An engineer, a lawyer, and a mathematician are traveling through England on a train. The engineer looks out the window at a passing farm and says “Look, the sheep in England are black”.
The lawyer promptly replies, “we do not have enough evidence to support your statement, all we can say is there is one black sheep in England”. The lawyer then leans back with a smug look on his face at finally having gotten back at the engineer for always using technical jargon and precise words.
The lawyer waited to see how his friend would respond. The engineer calmly looked at the mathematician and said “I believe this is your department”. To which the mathematician replied “strictly speaking you are both incorrect as all we can say is there exists at least one sheep that is black on at least one side in England”.