Post Hoc Fallacy Quotes

The cluster illusion, like other post hoc fallacies in probability, is the source of many superstitions: that bad things happen in threes, people are born under a bad sign, or an annus horribilis means the world is falling apart. When a series of plagues is visited upon us, it does not mean there is a God who is punishing us for our sins or testing our faith. It means there is not a God who is spacing them apart.

Together, creeping determinism and sampling bias lead commonsense explanations to suffer from what is called the post-hoc fallacy.

Although the archaeological record is suggestive, it is also frustratingly incomplete; soon after the Spaniards visited, mass graves became more common in the Southeast, but there is yet no solid proof that a single Indian in them died of a pig-transmitted disease. Asserting that De Soto’s visit caused the subsequent collapse of the Caddo and Coosa may be only the old logical fallacy of post hoc ergo propter hoc.

Without awareness of common pitfalls such as confirmation bias, positive-outcome bias, and subjective validation, a person trained in logic and fallacy detection is easily deceived into thinking that he or she has acquired invincible armor against assaults of unreason. Expressions like post hoc ergo propter hoc and false cause, should be informed by knowledge of evolution and how the brain works to jump to conclusions about causal connections.

If we were all equipped with perfectly logical minds, we would see that the number of bad things happening to people who’ve been cursed is the same as the number of bad things happening to everyone else. But that’s not how our minds work. More often, we look for bad things and then work backward. It’s a very old logical fallacy. The Romans called it post hoc, ergo propter hoc, meaning “after this, therefore because of this.” If a piano falls on your head, it’s because you walked under a ladder two weeks ago. Never mind that many people who work in the ladder industry, regularly use ladders, or just happen to walk under them every day manage to avoid falling pianos.

the post hoc, ergo propter hoc fallacy

The result is that we are tempted to infer a cause-and-effect relationship when all we have witnessed is a sequence of events. This is the post-hoc fallacy.