3.5 Logical Fallacies

Using ethos, pathos, and logos in an argument does not mean that the argument made is necessarily a good one. In academia, especially, we care a lot about making our arguments logically sound; we care about logos. We seek to create work that is rooted in rational discourse. We seek to produce our own rational discourse. We value carefully researched, methodically crafted work. Thus, to be a strong academic writer, you should seek to avoid logical fallacies, which are flaws in reasoning.

Fallacy means false. Think of the concept of a logical fallacy as something that makes an argument problematic, open to attack, or weak. In academic discourse, logical fallacies are seen as failures—as things you will want to avoid.

Thinking about fallacies can be confusing because you see them all the time: in advertising, in conversation, in political discourse. Fallacies are everywhere. But as students of rhetoric, part of your job is to spend time identifying these fallacies in both your own writing and in others’ as a way to avoid them.

Logical Fallacies: A Short List

Generalization—A conclusion or judgment made from insufficient evidence. When one piece of evidence or information is used to make a broad conclusion or statement.

Cherry Picking—Picking and choosing only some of the available evidence in order to present only points most favorable to your point of view. If someone knowingly chooses certain (favorable) pieces of information and conveniently ignores less favorable information, then the argument is not supported by all of the available research.

Straw Man—An oversimplification of an opposing perspective so that it becomes easy to attack. This is unfair and illogical because when one oversimplifies or inaccurately represents an argument and refutes that oversimplified version, one is not actually addressing the argument.

Red Herring—Changing topics to avoid the point being discussed. This is an argument tactic in which one attempts to change the conversation, often by bringing up information that is not relevant to the claim or point being debated, in order to try to control the conversation. This can be a way to avoid having to address or answer the question at hand, and it harms the quality of an argument.

Ad Hominem—It is a personal attack rather than a way of engaging with someone’s ideas. For example, “You are an idiot! That’s why you’re wrong!” This type of logical fallacy occurs when an arguer attacks or insults the person making opposing arguments instead of attacking the ideas, the logic, or the evidence within the opposing argument itself. It is a personal attack rather than a way of engaging with someone’s ideas.

Ad Populum—A misused reference to popularly accepted values. For instance, “This is about freedom and righteousness, and if you believe in those things, then you should believe my argument.” This is an example of misused ethos—when the author is referencing the values that the audience cares about so that they think only about the values and not about the content of the argument (or, likely, the fact that there is little intellectual substance in what is being said).

Either/Or—This is an argument that attempts to create a situation of absolutes with no options in between. For example, “Either we intervene, or we are basically no better than the Nazis.” This thinking is fallacious because it assumes that there are only two options, with nothing in between.

Slippery Slope—This is a fallacy that assumes that one thing is going to have a series of consequences or effects—often leading to a worst-case scenario. For example, “If we let this happen, then that will happen and then the worst possible thing will happen.” It is false reasoning because 1) it’s impossible to predict the future, 2) it is illogical to suggest that one action will always necessarily lead to the worst possible outcome, and 3) it assumes a very specific chain of future events. This “if we let this happen there will be some horrible end” is a misuse of cause/effect reasoning, often with some pathos (fear) sprinkled in.

When you are reading others’ arguments, see if any of their reasoning is actually one of these fallacies of logic.

You may also find a longer list of logical fallacies here.

As you draft ideas for your own arguments, test each of your reasons against these definitions: have you used any of these fallacies to build your reasoning? If so, keep revising your line of reasoning!