Here is a (slightly shortened) joke from the book *The Curious Incident of The Dog in the Night-Time:*

There are three men on a train. One of them is an economist and one of them is a logician and one of them is a mathematician. And they have just crossed the border into Scotland and they see a brown cow standing in a field from the window of the train.

And the economist says, "Look, the cows in Scotland are brown."

And the logician says, "No. there are cows in Scotland of which one at least is brown."

And the mathematician says, "No. there is at least one cow in Scotland, of which one side appears to be brown."

I found this page looking for a joke much like these but with a philosopher,a mathematician and a logician who encounter sheep while riding a train in Scotland.They comment on the color,each observation being obviously limited by the constraints of their thought systems.Do you know that one?It is a teaching tool I wish my son to encounter.

For especially nerdy people, I tell the fence joke where the goal is simply to enclose a fixed number of sheep with a minimal amount of fence. The engineer builds a circle and the physicist encloses the convex hull of the sheep with the sheep packed into as tight a circle as possible, thus saving a foot or so off the engineer's design.