A logical fallacy is a pattern of reasoning that contains a flaw, either in its logical structure or in its underlying premises.

An example of a logical fallacy is the false dilemma, which is a logical fallacy that occurs when a limited number of options are incorrectly presented as being mutually exclusive to one another or as being the only options that exist, in a situation where that isn’t the case. For instance, a false dilemma occurs in a situation where someone says that we must choose between options A or B, without mentioning that option C also exists.

Fallacies, in their various forms, play a significant role in how people think and in how they communicate with each other, so it’s important to understand them. As such, the following article serves as an introductory guide to logical fallacies, which will help you understand what logical fallacies are, what types of them exist, and what you can do in order to counter them successfully.

Examples of logical fallacies

One example of a logical fallacy is the ad hominem fallacy, which is a fallacy that occurs when someone attacks the source of an argument directly, without addressing the argument itself. For instance, if a person brings up a valid criticism of the company that they work in, someone using the ad hominem fallacy might reply by simply telling them that if they don’t like the way things are done, then that’s their problem and they should leave.

Another example of a logical fallacy is the loaded question fallacy, which occurs when someone asks a question in a way that presupposes an unverified assumption that the person being questioned is likely to disagree with. An example of a loaded question is the following:

“Can you get this task done for me, or are you too busy slacking off?”

This question is fallacious, because it has a flawed premise, and specifically because it suggests that if the person being questioned says that they can’t get the task done, then that must be because they’re too busy slacking off.

Finally, another example of a logical fallacy is the argument from incredulity, which occurs when someone concludes that since they can’t believe that a certain concept is true, then it must be false, and vice versa. For instance, this fallacy is demonstrated in the following saying:

“I just can’t believe that these statistics are true, so that means they must be false.”

In this case, the speaker’s reasoning is fallacious, because their premises are flawed, and specifically their assumption that if they can’t believe the statistics that they’re shown are true, then that must mean that the statistics are false.

Formal and informal logical fallacies

There are two main types of logical fallacies:

Formal fallacies. A formal logical fallacy occurs when there is a flaw in the logical structure of an argument, which renders the argument invalid. For example, a formal fallacy can occur because the conclusion of the argument isn’t based on its premises.

A formal logical fallacy occurs when there is a flaw in the logical structure of an argument, which renders the argument invalid. For example, a formal fallacy can occur because the conclusion of the argument isn’t based on its premises. Informal fallacies. An informal logical fallacy occurs when there is a flaw in the premises of an argument, which renders the argument unsound. For example, an informal fallacy can occur because the premises of an argument are false, or because they’re unrelated to the discussion at hand.

Therefore, there are two main differences between formal and informal logical fallacies. First, formal fallacies contain a flaw in their logical structure, while informal fallacies contain a flaw in their premises. Second, formal fallacies are considered to be invalid patterns of reasoning, while informal fallacies are considered to be unsound patterns of reasoning, despite the fact that they can still be valid.

For instance, the following is an example of a formal fallacy:

Premise 1: If it’s raining, then the sky will be cloudy. Premise 2: The sky is cloudy. Conclusion: It’s raining.

Though both the premises in this example are true, the argument is considered to be invalid, since there is a flaw in its logical structure.

Specifically, premise 1 tells us that if it’s raining, then the sky will be cloudy, but that doesn’t mean that if the sky is cloudy (which we know it is, based on premise 2), then it’s necessarily raining. That is, it’s possible for the sky to be cloudy, without it raining, which is why we can’t reach the conclusion that is specified in the argument, and which is why this argument is invalid, despite the fact that its premises are true.

On the other hand, the following is an example of an informal fallacy:

Premise 1: The weatherman said that it’s going to rain next week. Premise 2: The weatherman is always right. Conclusion: It’s going to rain next week.

Here, the logical structure of the argument is valid. Specifically, since premise 1 tells us that the weatherman said that it’s going to rain next week, and premise 2 tells us that the weatherman is always right, then based on what we know (i.e. on these premises), we can logically conclude that it’s going to rain next week.

However, there is a problem with this line of reasoning, since our assumption that the weatherman is always right (premise 2) is false. As such, even though the logical structure of the argument is valid, the use of a flawed premise means that the overall argument is considered to be unsound.

Overall, a sound argument is one that has a valid logical structure and true premises. A formal logical fallacy means that the argument is invalid, due to a flaw in its logical structure, which also means that it’s unsound. An informal logical fallacy means that the argument is unsound, due to a flaw in its premises, even though it has a valid logical structure.

Example of a formal logical fallacy

As we saw above, a formal fallacy occurs when there is an issue with the logical structure of an argument, which renders the argument invalid.

An example of a formal logical fallacy is the masked-man fallacy, which is committed when someone assumes that if two or more names or descriptions refer to the same thing, then they can be freely substituted with one another, in a situation where that’s not the case. For example:

Premise 1: The citizens of Metropolis know that Superman saved their city. Premise 2: Clark Kent is Superman. Conclusion: The citizens of Metropolis know that Clark Kent saved their city.

