The Most Famous Logical Fallacies Explained

An artistic representation of the human brain.

In psychology, fallacies are errors of thought that somewhat warp our perception of the real world. In this article, we will take a look into some of the most famous logical fallacies and why you should avoid them.

Ad Hominem Fallacy

The ad hominem fallacy happens when there is an attack made against the person rather than the argument being made. For example, if there is a student that’s arguing for a vegetarian diet and another student replies, "You just say that because you're a loser," that would be ad hominem. The strategy here is to try to put down the point by discrediting the person. This fallacy is damaging because it distracts from the actual issues at hand and doesn’t actually help solve problems or realize something during a discussion.

Appeal to Authority

This fallacy occurs when an authoritative figure's opinion is used as evidence, but that opinion is not necessarily supported by any specific expertise related to the subject being examined. For example, whenever anyone says something like, "This diet is healthy, my favorite actor says so," they are making an appeal to authority without considering whether the actor knows enough about nutrition. It's true that expert opinions can be helpful, but they shouldn't provide the basis for an argument in areas where they are not experts themselves.

Confirmation Bias

Probably the most famous on this list, confirmation bias is the tendency to only believe and look for things that confirms existing beliefs and to try to disregard or discredit anything that contradicts them. For instance, in research, it would be like a researcher only selecting data that illustrates his hypothesis and refusing results that do not correspond to his expectations. This can lead to one-sided research and a lack of objectivity, which is important in science.

False Dilemma

Also known as the false dichotomy, this fallacy occurs when someone presents only two options as if they were the only possibilities, whereas in fact, there may be several. A possible example would be a student saying, "You either support this theory or you're against science." This argument ignores the possibility of taking more meet-in-the-middle positions or other kinds of theories. Because of this fallacy, complex questions are reduced to an oversimplified choice.

Straw Man Argument

This is a fallacy where the speaker distorts or exaggerates another's argument just to make it easier to attack or refute. For example, if a person says, "We need to consider reducing sugar intake," and another responds, "So you want to ban all sweets?", that would be creating a straw man. The original argument is distorted so that the counter-argument seems stronger when, in fact, it does not really address the real argument.

Bandwagon Fallacy

The bandwagon fallacy argues that something should be accepted because many people believe it or do it. An example of this would be, "Everyone says that bears are friendly, and therefore, it is right." However, this is a very bad argument: just because it's popular doesn't make it right or valid. The fact that a lot of people believe something doesn’t necessarily make the belief true or appropriate.

Slippery Slope

This fallacy suggests that one event must inevitably follow another without providing any argument on why the chain of events would occur. This would be like someone saying that if we allow students to wear hats in class, they'll soon want to wear whatever they want, leading to chaos. Here, an illogical jump is made from one minor action to an extreme outcome without any evidence.

Appeal to Emotion

Another common fallacy is using emotions to move people instead of arguing with logic. For instance, one might say in a debate on school policies, "Think of how sad the children will be if we change this rule!” In this scenario, emotions serve as a way to go around rational discussion to come to a conclusion. While emotions are important, they should not solely be used as a basis for decisions or arguments.

Post Hoc Ergo Propter Hoc

This Latin phrase translates to "after this, therefore because of this," defining the fallacy whereby a person assumes that because one event follows another, the first must have caused the second. An example of this might be, "Since I started my psych class, I've felt smarter, so the class must be making me smarter." In this case, other variables might also account for this increase in intelligence.

Gambler's Fallacy

The gambler's fallacy is the belief that if something happens more often than is normal during a given period, it will occur less often in the future, and vice versa, even though the odds are the same. For instance, it would be like a person flipping a coin and landing on heads ten times in a row and then assuming that they will land on tails the eleventh time, despite the probability of heads vs. tails still being 50-50. This fallacy affects decision-making not just in gambling but also in different scenarios where certain events are illogically anticipated in order to "balance out the chances."

Sunk Cost Fallacy

The sunk cost fallacy occurs when a person continues a behavior or endeavor as a result of previously invested resources (time, money, effort) that cannot be recovered, even if it’s deemed to be harmful or unnecessary to continue. For example, someone might continue watching a movie they don't enjoy because they've already paid for the ticket, or a company might keep funding a failing project because of the money already spent. This fallacy leads to irrational decisions because they're based on past investments rather than future benefits or rational analysis.

Understanding and Avoiding Fallacies

Understanding such logical fallacies will help people better their critical reasoning abilities. Recognizing that a statement may be fallacious due to these logical errors makes for better debating, clearer thinking, and hence, better research. In everyday life, avoiding these fallacies allows for theories, treatments, and conclusions to come about based on appropriate logical reasoning.

Each of the fallacies described above shows how easily a discussion might be derailed or a person might be misled into believing something based on poor reasoning. These fallacies are quite common, but recognizing them allows for people to not only safely move forward themselves but also help others to do so as well. Avoiding and recognizing these fallacies also allows us to make better decisions regarding choices in life.