The Greek Philosophers Thought Puzzle

The puzzle

One day three Greek philosophers settled under the shade of an olive tree, opened a bottle of Retsina, and began a lengthy discussion of the Fundamental Ontological Question: Why does anything exist?

After a while, they began to ramble. Then, one by one, they fell asleep.

While the men slept, three owls, one above each philosopher, completed their digestive process, dropped a present on each philosopher’s forehead, the flew off with a noisy “hoot.”

Perhaps the hoot awakened the philosophers. As soon as they looked at each other, all three began, simultaneously, to laugh. Then, one of them abruptly stopped laughing. Why?

Hint

The one who stopped laughing, asked himself what the other philosophers were seeing that made them laugh.

Solution

If he (the smartest philosopher) had nothing on his head, then he realized that the second smartest philosopher would have quickly worked out that the third smartest was laughing only at the second smartest philosopher, and thus the second smartest philosopher would have stopped laughing.