“This sentence is a lie” sounds false but is actually true. I think?
A description is “autological” if it describes itself. For example:
- “Short” is a short word, so it is autological.
- The phrase “excessively verbose, wordy, redundant, repetitious, repetitious, and prolix” also describes itself, so it too is autological.
- “Written in English” is written in English, so it is autological.
A description is “heterological” if it does not describe itself. For example:
- “Long” is not a long word; so it is heterological.
- “Bisyllabic” is not a bisyllabic word, so it is heterological.
- “Written in Arabic” is not written in Arabic, so it is heterological.
Now, is the word “heterological” itself heterological?
It’s not easy to say whether it is or not. This is something called the Liar Paradox and it has a surprising amount of potential solutions. That article linked explains it really well but, be warned, it is a bit dry.
The solution one of my professors gave that makes most sense to me is that, as a standalone sentence, “this sentence is a lie” is neither true nor false. At first glance the sentence makes sense and “lie” leads us to think that there is an untruth somewhere but there can’t be as there is no ‘truth value’ within it. That is to say that there is nothing in the sentence that can either be true or false therefore there is nothing that can be lied about.
Only one of many potential solutions so though. So, maybe?
