4 – Persuasion

Avoiding Logical Fallacies

David McMurrey; Anonymous; Matt McKinney; and Nicole Hagstrom-Schmidt

In addition to considering the most effective tools and strategies for persuading their audiences, communicators must be mindful about avoiding logical fallacies. The term logical fallacy refers to a structural flaw in an argument that inherently weakens it. A logical fallacy therefore occurs not necessarily when information itself is false or wrong, but when a communicator puts material together in a way that makes their conclusions invalid.

Logical fallacies do not always reflect the integrity of a position. It is very possible to make a bad argument for a good cause. For example, a nutritionist can make a very reasonable case for becoming a vegan by drawing from scientific research on the health benefits of a plant-based diet, the social and environmental impacts of factory farming, and their experiences as a professional. However, if the nutritionist were to argue, “Going vegan is the right thing to do because Benjamin Franklin would have wanted it,” or “Anyone who eats meat is a sociopath,” then they would undermine their position by the faultiness of their reasoning.

To audiences, the presence of logical fallacies in a speaker’s or writer’s argument can be indicative of a lack of thorough thinking or even arguing in bad faith. Thus, being aware of the different types of logical fallacies and testing your argument against them is essential to effective persuasion. Table 4.1 below lists common logical fallacies, their definitions, and examples of how they might be used in a speech or written document.

Table 4.1. Logical fallacies.

Logical Fallacy Definition Example
Red Herring Distracting attention from the main issue, particularly by relating the issue to a common fear. It’s not just about the death penalty; it’s about the victims and their rights. You wouldn’t want to be a victim, but if you were, you’d want justice.
Straw Man Setting up a weak argument to be easily refuted, thus distracting attention from stronger arguments. What if we released criminals who commit murder after just a few years of rehabilitation? Think of how unsafe our streets would be then!
Begging the Question Claiming the truth of the very matter in question, as if it were already an obvious conclusion. We know that they will be released and unleashed on society to repeat their crimes again and again.
Circular Argument Using the proposition to prove itself. Assumes the very thing it aims to prove. Related to begging the question. Once a killer, always a killer.
Ad Populum “Appeal to the people.” Appealing to a common belief of some people, often prejudicial, and stating that everyone holds this belief. Also called the Bandwagon Fallacy, as people “jump on the bandwagon” of a perceived popular view. Most people would prefer to get rid of a few “bad apples” and keep our streets safe.
Ad Hominem “Argument against the man” instead of against the person’s message. Stating that someone’s argument is wrong solely because of something about the person rather than about the argument itself. Our representative is a drunk and philanderer. How can we trust him on the issues of safety and family?
Non Sequitur “It does not follow.” Offering a conclusion that does not follow from the premises. They are not related. Since the liberal anti-war demonstrations of the 1960s, we’ve seen an increase in convicts who got let off death row.
Post Hoc Ergo Propter Hoc “After this, therefore because of this.” Arguing that one event caused another simply because it came first. Also called a coincidental correlation or false causality. Hurricanes have become more frequent and severe since we got rid of prayer in schools.
Hasty Generalization Drawing a conclusion based on too little evidence. A lot of people wear burnt orange in Austin, so most Texans must be Longhorn fans.
Either-Or/False Dichotomy Either-Or/False Dichotomy Reducing the number of available choices to two: one you favor and one that is completely unreasonable. Either we drill for oil in national parks or our way of life collapses entirely.
False Analogies Basing an entire persuasive effort on an analogy. This is flawed because all analogies break down at some point, and some are just wrong to begin with. Earth must be flat because when I pour water on an orange it runs off; it doesn’t sit there and collect like the oceans do.
Loaded Language Using words that have a secondary evaluative meaning (usually negative) through their connotations, rather than neutral and descriptive terms. Looters roamed the streets, carrying goods in the wake of the storm.

vs.

Hurricane survivors traversed the wreckage carrying their possessions.

Whataboutism or

Tu Quoque (“You Also”)

Changing the subject in order to deflect criticism and avoid responding to the original argument. Often rooted in a false moral equivalence. Face masks should not be mandated for public health. What about junk food and cigarettes? We’re not banning those.

This text was derived from

McMurrey, David. Online Technical Writing. n.d. https://www.prismnet.com/~hcexres/textbook/. Licensed under a Creative Commons Attribution 4.0 International License.

University of Minnesota. Business Communication for Success. Minneapolis: University of Minnesota Libraries Publishing, 2015. https://open.lib.umn.edu/businesscommunication/. Licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.

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Howdy or Hello? Technical and Professional Communication by David McMurrey; Anonymous; Matt McKinney; and Nicole Hagstrom-Schmidt is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License, except where otherwise noted.

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