In the previous chapter, you learned about the meaning and structure of argument and how to select high-quality evidence in order to build strong, valid arguments. In this chapter, we continue our exploration of argument by more broadly considering how arguments function. We do this by examining two interrelated concepts: patterns of reasoning and reasoning fallacies.

This chapter begins by explaining both terms and their relationship. We will next explain five patterns of reasoning and their related fallacies. The chapter will end by introducing you to a few additional fallacies.

Reasoning Patterns and Fallacies

When developing arguments in a speech, you can choose from several available approaches or patterns of reasoning. A reasoning pattern is derived from what kind of data or evidence is selected and how that data or evidence is used to prove a claim.

Generally, patterns of reasoning reflect the practice of inductive reasoning, a form of reasoning in which a speaker uses a series of examples, instances, or cases to support the likelihood of a conclusion. Inductive arguments are judged based on the strengths (or weaknesses) of the observational data offered in support of a claim. For example, an inductive argument might be based on a series of examples (the most common form of inductive reasoning), analogies, or even signs that collectively suggest the likelihood of a particular conclusion.

Working in concert with reasoning patterns is attention to reasoning fallacies. A reasoning fallacy refers to a flaw or defect in reasoning that undermines argument validity. A fallacy:

We will next introduce you to several reasoning patterns and their corresponding reasoning fallacies.

Types of Reasoning Patterns and Related Fallacies

This section will introduce you to five patterns of reasoning: reasoning from example, reasoning from analogy, reasoning from cause, reasoning from sign, and reasoning from authority. It will also consider how these patterns are sometimes used ineffectively, resulting in reasoning fallacies.

Reasoning from Example

The first type of evidence we discussed in chapter 26 was examples. The effort to prove a claim through examples, also understood as inductive reasoning, is called reasoning from example or generalization. That chapter’s discussion of examples as evidence identified several ways to evaluate reasoning from example.

• If an example passes those tests and there are a sufficient number of examples to prove the claim, then you can reasonably conclude that you have presented a valid argument (or at least that this portion of your argument is valid).
• If, however, the example(s) violates those conditions, it isn’t representative of the larger situation, or an insufficient number is presented, then a reasoning fallacy has been committed. This reasoning fallacy is known as a hasty generalization.

Box 27.1 Reasoning from Example: Sample Arguments

Consider reasoning from example through these two brief arguments:

Example 1: President Donald Trump’s inaccurate claim that the malaria drug hydroxychloroquine could be used to effectively treat COVID-19 proves that all presidents mislead the public.

Analysis: Is this example representative? Are there a sufficient number of examples to prove the claim that “all presidents mislead the public”? Is there enough detail to make this example believable or to prove the president made misleading statements? While one can always ask a variety of questions about an argument, this singular, brief example is insufficient to prove that all presidents mislead the public. This is an example, then, of a hasty generalization.

Example 2: President Trump’s inaccurate claim that hydroxychloroquine could effectively treat COVID-19, President Obama’s broken promise that people could maintain their existing health care plans under the Affordable Care Act, President George W. Bush’s administration’s inaccurate claims about Iraq possessing weapons of mass destruction, and President Clinton’s denial of a relationship with White House intern Monica Lewinsky prove that all recent presidents have misled the country in public statements.

Analysis: While certainly one could challenge the lack of detail in explaining the individual situations, overall, this argument is stronger. Rather than presenting only one example, four examples are offered, which would seem to be a sufficient number. By limiting or qualifying the claim to “recent” presidents instead of making a claim about all presidents, this argument is initially of sufficient strength to avoid being considered a fallacy.

Reasoning from Analogy

A second common form of argument is to reason from analogy. When using reasoning from analogy, also known as analogical reasoning, you attempt to prove a claim by comparing two situations or cases.

