply because it is pleasant, or would be unpleasant to think otherwise. We might agree that the idea of an afterlife is more appealing that merely ceasing to exist, but that doesn't make it true.
- Weak analogy - Drawing a comparison between two things that are similar in a few inessential aspects but also have significant dissimilarities. "Eating salt is like taking poison" is obviously ignoring tremendous differences in scale between their harmful effects.