Two builders (Dave and Stuart) are seated either side of a table in a pub when a well-dressed man enters, orders a beer and sits on a stool at the bar. The two builders start to speculate about the occupation of the suit

Dave: - I reckon he's an accountant.

Stuart: - No way - he's a stockbroker.

Dave: - He ain't no stockbroker! A stockbroker wouldn't come in here!

The argument repeats itself for some time until the volume of beer gets the better of Dave and he makes for the toilet. On entering the toilet he sees that the suit is standing at a urinal. Curiosity and the several beers get the better of him.

Dave: - 'Scuse me.... no offence meant, but me and me mate were wondering what you do for a living?

Suit: - No offence taken! I'm a Logical Scientist by profession

Dave: - Oh? What's that then?

Suit: - I'll try to explain by example ... Do you have a goldfish at home?

Dave: - Er .... mmm ... well yeah, I do as it happens!

Suit: - Well, it's logical that you keep it either in a bowl or in a pond. Which is it?

Dave: - It's in a pond!

Suit: - Well it's reasonable to suppose that you have a large garden then?

Dave: - As it happens, yes I have got a big garden.

Suit: - Well then it's logical to assume that, in this town, if you have a large garden then you have a large house?

Dave: - As it happens I've got a five bedroom house .... built it myself!

Suit: - Well given that you've built a five bedroom house it's logical to assume that you haven't built it just for yourself and that you are quite probably married? And with a family?
Dave: - Yes I am married, I live with my wife and four children.

Suit: - Well then it is logical to assume that you are sexually active with your wife on a regular basis?

Dave: - Yep! Five times a week!

Suit: - Well then it is logical to suggest that you don't masturbate very often?

Dave: - Do what? Not me, mate!

Suit: - Well there you are! That's logical science at work!

Dave: - How's that then?

Suit: - Well from finding out that you had a goldfish, I've told you about your sex life!

Dave: - I see! That's pretty impressive. Thanks mate!

Both leave the toilet and Dave returns to his mate.

Stuart: - I see the suit was in there. Did you ask him what he does?

Dave: - Yep! He's a logical scientist!

Stuart: - What's that then?

Dave: - I'll try and explain. Do you have a goldfish?

Stuart: - Nope.

Dave: - Well then, you're a wanker.