Box 27.2 Reasoning from Analogy: Sample Argument

In June 2024 when Dr. Vivek H. Murthy, then–surgeon general of the United States, advanced the claim, “It is time to require a surgeon general’s warning label on social media platforms, stating that social media is associated with significant mental health harms for adolescents,” he supported his argument through analogical reasoning:

Faced with high levels of car-accident-related deaths in the mid- to late 20th century, lawmakers successfully demanded seatbelts, airbags, crash testing and a host of other measures that ultimately made cars safer. This January the F.A.A. grounded about 170 planes when a door plug came off one Boeing 737 Max 9 while the plane was in the air. And the following month, a massive recall of dairy products was conducted because of a listeria contamination that claimed two lives.^[1]

Analysis: In this statement, Dr. Murthy demonstrates the principle of analogical reasoning. He asked readers and, ultimately, Congress to support issuance of a surgeon general’s warning label on social media platforms on the basis that the harms being caused by social media were analogous to the level of harm that justified actions and regulations to protect safety in other instances. He reasonably compared a new situation (regulation of social media) with past situations where regulations were used to address public problems (seat belts, airline safety, product food safety).

In testing analogies, speakers and listeners need to examine the similarities and differences between the implicated circumstances. In doing so, you might ask,

• Are the situations reasonably comparable?
• Do the situations possess more similarities than differences?

If you answer yes to these questions, then you should feel comfortable with the analogy. If, however, you find that the answer to both is no, then you have discovered a fallacy known as a faulty analogy or faulty comparison.

Reasoning from Cause

Another popular pattern of reasoning is reasoning from cause. Also known as causal reasoning, reasoning from cause is used when a speaker claims an event is caused by a particular circumstance or action. When a direct link between an action and a consequence is exhibited, then a causal argument can be very effective.

In determining whether a causal argument is valid, consider the following criteria:

• Does the fact that the effect has occurred after the cause reasonably signify a relationship between the two events?
• Are there important alternative reasons or causes that have been ignored?

When a speaker is guilty of attributing a cause-effect relationship between two items that are not connected, they have created a faulty cause fallacy. When the faulty attribution of cause occurs only after the fact (e.g., in hindsight), the reasoning error is more specifically known as a post hoc fallacy.

Box 27.5 Post Hoc Fallacy: Sample Argument

Consider the following example heard from a discouraged New York Mets fan: “I never watch the Mets on television because they always lose when I do.” If we call back to the Toulmin model (in the previous chapter), we can pinpoint that the reasoning flaw in this causal argument rests in the implied warrant: “What I do determines whether the Mets win or lose.”

Analysis: There might be a miraculous coincidence between this fan’s viewing habits and their favorite team’s results, but in reality we know there is no causal connection between the two. Hence this beleaguered fan has (knowingly, no doubt) created a faulty cause fallacy of the post hoc variety.

Slippery Slope Fallacy

Relatedly, speakers sometimes attempt to use causal reasoning to argue that a single event or action will lead to a chain reaction of cause-and-effect events, typically ending with a catastrophic outcome. To effectively make such an argument, the speaker would need a significant amount of evidence to support the idea that one cause-and-effect sequence will lead to another, then to another, and to another. When speakers advance such arguments without providing necessary support, they commit a fallacy known as a slippery slope. They suggest that if a first step is taken, then we will slide all the way down the slope to the very bottom.

Reasoning from Sign

Reasoning from sign relies on circumstantial evidence, or signs, to demonstrate a claim.

For instance, a driver might notice a dashboard warning light indicator and say, “There must be something wrong with my car. The check engine light is on.” They have made a sign argument:

• Their claim (“There must be something wrong with my car”) is based on
• sign data (“The check engine light is on”).
• The implied warrant to the argument is that “vehicle warning lights signal a possible problem.” The warning light indicates to the driver that the car should be checked by a mechanic.

Note, however, that the engine light is not the cause of the problem, nor is it the problem itself; it is only a sign, or indicator, of it.

It is important to note, however, that it is possible to commit the mistake of misreading a sign. This happens when one assumes that a certain sign is a reliable indicator of something else when it is not.

