Each of Alan and Ben is a knight, a knave or a liar. (An explanation of the three types is given
here.)
Al says:
1. Ben and I do not have the same standard of veracity.
2. I never speak truthfully.
Ben says:
1. Al is not a liar.
2. I am not a liar.
Determine the type of each of Al and Ben.
A2 can only be a lie told by a knave.
And B2 must be true.
Since Al is a knave, B1 is true also.
Since B1 and B2 are both true, Ben is a knight.
Final Answer: Al is a knave and Ben is a knight.
And statement A1 is extraneous. Or, if you prefer, the puzzle can be solved with all the statements except B1. Or with all the statements except B2.
Edited on April 15, 2013, 6:11 pm
Too much Information (spoiler)
