During the French Revolution three men -- a priest, a doctor, and an engineer -- were condemned to die and were led to the guillotine.
The priest went first. Asked whether he preferred to face up or down, the priest replied, "I will face my God"; and he was so placed in the terrible machine. The release was tripped, but - merveille - the blade did not fall. In accordance with the law at the time, the priest was set free.
The doctor was well used to the sight of blood but the sight of the guillotine horrified him. He therefore chose to face downwards at his moment of truth. Again the release was tripped -- and, again, the blade remained where it was. So the doctor too was given his liberty.
The engineer approached the guillotine in a pensive mood. "And you, monsieur, do you prefer face up or face down? Monsieur?" "Oh, I beg your pardon... face up, s'il vous plaît."
And so he assumed the position. But a moment before the executioner was to release the blade, the engineer shouted, "Wait! Wait! Stop! I think I see what your problem is!"