“Leave the toys where they are,” Grandpa Song said gently. “Let us imagine one possibility. Suppose this spear could pierce this shield.” They kept their eyes on the untouched display.

Ahe thought slowly. Then this spear would be an exception. He could no longer say that no spear could pierce his shield. His first claim had left no room for an exception.

Nothing struck the shield, and no hole appeared. They were only following an idea. This would not prove that the spear could pierce every shield, but it would be enough to disprove his boast about this one.