What is Fallacious Reasoning?

To define a fallacy, first note that when someone is making an argument, it is important for that argument to be based on logic. When the logic of an argument is flawed, it is referred to as fallacious reasoning. Specific types of errors that can occur in logic are referred to as logical fallacies. Although fallacious reasoning may initially seem sound, examining it more closely reveals that there is a problem with either an underlying premise or a conclusion that has been reached. When an argument is logical, the premise, or underlying idea, leads naturally to the conclusion, or result, of that premise. Although an argument based on a logical fallacy may be convincing, it might mislead or confuse the reader and can undermine the writer’s credibility. There are many types of logical fallacies but three of the most common are either/or, generalization, and non sequitur.

Either/Or

An either/or fallacy is essentially a false choice. In other words, if a person is making an argument and pretends that a scenario only includes two options when there are, in fact, many potential options, this is an either/or fallacy. Imagine that a parent is trying to convince their child that attending college is important and makes the following statement.

“You can either go to college or work a low-wage job for the rest of your life.”

The parent is basing the argument on the idea that there are only two possible options for the child’s future: attend college or make low wages. In reality, there are many possible outcomes. The child might

• enroll in a trade school instead of a college and train for a high-paying position.
• begin working in a low-wage position and then advance to become a supervisor or manager.
• attend college but ultimately take a job unrelated to their degree.
• attend college and work in a low-paying position that aligns with their degree.

Although the options presented in the original argument may occur, any one of these additional options could also prove true. To ignore the possibility of them is an either/or fallacy.

Generalization

Another form of fallacious reasoning is generalization. Unfortunately, generalizations are commonly used and often accepted within arguments, but they are nevertheless problematic. A generalization occurs when a conclusion is based on insufficient evidence. In research, this can occur if a study uses a sample size that is too small. In day-to-day life, people frequently resort to generalizations, assuming that what is true of one particular member of a group must be true of the entire group. While the origin of the argument may be based on a grain of truth, when it is unfairly applied based on limited evidence, it becomes an overly broad generalization. Consider the statements below.

1. The meal I ordered at this restaurant tastes terrible, so all of their food must be bad.
2. Lucas, who is Australian, stole my wallet; therefore, all Australians are thieves.
3. The first day of this job has been boring, which means that every day at work will be the same way.

Each of these examples is based on a generalization that has been unfairly and illogically applied. If a person made any one of these arguments, someone could easily refute or disprove it by illuminating the lacking evidence and other possible conclusions. The responses below could easily be applied to disprove each of the arguments above.

1. The fact that one meal is bad does not indicate that this is true of all of the food. Perhaps the chef made a mistake with this specific meal or it simply wasn’t to the taste of the diner. A single meal is not representative of every kind of food that the restaurant serves.
2. Although Lucas is clearly a thief, he is only one person amongst millions of Australians. It is ridiculous to assume that the behavior of the entire population would be the same as this one man.
3. It is possible that the job will always be boring, but a single day is not sufficient evidence to draw this conclusion. The first day, by nature, may include paperwork, tasks, and training that subsequent days would not include.

Basing an argument on a generalization is often seen as careless, thoughtless, or even offensive, and it should always be avoided.

Non Sequitur

The term non sequitur is Latin and translates to “it does not follow.” It was adopted into the English language in the 1500s to describe a situation in which a conclusion does not logically follow a conclusion. Since then, it has evolved to encompass a broader range of statements. In modern usage, a non sequitur is any situation in which a response to another person’s statement seems completely irrelevant or unrelated to the original topic. For example, if Susan says, “I want to see this movie,” and her friend replies, “I wish I had some coffee,” this is a non sequitur.

In some situations, a non sequitur may be complex. Consider the example below.

“All singers are happy people. Martha is always happy. Therefore, Martha must be a singer.”

The logic in this argument is flawed in multiple ways. After all, some of history’s greatest music may never have been created if all singers were happy. More importantly, even if the second premise were true and all singers were, in fact, happy people, it does not logically follow that Martha is a singer. She could be any number of things, such as a teacher, plumber, or firefighter, and be a happy person. It is not logical to make a conclusion about her emotional wellbeing or state of mind based simply on her hobby or profession.

Other non sequitur statements may be more readily apparent. If someone says, “Adam loves traveling. He is having pizza for dinner,” this is clearly a non sequitur because the second statement does not seem relevant to the first. There may be some underlying connection between the two statements, but it has not been articulated by the speaker. For example, maybe the speaker thought about Adam traveling to Italy and this inspired the comment about his dinner plans. However, unless this connection is directly stated, the result is a non sequitur.

Identifying Logical Fallacies

Logical fallacies are used so commonly that at times it can be difficult to detect them. Asking questions about the foundation of an argument can help to determine whether the reasoning is sound or fallacious. To identify these particular fallacies, consider the questions below.

1. Are there other possible options that the argument ignores? If so, this is an either/or fallacy.
2. Is there sufficient evidence to prove that this conclusion is true? If not, this is a generalization.
3. Is there a clear connection between the statements, or the premises and conclusion, in the argument? If not, this is a non sequitur.

Applying each of these questions to individual arguments helps to reveal whether they are based on logic or if the reasoning is flawed. Consider the examples below.

1. Today, Sylvia moved in with a new roommate who was coughing and appeared to be sick. Her new roommate must have chronic health problems.
2. Isabelle got sick the last time she ate at this restaurant, so she would prefer not to eat there again.
3. When choosing a career, one must focus on either happiness or financial stability; it is not possible to have both.
4. In a survey of eight hundred local high school students, seventy-five percent said that they would prefer to have less homework. Thus, there is good reason to consider a reduction of the homework load in the local high schools.
5. John grew up with many different pets. He wants to be a police officer.

Of these statements, only two and four are logical. The others have logical fallacies.

• “Today, Sylvia moved in with a new roommate, who was coughing and appeared to be sick. Her new roommate must have chronic health problems.” There is limited evidence to prove that Sylvia’s new roommate has chronic health problems because they have known each other for less than a day. Therefore, this is a generalization.
• “When choosing a career, one must focus on either happiness or financial stability; it is not possible to have both.” This is an either/or fallacy because the argument has reduced the number of options to only two when others exist. For example, some people are able to work in jobs that make them both happy and financially secure, but the argument ignores this possibility.
• “John grew up with many different pets. He wants to be a police officer.” There is no logical connection between these two statements; if John had a lot of pets, it does not follow that he wants to be a police officer. This is a non sequitur.

Lesson Summary

Effective arguments should be based on sound logic. An argument with flawed logic is referred to as fallacious reasoning and may include any number of logical fallacies or specific errors in logic. Fallacious reasoning can undermine someone’s credibility, confuse or mislead the reader, and make the argument easy to disprove.

The either/or fallacy refers to a situation in which the argument has reduced a scenario to only two possible choices, a false choice, when in fact other options exist. A generalization occurs when there is insufficient evidence to reach a conclusion, such as when a trait that is true of a single member of a group is applied to the entire group. A non sequitur, which translates to “it does not follow,” is when the connections between two statements are not clear, meaning that one does not logically follow the other. It can be challenging to identify fallacious reasoning, but asking questions about the underlying logic of a statement, including the premise and conclusion, can help reveal any existing fallacies.