Will 2020 See The Extinction Of The Red-eyed Monks?

For those of you not familiar with what has been called “the hardest logic puzzle in the world”A, The Blue-eyed Monk problem or Blue-eyed Islander problem (Version 2), check out the above reference links. For what it’s worth, that “hardest” title is probably an exaggeration. But my new version, inspired by recent events, might be harder.

In this version of the famous logic problem, there are a number of monks on this remote island. All of them are “perfect logicians”. Every monk sees every other monk every day, but they are rugged individualists who never talk to each other or communicate in any way. But they also take full responsibility for their actions and obey all rules and protocols (yes, this problem is entirely fictional). Strangely, there are no mirrors or reflective surfaces on the island. The ferry visits the island every night to drop off supplies and would take the monks to the mainland, if necessary. But none of the islanders wants to leave and no strangers are allowed on the island. In this version of the problem, all of the monks have red eyes.

One day, almost all of the monks noticed that one of their peers had blue eyes, but they all continue to go about their lives. Many days later, it is noticed (by almost all of them) that two of the monks now have blue eyes. Still, life goes on. This trend continues with a slowly increasing frequency until many, many days later, the first monk to have developed blue eyes is found dead. Doctors on the mainland soon discover that some as-yet-unknown, but contagious pathogen hit the island and the number of monks infected has been growing 2% every day for quite some time. The only visible symptom is the changing of eye color from red to blue. (No other eye color is affected.) The disease is not contagious until the eyes go blue but then remains contagious until the infected person dies. How it spreads is still unknown, but obviously, direct contact or even close proximity is not required. By the time the doctors figure all of this out, red-eyed monks have started changing eye color at the rate of one every other day and the second blue-eyed monk has just died. If a blue-eyed monk gets to the mainland in time, they can be cured, but the ferry does have a limited capacity. The monks are pacifists, so there will be no shooting of blue-eyed monks (yes, I might have a personal stake in this directive). All of this information was left on a large sign at the ferry dock the next day.

So what do the monks do? Will they go extinct? Will 2020 see the end of all logical thought on this planet? Only you can answer that question. Good luck! Leave your answers in the comment section below.

To see the Note click here.To hide the Note click here.
In the interest of full disclosure and transparency, I have addressed this problem before. After much fumbling, I did come up with a better (faster) solution, which was widely regarded as cheating (see comment to “The Blue-spotted Monks Revisited”.