"Reasonable Scientist" joke

Two guys are sitting in a quiet, rundown bar, when a man, dressed very sharply in a dark suit and carrying a briefcase, walks in. The two guys are surprised to see such a man in their local bar.
"He looks like a lawyer to me," the first guy says.
"No, I'd say an accountant," his friend replies.
After bickering back and forth, the first man decides to go over to the sharply dressed stranger to settle the debate.
"Pardon me," he says, "but my friend and I were having a disagreement over there and were wondering if you could help. Tell me, are you a lawyer or an accountant?"
"I'm neither a lawyer nor an accountant," replies the stranger. "I'm actually a reasonable scientist."
"What the hell is a reasonable scientist?" cries the man.
"Well, allow me to give you a demonstration. Do you have any goldfish?" asks the stranger.
The man nods.
"Well then, if you have goldfish it must be reasonable to assume that you keep them in either a tank or a pond," the stranger says.
"Why yes," replies the man, "I do keep them in a pond."
"Right," the reasonable scientist says. "Then if you have a pond it must also be reasonable to assume that you have a large house."
Once again, the man nods.
"And if you have a large house it must be reasonable to assume that you have a wife and children," says the reasonable scientist.
"Yes, I do," says the man in wonder.
"Right. And if you have a wife and kids you must have an adequate sex life."
"Right again," the man says. "At least three or four times a week."
"And if you're being serviced that often it is reasonable to assume that you don't masturbate on a regular basis," says the reasonable scientist.
"Hardly ever," the man admits.
"Precisely. So you see, by merely telling me that you have goldfish, I was able to deduce that you have a large house, a family and that you don't jerk off very often. And that, my friend, is the job of a reasonable scientist."
The man thanks him and returns to his friend.
"Well," says his friend, "is he a lawyer or an accountant?"
"Neither. He's a reasonable scientist," answers the man.
"What the hell is a reasonable scientist?" asks his friend.
"It's difficult to explain," replies the man. "Allow me to demonstrate. Do you have goldfish?"
"No," his friend replies.
"Well then, you must jerk off a lot!".