Newt Gingrich is on an airplane, flying back to DC. The guy sitting next to him is immersed in a book and pays no attention to Newt. Toward the end of the flight Newt asks:

Newt: "What book is that you're reading?" 
Man:  "It's called 'Deductive Reasoning"
Newt: "Sounds interesting, what's it about?" 
Man:  "Let me give you an example."
Newt: "Okay."
Man:  "Do you have a dog?"
Newt: "Yes, I do, as a matter of fact."
Man:  "I would deduce from this, then, that you have a yard
       as well, no?" 
Newt: "Yes!  I do have a yard." 
Man:  "Then I would further deduce that you have a house next
       to this yard?" 
Newt: "I do!"
Man: "Then I'll bet you have a family, don't you?"
Newt: "Yes, a very nice family!" 
Man:  "And you're a heterosexual, aren't you?"
Newt: "You betcha!  I'm beginning to see how this works!"

Later that week, Newt goes out and buys the book on
deductive reasoning and is determined to read it cover
to cover on his return flight. His plane takes off and
he begins reading.  Two hours later, the man sitting
next to him notices how Newt is so engrossed in this
book, and just can't keep himself from being impolite
and interrupting:

Man:  "Excuse me, sir, what's that you're reading?" 
Newt: "It's called, 'Deductive Reasoning'."
Man:  "Oh.  Then you must have learned how to use deductive
       reasoning, eh?"
Newt: "Well, yes, as a matter of fact I have.  Let me show
       you how it works." 
Man:  "Okay." 
Newt: "Do you have a dog?" 
Man:  "No." 
Newt: "Well, then, you must be a homosexual!"