Quine's paradox

Quine's paradox is a paradox concerning truth values, attributed to W. V. O. Quine. It is a related problem to the liar paradox and uses indirect self-reference.

“Yields falsehood when preceded by its quotation” yields falsehood when preceded by its quotation.

What is the sentence talking about?

Let's take the step that the sentence implies.

it = “yields falsehood when preceded by its quotation”

its quotation = ““yields falsehood when preceded by its quotation””

it preceded by its quotation = ““yields falsehood when preceded by its quotation” yields falsehood when preceded by its quotation.”

We now have returned to the original case. So this sentence asserts:

“The sentence ““yields falsehood when preceded by its quotation” yields falsehood when preceded by its quotation.” is false.”

In other words, the sentence says that it is false. This is a paradox: If it's true, it's false, and if it's false, it's true.

See also

• Quine's modal paradox