A physicist, a mathematician and a logician were travelling through the British Isles together.
Just after they had crossed the border into Scotland, they saw a black sheep in profile on the top of a hill.
The physicist remarked, “Look at that! All the sheep in Scotland must be black!”
The mathematician corrected him, “Not necessarily … all we can conclude is that at least one sheep in Scotland is black.”
The logician, however, had the last say. “You are both quite wrong,” he observed, “All we can really conclude is that at least one sheep in Scotland is black on at least one side!”