The Post Hoc Ergo Propter Hoc Fallacy
Assumes that because one event follows another, the first caused the second.
- •Definition: Assumes that because one event follows another, the first caused the second.
- •Impact: Post Hoc Ergo Propter Hoc distorts reasoning by Sequence is not sufficient to establish causality. Without controls or evidence, the conclusion is speculative.
- •Identify: Look for patterns like Observe that Event A happened before Event B.
What is the Post Hoc Ergo Propter Hoc fallacy?
Temporal order alone does not prove causation. Post hoc reasoning overlooks alternative causes, coincidence, and underlying variables.
People lean on this pattern because Temporal proximity is salient; humans seek patterns and causes, sometimes too eagerly.
- 1Observe that Event A happened before Event B.
- 2Conclude A caused B because of the sequence.
- 3Ignore other causal explanations or evidence.
Why the Post Hoc Ergo Propter Hoc fallacy matters
This fallacy distorts reasoning by Sequence is not sufficient to establish causality. Without controls or evidence, the conclusion is speculative.. It often shows up in contexts like Policy evaluation, Personal beliefs, Marketing claims, where quick takes and ambiguity can hide weak arguments.
Examples of Post Hoc Ergo Propter Hoc in Everyday Life
A policy is declared effective because a metric improved afterward, without controlling for other factors or trends.
Why it is fallacious
Sequence is not sufficient to establish causality. Without controls or evidence, the conclusion is speculative.
Why people use it
Temporal proximity is salient; humans seek patterns and causes, sometimes too eagerly.
Recognition
- Causal claim rests mainly on chronology.
- No control for confounders or alternative explanations.
- Assumes inevitability without tests or comparisons.
Response
- Ask for controlled comparisons or additional evidence.
- Identify other variables that could explain the outcome.
- Clarify that timing alone does not equal causation.
- “Post Hoc Ergo Propter Hoc” style claim: Assumes that because one event follows another, the first caused the second.
- Watch for phrasing that skips evidence, e.g. "Assumes that because one event follows another, the first caused the second"
- Pattern hint: Observe that Event A happened before Event B.
Ask for controlled comparisons or additional evidence.
Post Hoc Ergo Propter Hoc is often mistaken for Correlation ≠ Causation, but the patterns differ. Compare the steps above to see why this fallacy misleads in its own way.
Close variations that are easy to confuse with Post Hoc Ergo Propter Hoc.
Frequently Asked Questions
Post Hoc Ergo Propter Hoc signals a weak reasoning pattern. Even if the conclusion is true, the path to it is unreliable and should be rebuilt with sound support.
Post Hoc Ergo Propter Hoc follows the pattern listed here, while Correlation ≠ Causation fails in a different way. Looking at the pattern helps choose the right diagnosis.
You will find it in everyday debates, opinion columns, marketing claims, and quick social posts—anywhere speed or emotion encourages shortcuts.
It can feel persuasive, but it remains logically weak. A careful version should replace the fallacious step with evidence or valid structure.