Affirming the consequent
Affirming the consequent, sometimes also called asserting the consequent or the converse error, is a type of logical fallacy where a premise is asserted as true simply because a conclusion implied by the premise is true. This is a fallacy because it assumes that the conclusion could only have been reached in one particular way.
- If an animal is a rat, then it has four legs
- My dog Lassie has four legs
- Therefore, Lassie is a rat
- A implies B
- Therefore, A
- Creationism example 1
- If the universe was created by God, then there would be order and natural laws observed in the universe
- We see examples of order and natural laws in the universe
- Therefore, the universe was created by God
This argument assumes that a deity is the one and only explanation for order in the universe. And even if we do assume that a deity is the only explanation, it doesn't automatically mean that it must be the Christian deity. The Flying Spaghetti Monster is a good counter-example that satirically exposes the underlying fallacy of this argument.
- Creationism example 2
- If the Biblical flood story is true, then there was a boat built with the dimensions described in the Bible
- We found a boat with these dimensions
- Therefore, the Biblical flood story is true.
To see why this is a fallacy, consider the same logic applied to the story of Cinderella and the existence of Cinderella's castle in Disneyland.