=== From http://folklore.usc.edu/professor-of-logic-joke/
This guy Chuck goes over to his neighbor, who’s just moved in. He tells him the usual,
“Hi, just wanted to welcome you to the neighborhood, what’s your name?”
The guy’s like “Hi, I’m Jerry.”
Eventually they get to what they do. Chuck goes “I’m a plumber.”
The other guy says he’s a professor of logic at a university.
Chuck asks him,
“What do you teach?”
“I’m a professor of logic.”
“What do you mean by that?”
And the professor says,
“Let me give you an example. Do you have a doghouse?”
“Well, then I’d assume you have a dog.”
“Well, you know, when dogs have dog houses, and they live in them, that means you have a few kids, and it’s theirs and they take care of it.”
“I do have kids. Two of ‘em actually.”
“Alright, you got kids. That usually means you’re married. To a woman, in most cases.”
“Yeah, I’m married to a woman.
“Well, then you’re a heterosexual male.”
“I am, that’s right.”
“Now you see. Just by asking you if you have a doghouse, I was able to determine you’re a heterosexual male.”
Chuck just goes, “Wow! That’s unbelievable.” And he leaves, impressed.
The next day, our guy Chuck, the main one, not the professor, he’s hustling to get to the bus stop.
So, he gets there. Sees this guy next to him, he asks him if the bus has already come.
“No, it hasn’t.”
Chuck says oh, guess we’ll just have to wait a few minutes, then.
And, uh, the other guy lights up a cigarette and jokingly says “As soon as I light this cigarette, I bet the bus is gonna show up.”
Sure enough, he lights it, and the bus comes around the corner.
Chuck, amazed again, asks him if he’s a professor of logic. The guy with the cigarette doesn’t know what that means, he asks Chuck to explain.
Chuck doesn’t quite know how, and he says,
“Here, let me give you an example.”
“You have a doghouse?”
“Oh, you must be one of them gays!”