A Complete Guide to Logical Fallacies
What are Logical Fallacies?
If it looks like a duck, walks like a duck and quacks like a duck then it must be a duck, right? Not necessarily. A wild wood duck is also known as a maned goose, while an Egyptian Goose is actually a duck!
In debates, occasionally you will stumble upon arguments that sound like convincing logical arguments, but they are actually members of the “logical fallacies” family. Logical fallacies are common flaws in the reasoning and logic of arguments – mistakes that are made so commonly that over time they have come to earn their own names. In fact, many logical fallacies were identified and categorized way back in Ancient Greece – but we’re still making them two and a half thousand years later, both in political debate and also schools debate - so don't feel too bad about falling prey to the same traps!
How to deal with logical fallacies
One thing that’s important to note before we begin is that if you hear your opponent commit a logical fallacy in a debate, you shouldn’t simply say, “Judge, my opponent committed a logical fallacy!” No. It’s your responsibility to explain exactly where your opponents are wrong, and how their use of these formal fallacies affects the debate, just like how you should do for any other rebuttal point. You can use the classic four-step rebuttal framework to discredit their flawed reasoning:
- “They said...” – briefly summarize in a sentence or two what your opponents said.
- “This is a logical fallacy because...” – then say which logical fallacy they are guilty of and why.
- “We say...” – explain your side of this argument.
- “Therefore...” – explain the effect on the debate, for example, “their point doesn't stand while our impact stands true.”
Now, the first logical fallacy we’re going to look at is called the “slippery slope.” This is an argument with a broad and flimsy structure that leads to many, often extreme or even impossible, consequences. It’s also common when speakers claim an exaggerated impact, without adding the logical links to show that it is realistic. For example: “Banning homework will make children happy, which in turn will make their parents happy. Happier parents will spend more money on charitable causes, and therefore banning homework will solve poverty.”
If you hear your opponent make a grand and sweeping result as their impact, you can challenge the strength of their logical links. You should explain that there is a huge gap between their different parts of their reasoning, and between the reasoning and impact so that their impact unrealistic. What does this look like in practice? Let’s see.
My opponent claimed banning homework will solve poverty. However, their logic is deeply flawed because they have no links that explain or prove how happy parents are going to be. They also don’t show that the parents’ happiness will translate to charitable donations, which makes this point a slippery slope. We say that there are many other factors that make parents donate to charity, such as budget considerations, personal interests, and trust. This means that just because their child is a bit happier, it doesn’t mean that parents will donate, and definitely not to the extent that it will solve poverty. Therefore, the other team has presented an unrealistic impact they never reach, so it shouldn't be credited.
The second fallacy is known as “appeal to authority.” This happens when a debater uses a quotation or piece of evidence from an authority figure, such as an expert or a politician, to prove that something is true. To be clear, in some forms of debating, it is not only useful but required to provide evidence! But whether or not something is true doesn’t depend on the testimony of one person, however learned and clever they are.
For example, using a quotation from an eminent scientist to prove that manmade climate change is real may be persuasive as supporting evidence in some formats of debate (for example, Public Forum), but not in BP or WSDC debate:
Our opponents tried to downplay the importance of fighting climate change, by giving some reasons why reducing carbon emissions is supposedly not as important a priority as dealing with poverty or homelessness. But according to eminent scientific writer Stephen Jay Gould, “manmade climate change is the most pressing problem that we face as a civilization”, so we can see that this Opposition argument falls.
This would be a great hook or introduction to an argument, but as a piece of logic it is lacking! If we know that climate change is a real and pressing problem, it’s because a huge preponderance of scientific evidence points in that direction – not because a popular science author says so. Providing evidence makes sense to support your claim - but not to prove it.
So far, we’ve covered two common logical fallacies. Let’s have a look at three more.
A third common logical fallacy in debate is hasty generalization, also known as the “general rule” fallacy. This is an argument that makes a generalized claim based on a specific case or example. The problem with this is that even if something has been true in one case, some cases, or even most cases, that doesn't mean it will always be true in all circumstances. This logical fallacy usually happens when an opponent argues using personal examples or anecdotal stories as their only evidence for general claims. For example:
Homework is necessary for students to remember and practice the knowledge they learn in school. When I don’t do my homework, I can’t remember what we learned in class, and then I perform poorly on exams. But every time I do my homework, I do much better in exams. If you remove homework, it will make learning in school inefficient and pointless.
If you hear your opponent present one or even a couple of examples, from which they conclude a general statement or impact, and then claim that it applies to every situation, they are committing this fallacy. You should explain in your rebuttal that one or some examples can’t guarantee their general claim or impact applies in all situations. You should also give one or two counter examples of your own, to disprove their logic. How do you do this? Let’s see.
