There is an island of people who all have green eyes. However, they don’t know they have green eyes because they have been imprisoned on this island since birth. They can see each other, but the can’t see themselves. There are no mirrors, and they’re not allowed to speak to each other.
On this island, all green-eyed people are allowed to leave, but only under dangerous circumstances — they have to go alone, at night, to a guard booth, where the guard will examine eye color and either let the person go (green eyes) or throw them in the volcano (non-green eyes).
So, of course, everyone should be free to leave, but they just need to realize they all have green eyes.
Let’s say you got the chance to visit the island and address the people. You can only say one sentence, and it can’t be new information. What do you say to free everyone?
Watch the video below for the answer.