One day you meet three persons, each either a Knight or a Liar. You ask "How many of you are knights?", and the first person answers "Grok!".
Not understanding, you ask the second one "What does 'Grok' mean?", and he answers "One", but then the third one cries out "That's false!".
What can you tell about each person, if anything?
Let the first, second and third person be respectively denoted by A, B and C. Now, C's statement implies that B is a liar. Since no liar will ever truthfully identify a fellow liar, it follows that C is a knight,so that B is a liar.
If A is a knight, then A has truthfully identified the total number of knights as 2, and accordingly, "grok" will mean "two" in that situation.
If A is a liar, then "grok" can either mean mean either of the numbers "zero" or "three". It is also possible that"grok" do not represent numbers, but can represent any given thing. For example, "grok" can denote the name of a person/place etc.
Consequently, summarising we have:
* Second Person... Liar
* Third Person ... Knight
* First Person....Knight or Liar.
* "grok" means "two" iff the First Person is a Knight.
Edited on June 30, 2007, 2:57 pm