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Recall that philosophers understand what they do as presenting and analyzing arguments in order to come to an understanding of the topics being discussed. To a philosopher, an argument is not a disagreement between people but a series of statements intended to establish the truth of a position. These statements are called propositions and can be premises (a proposition intended to give evidence for another claim) or a conclusion (a proposition intended to capture the judgment or decision from the reasoning process).
Some arguments are done quite systematically and use strict rules of what can be done with the existing premises. These arguments can be understood as similar to the proofs that are done in geometry. These systematic arguments are looking for validity—or a certainty that if the premises are true, the conclusion must be true. Validity is a measure of the structure of the argument. When an argument is valid if the premises are true, then the argument is considered sound, and the conclusion must be true in practice, not just in theory.
In contrast to deductive arguments that follow standards that limit what can be derived, most of the arguments that we encounter in our daily lives are inductive arguments. These arguments still have premises and conclusions, but there is no attempt to get certainty from the argument. Instead, these inductive arguments are understood as being stronger or weaker than other arguments. The vast majority of arguments that one encounters in letters to the editor, blog posts, social media threads, or in a conversation between friends are like this: their purpose is persuasion, not definitive proof.
An error in reasoning, whether in a deductive or inductive argument, is called a fallacy. The fallacies for deductive arguments are errors in the structure of the argument that prevent it from being valid. The fallacies in inductive arguments are not about the structure but instead about the content of propositions. It is this second grouping—the informal fallacies—that we will be focusing on here.
Reasoning can go wrong in many ways. When the structural form of an argument is problematic, it is called a formal fallacy. Mistakes in reasoning are not usually caused by the structure of the argument. Rather, there is usually a problem in the relationship between the evidence given in the premises and the conclusion.
EXAMPLE
I don’t think Ms. Timmons will make a good mayor. I’ve got a bad feeling about her. And I’ve heard she’s not a Christian. Furthermore, the last time we had a female mayor, the city nearly went bankrupt. Don’t vote for Ms. Timmons.Notice that to assess the above argument, you must think about whether the reasons offered function as evidence for the conclusion that Ms. Timmons would be a bad mayor. This assessment requires background knowledge about the world. Does belonging to a specific religion have any bearing on one’s qualification for mayor? Is there any credible connection between a mayor’s gender and the likelihood that the person will cause a bankruptcy? If the reasons are not adequate support for the conclusion, then the reasoner commits an informal fallacy. In this argument, none of the reasons offered support the conclusion.
There are many specific types of informal fallacies, but most can be sorted into four general categories according to how the reasoning fails. These categories show how reasoning can go wrong and serve as warnings for what to watch out for in arguments. They are fallacies of relevance, fallacies of weak induction, fallacies of unwarranted assumption, and fallacies of diversion. Let’s look closer at each one.
In fallacies of relevance, the arguer presents evidence that is not relevant to logically establishing their conclusion. The reason why fallacies of relevance stick around is that the evidence seems relevant, meaning it feels real. Fallacies of relevance prey on our likes and dislikes. Indeed, the very first fallacy of relevance is called an appeal to emotion.
An appeal to emotion can target any number of emotions, from fear to pity and from love and compassion to hate and aversion. For the most part, appeals to emotion of any kind are not relevant for establishing the conclusion.
The ad hominem attack is most often committed by a person who is arguing against some other person’s position. “Ad hominem” in Latin means “toward the man.” It is so named because when someone commits this fallacy, the reasons they give for their conclusion concern the characteristics of the person they are arguing against rather than that person’s position. The arguer may verbally attack the person by making fun of their appearance, intelligence, or character; they can highlight something about the person’s circumstances, such as their job or past; or they can insinuate that the person is a hypocrite.
You may wonder why such arguments are effective. One reason is sloppy associative reasoning, wherein we problematically assume that characteristics held by an arguer will be transferred to their argument. Another related reason is that too often we allow ourselves to be ruled by emotion rather than reason. If we are made to feel negatively toward a person, those feelings can cloud our assessment of their arguments.
The fallacies of weak induction are mistakes in reasoning in which a person’s evidence or reasons are too weak to firmly establish a conclusion. The reasoner uses relevant premises, but the evidence contained therein is weak or defective in some way. These errors are errors of induction. When we inductively reason, we gather evidence using our experience in the world and draw conclusions based on that experience.
In such cases, the reasoner uses induction properly by using relevant evidence, but their evidence is simply too weak to support the generalization they make. An inductive inference may also be weak because it too narrowly focuses on one type of evidence, or the inference may apply to a generalization in the wrong way.
A hasty generalization is a fallacy of weak induction in which a person draws a conclusion using too little evidence to support the conclusion.
EXAMPLE
Sixty-five percent of a random poll of 50 registered voters in the state said they would vote for the amendment. We conclude that the state amendment will pass.Fifty voters is not a large enough sample size to draw predictive conclusions about an election. So to say the amendment will pass based on such limited evidence is a hasty generalization. Just how much evidence we need to support a generalization depends on the conclusion being made. If we already have good reason to believe that the class of entities that is the subject of our generalization is all very similar, then we will not need a very large sample size to make a reliable generalization.
EXAMPLE
Physics tells us that electrons are very similar, so a study drawn from observing just a few electrons may be reasonable. Humans (particularly their political beliefs and behaviors) are not the same, so a much larger sample size is needed to determine political behavior.The fallacy of hasty generalization highlights the empirical nature of induction. We need a basic understanding of the world to know exactly how much evidence is needed to support many of our claims.
