Try to Free the Island in this Classic Logic Puzzle
An island full of 100 logicians have become trapped under the wrath of an evil dictator. (Why logicians would get themselves into a position in the first place, we'll never know.) Each day, the island prisoners get one opportunity to approach the guard and ask to leave. They can only leave if they have green eyes. If they don't have green eyes, they'll die an immediate and painful death.
Here's the catch: all the logicians have green eyes. However, there's no clear reflective surfaces for the logicians to see their eye color.
You, as an ambassador, want to help the trapped logicians. The tyrant graciously gives you one sentence and one sentence only to say to them. He gives you one stipulation: you cannot tell the logicians any new information.
So what do you say to the trapped islanders to make them realize they have green eyes?
This logic puzzle about the power of phrasing comes courtesy of TED-Ed on YouTube.