On an island far away are 100 serfs and their wicked lord. 50 of the serfs have green eyes; the rest have blue eyes. Being uber-logical beings, the serfs have little problem identifying others’ eyes as either green or blue. However, none of the serfs knows his own eye color. If this weren’t frustrating enough for the serfs - all of whom were very talkative in college (the economy crashed; what were they to do besides serfing?) - the lord has carefully selected his serfs from 100 different faraway lands so that the serfs have no way of communicating with one another. (As the lord would have it, this inability to communicate precludes any opportunity for mutinous collusion.)
On a particular summer day, after having knocked back a few Red Stripes, the lord makes a generous gesture toward his workers, who do understand what the lord says to them.
“Starting tonight at 7 o’clock, and at 7 o’clock every night from now on, a yacht will head from this island to a free land. If you can tell the yacht’s captain the true color of your eyes, you are free to embark. But be warned: if you tell him incorrectly the color of your eyes, he will feed you to the sharks, as I have ordered him to do!
“Oh, and one more thing,” says the lord at the end of his speech. “At least one of you has green eyes.”
Which of the serfs makes it to the free land, and when?