7 Answers

That that is, is. That that is not, is not. Is that it? It is.

>Jenn:    The movie that made this punctuation famous was Charly by Cliff Robertson in 1968. He won an Academy Award for this role.  He also played John F. Kennedy in PT109.

Charly is a 1968 American film directed by Ralph Nelson. The drama stars Cliff Robertson (in an Academy Award-winning performance), Claire Bloom, Lilia Skala, Leon Janney and Dick Van Patten and tells the story of a mentally challenged bakery worker who is the subject of an experiment to increase human intelligence. The movie was adapted by Stirling Silliphant from the novel Flowers for Algernon by Daniel Keyes.

Wow I have no idea.. I didnt ever realize it was in a movie.

That? That is. Is that, that? Is not. Is. Is not. Is that, that, it? it is.

Colleen

She did not say she peeked. She said she has experience with this because she teaches it to her students. That's what she meant by a "little" cheating, she knew from teacher's experience. Something the rest here do not have.

Eggplant, you were very close.  Let's see if I can make sense out of this.

The first "that" is known today as a determiner or demonstrative adjective as in "That book or that girl."

The second "that" is your ordinary pronoun.  Hence,

"That that is, is" simply means whatever it is, is (something like que sera sera), and so on.

That that is, is.  That that is not, is not.  Is that it?  It is.