Equivocation is a logical fallacy that involves taking a word with more than one definition and freely substituting one definition for another.
- "A feather is light. Therefore, a feather cannot be dark."
- There are two meanings of the word light. The first sentence assumes a meaning that is the opposite of heavy, not the opposite of dark.
This fallacy is used frequently in the service of apologetics arguments. A few relevant examples:
- Atheism is based on faith.
- There are multiple meanings of the word faith, for example things you trust in without critical analysis or things which people believe with good evidence.
- The Bible is Metaphorically true.
- Metaphors are figurative language and as such aren't considered true or false. Declaring the Bible to be metaphorical allows one to assert the truth of the book without defending it. Subsequently those who use that argument slip back to the definition of true in the sense of reality after the calls to defend the Bible subside.
- "No true Scotsman" fallacy.
- When someone says, "That person wasn't really a Christian because he did that," they are relying on ambiguity in the word Christian and redefining it to suit their needs.
- The existence of laws implies a law-giver.
- Evolution is only a theory.
- This plays on the confusion between the scientific and colloquial definitions of the word theory.