In ancient times, an old man living near the northern frontier lost his horse, which ran away beyond the Great Wall into the land of the northern tribes. His neighbors comforted him, but he calmly said, "This may not necessarily be a bad thing."

A few days later, the lost horse returned, bringing several fine tribal horses with it. The old man then said, "This may not necessarily be a good thing."

Indeed, his son, who loved to ride, broke his leg after falling off one of the new, spirited horses. The neighbors again offered sympathy, but the old man calmly remarked, "This may not necessarily be a misfortune."

Soon after, a war broke out, and all able-bodied young men were conscripted into the army. Because the old man's son was lame, he was exempted from military service, thus avoiding the dangers of war.