I remember a similar joke from a book some years ago from the school: An engineer, a physicist and a mathematician are on a train crossing an unknown country.

I remember a similar joke from a book some years ago from the school: An engineer, a physicist and a mathematician are on a train crossing an unknown country. Suddenly, the engineer leaning out of the window says: "in this country the sheep are black!"; the physicist corrects: "in this region of the country, some sheep are black"; the mathematician limits himself saying: "at least from one of their sides."