A Mathematician in Scotland

A passage I came across recently amused me and I wished to share:

A mathematician, a physicist, and an engineer are riding a train through Scotland.

The engineer looks out the window, sees a black sheep, and exclaims, "Hey! They've got black sheep in Scotland!"

The physicist looks out the window and corrects the engineer, "Strictly speaking, all we know is that there's at least one black sheep in Scotland."

The mathematician looks out the window and corrects the physicist, "Strictly speaking, all we know is that is that at least one side of one sheep is black in Scotland."

The above is a minor adaptation of a joke found in the novel The Curious Incident of the Dog in the Night-Time. I adapted it to fit my audience (I know a lot more physicits than logicians nowadays and so-called engineers to economist).