Just found a piece of scrap paper with only the sentence "This page intentionally left blank." If only they would insert the word "almost". It isn't blank. I looked up the quoted sentence and the search returned 26 million hits. I am not the first one to decide there is a little puzzle there: why call the page blank when it isn't?
The most important modern logician was Kurt Gödel (1906-1978). He was actually working in mathematics, but his work pertains to logical puzzles that go back to the Bible and beyond. A man says, "Anything a man says is false." Is the statement, made by a man, itself false?
I guess a publisher or a teacher might deflect questions if the page bears that sentence instead of being actually blank. In reading about blank pages that are not blank, I read explanations that tried to explain blank-but-not-blank with the words "such a page is devoid of content". Again, bending a little and inserting "important content" or maybe "relevant content" might help. Maybe not.
Sometimes puzzles like this are represented with pictures of a snake swallowing its own tail. One wonders how far the process can go on? The idea and the picture go back, again, to ancient times.
Just as quotation marks assist in my writing and communicating here, the idea of a different language has been used to try to separate the statement from discussion of it. Those quote marks are so handy that we have invented "air quotes", denoted by a gesture, to indicate which spoken words are being considered separately from what is being said about them.
I notice that comedians, politicians of more than one country, and speakers are pictured using air quotes. I suspect there there is, or will be, a doctoral dissertation on the invention, use and spread of the gesture that looks a bit like snake fangs to me.
