On the eve of a great battle, Miyamoto Musashi noticed that the Daimyo (samurai lord) with whom he had taken service seemed unable to focus on the impending battle. Asked what was the matter, the daimyo told Musashi that an astrologer had predicted that he, the daimyo, would soon die.
Shocked by this, Musashi called for the astrologer in the daimyo's presence. When the astrologer presented himself, Musashi questioned the wizard. "Where do you get this information that our lord will soon die?" Musashi asked.
"All is written in the stars," the astrologer answered cryptically. "And when do the stars say you will die?" Musashi asked. "The stars predict that I will live a long life, find fame and fortune, and have many offspring!" the wizard proclaimed confidently.
At this point, Musashi's sword separated the wizard's head from his shoulders. Placing the head of the astrologer at the feet of the shocked daimyo, Musashi explained to the samurai lord: "If a man is unable to predict his own fate, what hope has he predicting the fate of others?"