An engineer, an experimental physicist, a theoretical physicist, and a philosopher were hiking through the hills of Scotland. Cresting the top of one hill, they see, on top of the next, a black sheep.
The engineer says: "What do you know, the sheep in Scotland are black."
"Well, some of the sheep in Scotland are black," replies the experimental physicist.
The theoretical physicist considers this for a moment and says "Well, at least one of the sheep in Scotland is black."
"Well," the philosopher responds, "on one side, anyway."
Attributed to William Knorpp. Found here.