# Post hoc ergo propter hoc

*Also called: After this, therefore because of this*

- **Cluster:** Causal errors — Sequence, coincidence and hindsight read as cause
- **Page:** https://fallacy.wiki/fallacy/post-hoc/
- **In Arabic:** https://fallacy.wiki/ar/fallacy/post-hoc.md
- **Licence:** CC BY 4.0 — https://creativecommons.org/licenses/by/4.0/

## What it is

Treating sequence as causation, so whatever came first is taken to have caused what followed.

## In the wild

> Sales rose after the rebrand, so the rebrand caused it.

## How to answer it

Ask what else changed in the same period, and what sales did before.

## Origin and naming

From the Latin 'post hoc ergo propter hoc', 'after this, therefore because of this'. The phrase fossilizes one of the oldest mistakes in reasoning: letting the calendar stand in for a mechanism. It is the template from which most causal fallacies are cut.

## More places it shows up

- Ever since we switched to the new coffee supplier, people have been calling in sick less. Good call on the coffee.
- I updated my phone and now the battery drains fast — the update broke it.
- The city's accident rate dropped the month the new mayor took office; his leadership is clearly working.
- Two days after I started the herbal supplements, my headaches stopped. They work.

## How to spot it

- The argument leans on a timeline: 'first X, then Y' is offered as the whole case.
- No mechanism is proposed — nothing about how X would actually produce Y.
- Ask 'what else happened around the same time?' and the answer turns out to be a lot.

## Nearby

- [Correlation implies causation](https://fallacy.wiki/fallacy/correlation-causation.md)
- [Fallacy of the single cause](https://fallacy.wiki/fallacy/single-cause.md)
- [Regression fallacy](https://fallacy.wiki/fallacy/regression.md)

## Read more

- [Wikipedia](https://en.wikipedia.org/wiki/Post_hoc_ergo_propter_hoc)
- [The Fallacy Files](https://www.fallacyfiles.org/posthocf.html)

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From fallacy.wiki — a bilingual field guide to 91 logical fallacies, published by phi holdings. Licensed CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/): reuse freely with attribution to fallacy.wiki.