A biased sample fallacy has some things in common with a hasty generalization. Consider the following.
EXAMPLE
Don’t eat dinner at that restaurant. It’s bad. My book club has met there once a week for breakfast for the past year, and they overcook their eggs.This seems much better than the restaurant example offered above. If the book club has gone to the restaurant once per week for a year, the arguer has more than 50 instances of data. However, notice that the arguer’s evidence concerns breakfast, not dinner, and focuses on the eggs. Suppose the restaurant has an entirely different, more extensive dinner menu; then we cannot draw reliable conclusions about the restaurant’s success at dinner. This is an example of a biased sample. With a hasty generalization, the problem is that not enough evidence is used. In a biased sample, the problem is that the evidence used is biased in some way.
Appeal to ignorance is another type of fallacy of weak induction. Consider the following line of reasoning.
EXAMPLE
In my philosophy class, we reviewed all the traditional arguments for the existence of God. All of them have problems. Because no one can prove that God exists, we can only conclude that God doesn’t exist.Notice that the arguer wants to conclude that because we do not have evidence or sufficient arguments for God’s existence, then God cannot exist. In an appeal to ignorance, the reasoner relies on the lack of knowledge or evidence for a thing (our ignorance of it) to draw a definite conclusion about that thing. However, in many cases, this simply does not work. The same reasoning can be used to assert that God must exist. Any form of reasoning that allows you to draw contradictory conclusions ought to be suspected. Appeals to ignorance ignore the idea that the absence of evidence is not evidence of absence. The fact that we lack evidence for X should not always function as evidence that X is false or does not exist.
The fallacy of false cause occurs when a causal relation is assumed to exist between two events or things when it is unlikely that such a causal relationship exists. People often make this mistake when the two events occur together. The phrase “correlation does not equal causation” captures a common critique of this form of false cause reasoning.
EXAMPLE
A person may think that swimsuits cause sunburns because people often get sunburned when wearing swimsuits. There is a correlation between sunburn and swimsuits, but the suits are not a cause of sunburns.False cause fallacies also occur when a person believes that just because one event occurs after another, the first event is the cause of the second one. This poor form of reasoning, in tandem with confirmation bias, leads to many superstitious beliefs. Confirmation bias is the natural tendency to look for, interpret, or recall information that confirms already-established beliefs or values.
Fallacies of unwarranted assumption occur when an argument relies on a piece of information or belief that requires further justification. The category gets its name from the fact that a person assumes something unwarranted to draw their conclusion. Often, the unjustified assumption is only implicit, which can make these types of fallacies difficult to identify.
False dichotomy, or “false dilemma,” occurs in an argument when a limited number of possibilities are assumed to be the only available options. In the classic variation, the arguer offers two possibilities, shows that one cannot be true, and then deduces that the other possibility must be true. Here is the form:
False dichotomy is poor reasoning because it artificially limits the available options and then uses this artificial limitation to attempt to prove some conclusion. A false dichotomy may include more than two options. The important thing to remember is that a false dichotomy limits options in an argument without justification when there is reason to think there are more options.
Begging the question occurs when an arguer either assumes the truth of the conclusion they aim to prove in the course of trying to prove it or when an arguer assumes the truth of a contentious claim in their argument. When the former happens, it is sometimes called circular reasoning.
EXAMPLE
The problematic assumption occurs in Premise 2. To say the Bible is “divinely inspired” is to say that it is the word of God. However, the argument aims to prove that God exists. So, Premise 2 assumes that God exists to prove God exists. This is patently circular reasoning. The name “begging the question” is confusing to some students. One way to think about this fallacy is that the question is whatever is at issue in a debate or argument. Here, the question is “Does God exist?” To “beg” the question means to assume you already know the answer. The argument provided assumes the answer to the question it is supposed to answer.
A word of caution is useful here: The phrase “begs the question” is often used, incorrectly, as meaning something like “automatically raises the question.” This increasingly common misuse of the phrase can cause confusion between those who use it in the logical sense and those who use it in the colloquial sense.
The final class of informal fallacies is the fallacy of diversion, which usually occurs in contexts where there is an opponent or an audience. In this instance, the arguer attempts to distract the attention of the audience away from the argument at hand. Clearly, the tactic of diverting attention implies that there is someone whose attention can be diverted: either an audience, an opponent, or both.
A strawman argument occurs when an arguer presents a weaker version of the position they are arguing against to make the position easier to defeat. The arguer takes their opponent’s argument, repackages it, and defeats this new version of the argument rather than their opponent’s actual position. If the audience listening to or reading the argument is not careful, they won’t notice this move and believe that the opponent’s original position has been defeated. Usually, when a strawman is created, the misrepresented position is made more extreme.
A red herring fallacy is like a strawman, except the arguer completely ignores their opponent’s position and simply changes the subject. The arguer diverts the attention of the audience to a new subject. A red herring is a smelly, smoked fish that was used to distract hunting dogs by dragging the fish along a path. The dogs would lose the scent that they were tracking because of the distraction of the malodorous fish. So, the fallacy gets its name because it means to trick people into following a different path of reasoning than the one at hand. You may wonder how a person can get away with simply changing the subject. Successful use of the red herring usually involves shifting the subject to something tangentially related.
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