A Variation

A historian, a scientist, and a mathematician are sharing a cabin on a train traveling through Scotland. The train suddenly stops, and the conductor announces that the train will be delayed for some time, so they talk to pass the time. As the historian glances out the window, he notices a lone black sheep standing in a field. "Ah, all Scottish sheep are black," he exclaims. The scientist corrects him. "No," she says, "it is far more likely that some Scottish sheep are black, and others are white." They both naturally turn to the mathematician, who silently contemplates the sheep for some time. Eventually, he says, "In this particular field, on this particular day, at this particular time, there exists one sheep that is at least half black."

Meanwhile, a priest walks by, and the group inquires his opinion on the matter. The priest replies, "All Scottish sheep are white, that black one is a forgery made by the devil."

---

Plus: a bonus fallacious proof of the existence of unicorns:

Einstein showed that space and time are closely related.
There was no space before the universe existed.
Thus, there was no time before the universe existed.
Space is infinite.
Therefore, time is also infinite.
Thus, time has always existed.
Thus, before the big bang, time both existed, and didn't exist.
Therefore, if something exists, it also doesn't exist.
Unicorns don't exist.
Thus, unicorns exist.
QED