Box 27.7 Misreading Signs: Sample Argument

In the wake of the 2012 shooting death of Trayvon Martin, there was a national debate over the meaning of his clothing—a hoodie—and if it could be reasonably interpreted by George Zimmerman, who killed Martin, as a sign of Martin being a threat or a gang member. The hoodie became a prominent part of national discussion, an exhibit in the criminal trial, and part of an exhibition on post–Civil War Reconstruction at the National Museum of African American History and Culture.^[3]

Analysis: Making faulty associations between circumstances (Martin’s sweatshirt) and an outcome (Zimmerman’s assumption of Martin’s intent to harm him) is what we mean by “misreading signs.”

Thus, in considering a sign argument, you should scrutinize the connection being made between the claim and the data.

• If the sign evidence is an accurate referent or indicator and/or if you can expect that the events reasonably occur together (but one does not cause the other), then you have a valid basis for a sign argument.
• If the sign is an unreliable indicator or referent and/or if you cannot reasonably associate events to occur together, then you are in danger of misreading a sign.

Reasoning from Authority

A final reasoning pattern is reasoning from authority. Reasoning from authority occurs when a speaker supports a claim with the testimony or credibility of a qualified source. The use of authority is common in argumentation.

Box 27.8 Appeal to Authority: Sample Argument

In a June 2024 essay in The Wall Street Journal, Gerald F. Seib argued the perils of mounting debt to the continued prosperity of the “American Empire.” Seib based his argument on the authority of scholars who had studied the impact of debt on past civilizations:

• He quoted historian Niall Ferguson on lessons offered by Habsburg Spain, France, the Ottoman Empire, and the British Empire.
• He drew on the analysis of J. H. Cullum Clark, director of the George W. Bush Institute-Southern Methodist University Economic Growth Initiative, in his study of the spending of the Roman Empire.
• He recounted the lessons of Yale historian Paul Kennedy’s well-known The Rise and Fall of Great Powers.

Analysis: In each case, Seib used the subject authority of public intellectuals as support for his argument on the threat posed by growing debt.^[4]

In the last chapter’s discussions of testimony, we considered several ways to evaluate reasoning from authority. The use of authority must pass those tests for the argument to be valid:

• The source is a qualified authority due to their subject expertise, societal position, or special circumstances.
• The source has firsthand knowledge of the issue without undue bias.
• The source’s assumptions match your own.

When a source of authority does not pass these tests, then basing a conclusion on evidence from that source can produce an appeal to authority fallacy.

Box 27.9 Appeal to Authority Fallacy: Sample Argument

When Dr. Robert Jarvik promoted the popular cholesterol drug Lipitor in a national television campaign, parent company Pfizer and Dr. Jarvik were questioned over the use of Jarvik’s authority. In the commercial, Jarvik is accurately credited as the inventor of the artificial heart and is ostensibly shown rowing across a body of water. Jarvik goes on to speak about the wonder of the heart and the risks associated with excess cholesterol while verbally and visually offering an argument from authority:

Claim: “When diet and exercise aren’t enough, adding Lipitor significantly lowers cholesterol.”

Data: Jarvik’s endorsement of the drug, and his performance of the physical activity of rowing.

Warrant: [Implied] If Dr. Jarvik, a heart expert, trusts the drug, I should too.

Analysis: The argument would seem to be a reasonable one at the surface—a nationally renowned doctor who has studied the heart endorses a drug as improving health. However, Dr. Jarvik is a medical researcher rather than a cardiologist, and he is not licensed to practice medicine or prescribe medication. Furthermore, it turns out Jarvik doesn’t row, and the commercial featured a body double to simulate his physical activity. On the whole, the commercial reflects an appeal to authority fallacy for how it used Jarvik, something that eventually caught the attention of Congress and resulted in Pfizer ending the campaign.^[5]

A sharp understanding of reasoning patterns can help you participate more effectively in the civic realm. Using a variety of reasoning patterns can enhance your ability to convince an audience to accept your thesis.

• For example, suppose you discover that your entire speech is based on sign argument. That means you have relied extensively on circumstantial evidence, and it is likely there is a lot of statistical data throughout the speech.
• It might be helpful to balance the speech by including reasoning from authority through the use of testimony—to add a human dimension and gain source credibility—as well as an example or two to which an audience can relate (reasoning from example or reasoning from analogy).

