Post-Hoc Argument

Post-Hoc Fallacy Argument

Post-hoc arguments often wrongly identify the cause of something when there is not enough information to properly understand what happened. Multiple events can happen closely together and appear like one caused the other. This faulty attribution of cause is called the post hoc ergo propter hoc fallacy.

Fallacies of causation come from misinterpreting the ways in which causes and effects are related.

Common Problems in Causal Reasoning

Faulty post-hoc arguments are often the result of related problems in causal reasoning. In other words, errors occur when causal relationships are not understood.

Correlation is not causation

Since the causal chain is the most common type of causal reasoning, people often mistake common-cause, common-effect, and systemic relationships as causal chains. But factors can work together to produce a shared effect, as in the relationship between poverty and crime. This process is called correlation.

Fig. 2 - A virtual reality gamer. The relationship between aggressive behaviors and playing violent video games continues to generate controversy.

The popularity of violent video games has sown much concern among parents and teachers who debate whether children's exposure to violent media explains the origin of aggressive behaviors. Following much exhaustive research since the 1990s, the American Psychological Association has repeatedly confirmed that no sufficient link has been established between exposure to violent video games and the onset of aggressive behaviors.¹

The line of reasoning connecting the two often neglects the ways in which playing video games and aggressive behaviors are correlated, meaning how they appear together in a larger web of factors. Violent thoughts and feelings often appear in people who lack stable and caring social networks, and the lack of healthy social relations is often associated with increased solitary activities, including media consumption. Therefore, aggressive behaviors and unhealthy media consumption are correlated in a larger social context. To claim that one causes the other is to commit a fallacy of causal reasoning.

Non Causa Pro Causa

Non causa pro causa (often shortened to simply non causa) is often called in English questionable cause.

There is much overlap between the post hoc fallacy, the confusion of correlation and causation, and the non causa fallacy. The non causa fallacy, however, generally mistakes the direction in which the cause and effect are related. In the previous example, claiming that health insurance causes people to visit the hospital is a non causa fallacy because it mistakes the direction of the cause/effect relationship. Instead of causing people to be sick, health insurance allows people to seek medical care when they need it. People with health insurance can go to the hospital when they are sick, while people without health insurance will avoid hospital bills even when they need hospitalization.

Fig. 3 - A cause may be misunderstood.

Post-Hoc Argument Examples

Here's an example of a post-hoc argument.

It's important to be able to analyze such an argument.

Analysis

To properly analyze the man's claim, one must consider what is known.

• It is known that the man had a cough.
• It is known that the reasons for the cough were not the man's health.
• It is known that his cough suddenly stopped, and it stopped after he changed the side of the bed he slept on.

Next, one must identify what is unknown.

• The man's family medical history is unknown.
• The air quality of the man's bedroom is unknown.
• The original cause of the man's cough remains unknown.
• How changing the side of the bed would stop a cough remains unknown.

Then, one must identify what is possible.

• It is possible that changing the side of the bed cured his cough.
• It is possible that another factor, like the air quality of his room, may have affected his cough.

Finally, one must identify whether any of the possibilities can be supported by evidence.

• The man could then sleep on the original side of the bed and see if his cough returns.
• The man could also have the building materials of his house and the air quality of his bedroom tested.

To properly analyze the situation, one must take into account the situation's knowns, unknowns, possibilities, and evidence. To claim that changing the side of the bed cured the man's cough is a post hoc ergo propter hoc fallacy because there is no evidence to support it as the cause of the cough's disappearance.

Identifying and Avoiding a Post-Hoc Fallacy

English language courses and tests require students to read and evaluate texts, many of which are argumentative and may contain faulty reasoning. If you come across an argument that focuses on causal relationships, ask yourself what types of causal relationships could exist between each of the factors.

When writing your own essays and arguments, it is important to avoid committing these same fallacies. Pay close attention to the words you use to describe the relationships between things.

If you cannot identify a cause that is supported by evidence at hand, then use hedging terms that suggest some doubt: "potential," "possible," or "likely." Support your claims with evidence and consider the possible disagreements your reader might have with your ideas. Being able to think one step ahead of your reader is the key to successful argumentation.

¹ "APA Reaffirms Position on Violent Video Games and Violent Behavior." American Psychological Association. 2020.

² Justin Peters. “When Ice Cream Sales Rise, So Do Homicides. Coincidence, or Will Your Next Cone Murder You?” Slate. 2013.

³ Henry K. Beecher. "The Powerful Placebo." Journal of the American Medical Association, vol. 159, no. 17, pp. 1602-1606. 1955.