In an island peopled by Knights (who always say the truth) and Liars (who obviously always lie), two persons spoke about each other.
A said: "B would say I lie."
B said: "That is true."
Can anything be deduced as to what kind is each of them?
(In reply to Answer
by K Sengupta)
Assume that A is a Knight, then it follows that B would indeed accuse A of being a liar. Accordingly, B's statement would be false in that situatuation, so that B would be a liar.
Assume that A is a liar. Then, it follows from A's false statement
that B would in reality, say that A is not a liar. But, this is false
since at the outset, we have assumed that A is a liar. Consequently, B is a liar.
Comparing the two cases , it follows that B is a liar. Now, a Liar
will always identify a fellow Liar as Knight and will identify a
Knight as a Liar. Since, B has identified A's statement as a truthful one , it now follows that B must be a liar.