Post Hoc Fallacy
Also known as: Post Hoc Ergo Propter Hoc, False Cause, Correlation vs Causation
What is Post Hoc?
Post hoc ergo propter hoc (Latin for 'after this, therefore because of this') is a fallacy that assumes a causal relationship between two events simply because one occurred before the other. The temporal sequence of events — A happened, then B happened — is treated as proof that A caused B. However, correlation in time does not establish causation. The events may be coincidental, or both may be caused by a third factor.
Example
A company launches a new marketing campaign and sees increased sales the following month.
“Sales went up right after we launched the campaign, so the campaign must be the reason.”
While the campaign might have contributed to increased sales, the timing alone does not prove causation. Seasonal buying patterns, a competitor going out of business, or a viral social media post could all have contributed. Establishing causation requires controlled analysis, not just sequence.
How to Spot It
- Two events are connected solely because one happened before the other.
- No mechanism or controlled evidence is offered to explain why A caused B.
- Alternative explanations for B are not considered.
- The argument relies on 'right after' or 'ever since' as the primary evidence of causation.
How to Counter It
- Ask what specific mechanism connects the two events beyond timing.
- Present alternative explanations that could account for the second event.
- Cite examples where the same first event did not lead to the same outcome.
- Suggest controlled experiments or data analysis to test the causal claim.
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