Equivocation

Equivocation is when you use the same word to mean two different things in the same argument, so it sounds like a proof but it's a word trick. The argument looks valid because the word is repeated, but the meaning shifts. Once you notice the two senses, the inference no longer goes through. The fallacy is to rely on the ambiguity of a word to make an invalid step look valid. Clarifying the meaning in each use usually exposes the error.

Examples

• Only man is rational. No woman is a man. So no woman is rational.

• The end of life is death. The end of life is its purpose. So death is the purpose of life.

• Banks are by the river. Banks hold money. So the river holds money.