This argument is invalid, because even though Superman is in fact Clark Kent, the citizens of Metropolis don’t necessarily know Superman’s true identity, and therefore don’t necessarily know that Clark Kent saved their city. As such, even though both the premises of the argument are true, there is a flaw in the argument’s logical structure, which renders it invalid.

Example of an informal logical fallacy

As we saw above, an informal fallacy occurs when there is a flaw in the premises of an argument, which renders the argument unsound.

An example of an informal logical fallacy is the strawman fallacy, which occurs when a person distorts their opponent’s argument, in order to make it easier to attack. For example:

Alex: I think we should increase the education budget. Bob: I disagree, because if we spend the entire budget on education, there won’t be any money left for other essential things.

Here, Bob’s argument is valid from a formal, logical perspective: if we spend the entire budget on education, there won’t be anything left to spend on other things.

However, Bob’s reasoning is nevertheless fallacious, because his argument contains a false, implicit premise, and namely the assumption that when Alex suggests that we should increase the education budget, he means that the entire budget should be allocated to education. As such, Bob’s argument is unsound, because it relies on flawed premises, and counters an irrelevant point that his opponent wasn’t trying to make.

Fallacious techniques that aren’t logical fallacies

The term ‘fallacious’ has two primary meanings:

Containing a logical fallacy.

Tending to deceive or mislead.

Accordingly, some misleading rhetorical techniques and patterns of reasoning can be described as “fallacious”, even if they don’t contain a logical fallacy.

For example, the Gish gallop is a fallacious debate technique, which involves attempting to overwhelm your opponent by bringing up as many arguments as possible, with no regard for the relevance, validity, or accuracy of those arguments. Though a Gish gallop may have some arguments that contain logical fallacies, it isn’t a single argument by itself, and therefore isn’t considered a logical fallacy. However, because its overall argumentation pattern revolves around the intent to deceive, this technique is said to be fallacious.

In this regard, note that logical fallacies, in general, tend to include a form of reasoning that is not only logically invalid or unsound in some way, but that is also misleading.

However, it’s important to keep in mind that fallacies and other fallacious techniques aren’t always used with the intention of misleading others. Rather, people often use fallacious arguments unintentionally, both when they’re talking to other people, as well as when they conduct their own internal reasoning process, because the fact that such arguments are misleading can lead those who use them to not notice that they’re flawed in the first place.

Logical fallacies aren’t simply factual errors

It’s important to note that logical fallacies are errors in reasoning, rather than simple factual errors.

For example, though the statement “humans are birds” is flawed, that’s because it contains a simple factual error, rather than a logical fallacy. Conversely, the argument “humans have eyes, and birds also have eyes, therefore humans are birds” contains a logical fallacy, since there is a flaw in its logical structure, which renders it invalid.

How to counter logical fallacies

To counter the use of a logical fallacy, you should first identify the flaw in reasoning that it contains, and then point it out and explain why it’s a problem, or provide a strong opposing argument that counters it implicitly.

For example, consider a situation where someone uses the appeal to nature, which is an informal logical fallacy that involving claiming that something is either good because it’s considered ‘natural’, or bad because it’s considered ‘unnatural’.

Once you’ve identified the use of the fallacy, you can counter it by explaining why its premises are flawed. To achieve this, you can provide examples that demonstrate that things that are “natural” can be bad and that things that are “unnatural” can be good, or you can provide examples that demonstrate the issues with trying to define what “natural” and “unnatural” mean in the first place.

The steps in this approach, where you first identify the use of the fallacy and then either explain why it’s a problem or provide strong counterarguments, are generally the main ones to follow regardless of which fallacy is being used. However, there is some variability in terms of how you implement these steps when it comes to different fallacies and different circumstances, and an approach that will work well in one situation may fail in another.

For example, while a certain approach might work well when it comes to resolving a formal fallacy that you’ve used unintentionally in your own reasoning process, the same approach might be ineffective when it comes to countering an informal fallacy that was used intentionally by someone else for rhetorical purposes.

Finally, it’s also important to keep in mind that sometimes, when responding to the use of fallacious reasoning, dismantling the logic behind your opponent’s reasoning and highlighting its flaws might not work. This is because, in practice, human interactions and debates are highly complex, and involve more than just exchanging logically sound arguments with one another.

Accordingly, you should accept the fact that in some cases, the best way to respond to a logical fallacy in practice isn’t necessarily to properly address it from a logical perspective. For example, your best option might be to modify your original argument in order to counter the fallacious reasoning without explicitly addressing the fact that it’s fallacious, or your best option might be to refuse to engage with the fallacious argument entirely.

