# Affirming the consequent

*Also called: Converse error*

- **Cluster:** Broken structure — The form itself does not carry the conclusion
- **Page:** https://fallacy.wiki/fallacy/affirming-consequent/
- **In Arabic:** https://fallacy.wiki/ar/fallacy/affirming-consequent.md
- **Licence:** CC BY 4.0 — https://creativecommons.org/licenses/by/4.0/

## What it is

From if A then B, and B is true, wrongly concluding A. Other causes of B are ignored.

## In the wild

> If it rains the road is wet; the road is wet, so it rained.

## How to answer it

Name one other thing that would produce the same result.

## Origin and naming

Named for its shape: the consequent — the 'then' half of a conditional — is affirmed, and from that the 'if' half is concluded. It is the invalid twin of modus ponens, one of the two ways a hypothetical syllogism can misfire.

## More places it shows up

- If the servers are overloaded the site is slow; the site is slow this morning, so the servers must be overloaded — and nobody checks the office internet.
- Candidates who bluff get caught in interviews; this candidate was caught, so he must have been bluffing.
- If the new feature worked, users would upgrade; users upgraded, so the feature works.
- When the price drops, demand rises; demand rose last quarter, so the price drop did it.

## How to spot it

- Notice when the shape is 'if cause then effect; effect happened; so cause happened' — ask what else produces that effect.
- Notice when the argument never asks whether the stated condition was the only path to the result.
- Notice when swapping the explanation for another plausible one leaves the premises just as true.

## Nearby

- [Denying the antecedent](https://fallacy.wiki/fallacy/denying-antecedent.md)
- [Post hoc ergo propter hoc](https://fallacy.wiki/fallacy/post-hoc.md)
- [Masked man fallacy](https://fallacy.wiki/fallacy/masked-man.md)
- [Affirming a disjunct](https://fallacy.wiki/fallacy/affirming-disjunct.md)

## Read more

- [Wikipedia](https://en.wikipedia.org/wiki/Affirming_the_consequent)
- [Wikipedia: Formal fallacy](https://en.wikipedia.org/wiki/Formal_fallacy)

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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.