There was a man who sold spears and shields.
Holding one of his shields in hand, he cried, "My shields are so strong that nothing can pierce them." Then, he picked up one of his
spears and shouted, "My spears are so sharp that there Is nothing they cannot pierce." The
onlookers sniggered at him and one of them said, "So your spears are the sharpest and
your shields are the strongest. But what if one should use your spears to pierce your
shields?"
The man could give no answer.