Such balancing creates stronger arguments by broadening the speech’s overall appeal to your community.

Box 27.10 Reasoning Patterns and Associated Reasoning Fallacies

Additional Common Fallacies

Although you can find many more examples of fallacy types in argumentation and logic courses, we limit our further consideration of the topic to five additional common fallacies: appeal to popularity, appeal to common practice, begging the question, ad hominem attack, and false dilemma.^[6]

Appeal to Popularity

Do you remember your parent asking, “If everyone else jumped off a bridge, would you do it too?” This was their way of introducing you to the appeal to popularity fallacy, even if they didn’t identify it as such. The basic idea is that popularity alone doesn’t make for a good argument.

Example: The success of Barbie as the top-grossing movie of 2023 proves that it was the best film from that year.

Analysis: The only basis this argument offers for being “best” is popularity. That might be one relevant piece of data. Basing the claim only on popularity, however, commits a fallacy, because it equates popularity with being the best.

Appeal to Common Practice

This fallacy is also called an “is/ought” fallacy because the speaker suggests that just because something is a certain way, it ought to be that way. Whereas an appeal to popularity relies on people’s positive feelings about, or approval of, a statement or activity, an appeal to common practice relies on the commonality or tradition of the belief or activity as justification for its validity.

Example: I know many professors look down on using ChatGPT to help write essays, but most students use it, so it must be OK.

Analysis: The only justification offered for the action (use of ChatGPT) is its asserted status as a common habit of students. However, as explored in chapter 5’s discussion of ethics, original work and the ability to understand the principles of speechmaking are important expectations for learning and operating professionally.

Begging the Question

When begging the question, the speaker fails to provide evidence for their claim and, instead, restates the claim in place of additional data. This fallacy is also known as circular reasoning.

Example: Reading is fundamental to a good education because an educated person needs to be able to read.

Analysis: In this example the claim (reading is fundamental to a good education) and data (an educated person needs to be able to read) are nearly identical, with no offer of proof or independent support beyond a slight restatement of the claim.

Ad Hominem Attack

An ad hominem fallacy occurs when the person, rather than the argument, is attacked. Certainly, on occasion, character is an issue in an argument, and in those cases questioning a person’s character is not a basis for deeming an argument fallacious. However, when the substance of a disagreement is ignored in favor of a blatant attack, an ad hominem fallacy has been committed.

Box 27.11 Ad Hominem Fallacy: Sample Argument

Consider this exchange between two congressional representatives during contempt proceedings against Attorney General Merrick Garland in May 2024.

Example: “I don’t think you know what you’re here for.…I think your fake eyelashes are messing up what you’re reading”—Georgia Republican Congresswoman Marjorie Taylor Greene to Texas Democratic Congresswoman Jasmine Crockett during a House oversight meeting on May 16, 2024.

Response: “I’m just curious…if someone on this committee then starts talking about somebody’s bleach blonde, bad built, butch body, that would not be engaging in personalities, correct?”—Jasmine Crockett, in response to the suggestion that Marjorie Taylor Greene’s comment was not about personal characteristics and appearance.

Analysis: In these examples, Greene and Crockett trade physical insults rather than discuss the substance of their differing views. Such comments do not advance argumentation, and they distract from argumentation by engaging in personal attacks.^[7]

False Dilemma

You have probably heard a variation of the phrase “You’re either with us or against us.” This familiar ultimatum, like all false dilemmas, eliminates alternative options by suggesting there are only two conclusions available when additional possibilities exist. It is possible to side “with us” but be “against” particular ideas or tactics.

Example: We must either ban all cars immediately to stop pollution or accept that the planet will be destroyed by climate change.

Analysis: The statement suggests only two possible outcomes—banning cars or planetary destruction—while ignoring other potential solutions related to electric vehicles, emissions regulations, promoting public transportation, or taking other actions that would protect the environment.

Understanding reasoning fallacies will make you a more skilled student of argument and a more effective participant in public discussions. If you can identify faulty reasoning, you should also be able to avoid it. Likewise, you can identify and explain reasoning flaws in other speakers’ messages about public issues.