Enthymemes...hmm?

Enthymemes: These are a lot like syllogisms, but used in rhetoric, and not in scientific circles. "The premises used in construction rhetorical proofs differ from those used in dialectic and science only in the degree of certainty we can attach to them...Rhetors ordinarily use some widely held community belief as the major premise of their argument. Then they apply that premise to the particular case in which they are interested."

So...homework question number 3, p. 186:

Popular slogans are conclusions or premises of enthymemes, as stated in the book.  "Elvis has left the building"=part of a long argument whose other premises are never stated...I must articulate them...

Originally, the phrase was used to alert concert-goers of Elvis' departure from the premises, thus dashing their hopes of an encore performance.  Then, it was thrown into popular culture through lps and other records.  It then made its way into movies and such popular media, eventually being turned into a fairly common statement used in TV shows.  

The meaning now is basically "the show is over, go home".

I'm not sure exactly how to start this, but anyways...

X=...

Y is an example/reason of/for X

Therefore, it follows that Z

I will use this statement to mean that the show is over (show being anything from TV to live event).  

The show is over.

The main person in the show is no longer here, and there is nothing else to see.

Please leave.

Thus, Elvis has left the building.