Account for unintentional use of fallacies

When you counter fallacies that other people use, it’s important to remember that not every use of a logical fallacy is intentional, and to act accordingly, since accounting for this fact can help you formulate a more effective response.

A useful concept to keep in mind in this regard is Hanlon’s razor, which is a philosophical principle that suggests that when someone does something that leads to a negative outcome, you should avoid assuming that they acted out of an intentional desire to cause harm, as long as there is a different plausible explanation for their behavior. In this context, Hanlon’s razor means that, if you notice that someone is using a logical fallacy, you should avoid assuming that they’re doing so intentionally, as long as it’s reasonable to do so.

In addition, it’s important to remember that you too might be using logical fallacies unintentionally in your thinking and in your communication with others. To identify cases where you are doing this, try to examine your reasoning, and see if you can identify any flaws, either in the way that your arguments are structured, or in the premises that you rely on in order to make those arguments. Then, adjust your reasoning accordingly, in order to fix these flaws.

Make sure that an argument is fallacious before countering it

Before you counter an argument that you think is fallacious, you should make sure that it is indeed fallacious, to the best of your ability.

There are various ways to do this, including slowing down your own reasoning process so you can properly think through the argument, or asking the person who proposed the argument to clarify their position.

The approach of asking the other person to clarify their position is highly beneficial in general, because it helps demonstrate that you’re truly interested in what the other person has to say. Furthermore, in cases where the argument in question does turn out to be fallacious, this approach can often help expose the issues with it, and can also help the other person internalize these issues, in a way that you won’t always be able to achieve by pointing them out yourself.

Finally, note that a useful tool to remember in this regard is the principle of charity, which is a philosophical principle that denotes that, when interpreting someone’s statement, you should assume that the best possible interpretation of that statement is the one that the speaker meant to convey. In this context, the principle of charity means that you should not attribute falsehoods, logical fallacies, or irrationality to people’s argument, when there is a plausible, rational alternative available.

Remember that just because an argument is fallacious, that doesn’t mean that its conclusion is false

It’s important to keep in mind that even if an argument is fallacious, it can still have a true conclusion. Assuming that just because an argument is fallacious then its conclusion must necessarily be false is a logical fallacy in itself, which is known as the fallacy fallacy.

For instance, consider the following example of a formal logical fallacy (which we saw earlier, and which is known as affirming the consequent):

Premise 1: If it’s raining, then the sky will be cloudy. Premise 2: The sky is cloudy. Conclusion: It’s raining.

This argument is logically invalid, since we can’t be sure that its conclusion is true based on the premises that we have (because it’s possible that the sky is cloudy but that it’s not raining at the same time). However, even though the argument itself is flawed, that doesn’t mean that its conclusion is necessarily false. Rather, it’s possible that the conclusion is true and that it is currently raining; we just can’t conclude this based on the premises

The same holds for informal fallacies. For example, consider the following argument:

Alex: It’s amazing how accurate this personality test I took is. Bob: No it isn’t, it’s pure nonsense.

Here, Bob is using an appeal to the stone, which is a logical fallacy that occurs when a person dismisses their opponent’s argument as absurd, without actually addressing it, or without providing sufficient evidence in order to prove its absurdity. However, even though Bob’s argument is fallacious, that doesn’t mean that its conclusion is wrong; it’s possible that the personality test in question is indeed nonsense, we just can’t tell whether that’s the case based on this argument alone.

Overall, the important thing to understand is that an argument can be fallacious and still have a conclusion that is factually correct. To assume otherwise is fallacious, which is why you shouldn’t discount people’s conclusions simply because the argument that they used to reach those conclusions contains a logical fallacy.

The difference between logical fallacies and cognitive biases

While logical fallacies and cognitive biases appear to be similar to each other, they are two different phenomena. Specifically, while logical fallacies are flawed patterns of argumentation, and are therefore a philosophical concept, cognitive biases are systematic errors in cognition, and are therefore a psychological concept.

Cognitive biases often occur at a more basic level of thinking, particularly when they’re rooted in people’s intuition, and they can lead to the use of various logical fallacies.

For example, the appeal to novelty is a logical fallacy that occurs when something is assumed to be either good or better than something else, simply because it’s perceived as being new and novel.

In some cases, people might use this fallacy due to a cognitive bias that causes them to instinctively prefer things that they perceive as newer. However, people can experience this instinctive preference for newer things without it leading to the use of the appeal to novelty, in cases where they recognize this preference and account for it properly. Furthermore, people can use arguments that rely on the appeal to novelty even if they don’t experience this instinctive preference, and even if they don’t truly believe in what they’re saying.

Overall, the main difference between logical fallacies and cognitive biases is that logical fallacies are a philosophical concept, that has to do with argumentation, while cognitive biases are a psychological concept, that has to do with cognition. In some cases, there is an association between cognitive biases and certain logical fallacies, but there are many situations where one appears entirely without the other.

Summary and conclusions