The logician, somewhat baffled at the man’s comment, decides to educate him in the basics of logic. “Well, it’s simple reasoning. You take a fact and draw other facts from it, like… Do you own a lawnmower?”
“Uh, yeah? So?”
“Well then, logically, you must own a lawn, correct?”
“Well, yeah.”
“If you have a lawn, then I must logically assume you have a house to go with it.”
“Yeah, that’s right!”
“And a house would be too big for one man, so am I right in assuming you have a wife? Kids, perhaps?”
“I do! Two kids, a third on the way!”
“Then logically, you must be straight. And it goes on like that, you see? Logic.”
“That’s incredible! I’ve gotta tell my buddies about this!”
The logician is again baffled that the man’s friends don’t know what logic is either, but thinks little of it as he watches the man leave.
That evening, the man approaches his friend and says “Hey, have you heard about this thing called logic?”
“What the hell is that?”
“Okay, so it goes like this: Do you own a lawnmower?”
“No?”
“That means you’re gay.”
This is an old Norm Macdonald bit, except he starts with a dog house, not a lawnmower.
I first heard it as lawnmower. And either way, it’s more about the structure than about getting every word right. If nobody could put their own spin on existing jokes, we never would have gotten Norm’s version of the moth joke.