Post Hoc Fallacy

Understanding the Post Hoc Fallacy

A post hoc fallacy is like blaming the wrong suspect just because they were at the scene of a crime first. It’s a mistake in logic where someone believes that if one event happens after another one, the first event must have caused the second one. To put it another way, think of it like this: If you water your garden and later it starts to rain, the post hoc fallacy would be thinking your watering caused the rain to fall.

So, another definition could be when we see two events in a row and quickly jump to say that the first one made the second one happen. Like thinking that because you found a dollar on the ground after you put on a green shirt, your green shirt has the power to give you money. But in reality, the two events are not connected—that’s what makes it a post hoc fallacy.

The Logical Mistake of Post Hoc Fallacy

This type of logic goes something like this:

• An event named X takes place.
• Sometime after, another event named Y happens.
• Then, someone makes the error of saying that X is the cause of Y.

It’s a shortcut in thinking that’s easy to take. Yet, when we stop to think more about it, we realize that just because X happened before Y, it doesn’t mean X caused Y to happen. Other factors could be involved, but we’re ignoring them.

Learning from Examples of Post Hoc Fallacy

In Medicine

Let’s look at the old belief about going out into cold night air:

• Someone named Alex stepped outside when it was cold at night and later got sick with malaria.
• Doctors back then thought the cold air at night caused Alex to get sick.

This is a classic post hoc fallacy because those doctors didn’t know about the mosquitoes spreading disease. They saw Alex get sick after being out at night and mistakenly blamed the cold air instead of the real cause. They didn’t realize that the timing was just a coincidence.

In Politics

Imagine a policy discussion going like this:

• Politician A: “Stricter laws on theft will bring down theft rates.”
• Politician B questions how A knows this will work.
• Politician A recalls Senator X getting stricter on theft, and the theft rate dropping soon after.

This is the post hoc fallacy in action because Politician A is oversimplifying things. They ignore other possible factors like increased police patrols or community programs that may have also played a role in reducing theft. They wrongly credit the stricter laws as the sole cause.

In The Media

• Some people notice more kids getting shots and more autism cases.
• They wrongly connect the two, saying the shots cause autism.

However, this poor logic, another post hoc error, overlooks the advances in healthcare. We’ve gotten better at finding autism early, and more kids getting shots just means we’re taking better care of our children’s health. The shots themselves don’t cause autism; they just happen to be part of a time when medical care is improving.

How To Steer Clear of The Post Hoc Fallacy

Avoiding a post hoc fallacy means not jumping to conclusions. It’s about remembering that just because something happens before another thing, it doesn’t automatically mean it’s the cause. To really prove there’s a cause-and-effect relationship, one needs to look at all possibilities and figure out the exact way one event could cause the other. This is why scientists conduct tests and studies to find true connections, rather than just guessing based on the order of events.

Related Topics

Learning about the post hoc fallacy also helps us understand other mistakes in thinking:

• Cum Hoc Fallacy: This happens when we mistakenly believe that if two things occur at the same time, one must be the cause of the other. It’s like saying because kids play more video games now, and there’s more sugar in food, one must be causing the other, which isn’t necessarily the case.
• Gambler’s Fallacy: This is when someone thinks that if something happens often now, it won’t happen as much later, or the opposite. It’s like flipping a coin and getting heads five times, then thinking tails must be next, even though each flip has an equal chance.
• Confirmation Bias: Confirmation bias is when people like information that supports what they already think, even when the facts are weak or the connection isn’t real. It’s like only listening to news that agrees with your opinions and ignoring anything different.

Exploring these topics can sharpen our thinking skills and help us recognize and avoid jumping to false conclusions.

Summarizing the Post Hoc Fallacy

In short, the post hoc fallacy is a faulty shortcut in thinking. When you think that because one event follows another, the first must be the reason for the second, you’re probably making this error. It’s a common mistake, like believing a rooster’s crow causes the sunrise, a lucky charm leads to good luck, or a vaccine creates a health condition. Real-life causes are often more complex and need more careful exploration.

By being aware of this fallacy, we can escape the trap of incorrect cause-and-effect thinking, whether looking at events in history, current political decisions, or the medicine we use. The way to smarter conclusions is asking questions, testing ideas, and looking for true evidence of a link, instead of assuming one is there right away.