Our opponents have stated that without homework students will forget everything that they learned and perform poorly in exams. However, this argument is false because it’s based on just one personal example and assumes that all students need homework to remember class material and do well in exams. We say that there are many students who don’t do homework and still remember enough to perform well, including myself and my teammate. Therefore, this argument isn’t a valid reason to keep homework for all students, just because our opponents say they can’t remember material without it.
Now, if you look carefully at the argument we just rebutted, you might notice that even though it sounds reasonable, there are actually two more logical fallacies hidden there! Boy did this opponent mess up their point...
One of them is called the “excluded middle” fallacy. This is when you present a situation as if there are only two, often extreme or opposite, options available while ignoring a reasonable and often more persuasive middle ground. This is also referred to as the false dichotomy fallacy. A dichotomy is when there is realistically two opposite choices or outcomes in a given situation. A false dichotomy is thus when there are other realistic possibilities or outcomes. The previous example was claiming we either have homework, or we perform poorly on exams. To answer this fallacy, you could say:
My opponent claims that either students are assigned homework, or they will perform poorly on exams. However, this is a false dichotomy. They are presenting the situation as if there are only two options – assigning homework or failing exams, when in reality there are more options. We say that there are many methods to study for exams and improve your grades that don’t require regular homework, such as designated study groups. Therefore, there are more and even better options then our opponent is presenting and there is not inherent need for homework.
This is an example of how to rebut the false dilemma fallacy that can be adapted to many situations, as well as helping you to strengthen your own arguments!
The other logical fallacy in the original example is confusing correlation and causation. Causation means that one thing causes another thing to exist. For example, homework can help students feel more confident before exams. The feeling of confidence has been caused by the homework. A correlation is when two things exist at the same time, but neither is the cause of the other. For example, if a student did homework, and was hungry at the same time, that doesn’t mean the student is hungry because of the homework. There could be many reasons why the student is hungry.
In our example, who says that our opponent didn’t do well on exams because they didn't do homework? Maybe they didn’t do so well because the exam was extra hard? Or because they were hungry or didn’t get a good night’s sleep before the exam? The fact that they didn’t do homework and didn’t do well on the exam at the same time, doesn’t mean that one has caused the other. Your opponent is confusing correlation and causation. Which is exactly what you should say in your rebuttal!
By now you’re probably looking back on previous speeches you delivered or heard, and realizing that they had at least a couple of logical fallacies, right? Well, after this lesson, you’ll know what to do any time a duck-looking goose – sorry, a logical fallacy – pops up.
The last common fallacy we’ll look at is the “straw man” fallacy. This is when a speaker creates, and then attacks, either an extreme or a weak version of their opponent's argument and misrepresents its actual intention. This is a bad strategy because it means that your rebuttal isn’t addressing the actual argument you’re trying to rebut.
For example, let’s say you argued that homework is stressful and takes a lot of time. Your opponents reply: “The other team stated that homework makes students so stressed and depressed that they basically can’t function and their whole lives are ruined. But in reality, we see most students are dealing with homework quite fine.”
What you should do next is to clarify that your opponents are misrepresenting your point, explain what you were really claiming, and highlight to the judge that your opponent didn't actually answer your argument but instead put up a straw man argument.
What does this look like in practice?
Our opponents claim that our point was that no students can ever function when homework exists. However, that is a mischaracterization of our point. What we said was that because of homework, students are stressed and miss out on opportunities to play with friend or do more enjoyable things. Therefore, they have attacked a strawman and didn’t provide an answer to our actual argument, which therefore still stands strong in the debate.
How to avoid logical fallacies
At this point you must be thinking, “With so many logical fallacies out there, how can I successfully avoid making any?” Here we can give you three take-away tips:
- Firstly, make sure you explain every step of your reasoning, and that each step is logically connected to the previous step and to the following one.
- Secondly, don’t rely on extreme examplesthat only show the very best or very worst of something, and don’t rush to generalizations. Ask yourself what seems most probable in real life.
- Thirdly, listen attentively to your opponentsand take clear notes on what they are actually saying.
Congratulations! You now know how to identify, rebut and avoid six of the most common logical fallacies in public speaking and debate. There are other logical fallacies out there, so we encourage you to go and research them, and use all this information to your advantage in future competitions.
To conclude, even though wild wood ducks sound like ducks, look like ducks and behave like ducks, they’re actually geese, and knowing the difference between the two can save your life. Good luck! (Quack quack!)