There is an island filled with grass and trees and plants. The only inhabitants are 100 lions and 1 sheep.
The lions are special:
- They are infinitely logical, smart, and completely aware of their surroundings
- They can survive by just eating grass (and there is an infinite amount of grass on the island)
- They prefer of course to eat the sheep
- Their only food options are grass or sheep
Now, here’s the kicker:
- If a lion eats a sheep he TURNS into a sheep (and could then be eaten by other lions)
- A lion would rather eat grass all his life than be eaten by another lion (after he turned into a sheep)
You can make the following assumptions:
- Assume that one lion is closest to the sheep and will get to it before all others. Assume that there is never an issue with who gets to the sheep first. The issue is whether the first lion will get eaten by other lions afterwards or not
- The sheep cannot get away from the lion if the lion decides to eat it
- Do not assume anything that hasn’t been stated above
Will that one sheep get eaten or not and why?
The sheep will survive.
If there were 1 lion and 1 sheep, then the lion would simply eat the sheep. The sheep will not survive.
If there were 2 lions and 1 sheep, then no lion would eat the sheep, because if one of them would, it would surely be eaten by the other lion afterwards. The sheep will survive.
If there were 3 lions and 1 sheep, then one of the lions could safely eat the sheep, because it would turn into the scenario with 2 lions, where no one can eat the sheep. The sheep will not survive.
If there were 4 lions and 1 sheep, then no lion would eat the sheep, because it would turn into the scenario with 3 lions. The sheep will survive.
Continuing this argument, the conclusion is as follows:
- If there is an even number of lions, then nothing happens and the sheep survives.
- If there is an odd number of lions, then any lion could safely eat the sheep and the sheep will not survive.
This is similar to the Unexpected Hanging Paradox.