If the sentence is true, then it is a lie as it says. But if it is a lie, it cannot be true. A lie cannot also be a truth. So the sentence being true makes it a lie.
On the other hand, if the sentence is a lie, then it is not as it says: it is true. But that is just what the sentence says, which makes the content of the sentence true. So the sentence being a lie makes it true.
This paradox is not just true in English, but in any language powerful enough for a sentence to make a claim about itself. This is true of mathematics as well. Paradox can never be removed from any symbol system that makes claims about itself.
Another example is the statement that "there is no cabal". Only a cabal can know if there is no cabal, so this is either a guess, or, it is a cabal trying to pretend it does not exist.
Not all paradoxes are true logical paradoxes, since they can also be common-sense-defying statements that appear true. Some famous examples of this kind of paradox include:
A paradox can also arise in ethics. Assuming power over others may sometimes be required to protect them while diminishing their right to autonomy. This is defined as an ethical dilemma, which means "a paradox arising in ethics". Similarly, an ethical dilemma may be resolved by re-framing of the problem to reveal the false contradiction.
Because a paradox forces one to think "out of the box" about possibilities other than true or false in logic, right or wrong in morality, it is often brought up for educational purposes. People who do not see a paradox where others do are likely to be too certain that they are right.
- "The Definitive Glossary of Higher Mathematical Jargon". Math Vault. 2019-08-01. Retrieved 2020-10-08.
- "Definition of PARADOX". www.merriam-webster.com. Retrieved 2020-10-08.