You know that the negation of a true statement is a false statement, and the negation of a false statement is a true statement. You also know that you can negate a sentence by preceding it with “It is not true that ….”
Now look at the following statement and its negation, invented by David Bernstein. Which one is true?
- This sentence contains five words.
- It is not true that this sentence contains five words.
How about this pair?
- This sentence contains ten words.
- It is not true that this sentence contains ten words.