Table of Contents

## Can a brother give the same answer to the same question?

The interesting thing is that each brother will give the same answer to the same question. For example, suppose you ask whether two plus two equals four. The accurate truth teller knows that it is and will truthfully answer yes.

## What happens if you ask twin brothers which is true?

Suppose there are twin brothers, one which always tells the truth and one which always lies. (So in this case they both know what is true and false, or as you put it, both are accurate in their knowledge.) What one yes-no question could you ask to either one of the brothers to figure out which one he is?

## What happens if you ask your brother if he always tells the truth?

The question one could ask is, “If I were to ask your brother whether you always tell the truth, what would he say?” A reply of “no” means you are talking to the truth teller, a reply of “yes” means you are talking to the liar. Another possible question is, “If I were to ask you whether you always tell the truth, what would you say?”

## Can a lying brother give the same answer?

The lying brother is totally inaccurate in his beliefs; all true propositions he believes to be false, and all false propositions he believes to be true. The interesting thing is that each brother will give the same answer to the same question.

The interesting thing is that each brother will give the same answer to the same question. For example, suppose you ask whether two plus two equals four. The accurate truth teller knows that it is and will truthfully answer yes.

Suppose there are twin brothers, one which always tells the truth and one which always lies. (So in this case they both know what is true and false, or as you put it, both are accurate in their knowledge.) What one yes-no question could you ask to either one of the brothers to figure out which one he is?

The question one could ask is, “If I were to ask your brother whether you always tell the truth, what would he say?” A reply of “no” means you are talking to the truth teller, a reply of “yes” means you are talking to the liar. Another possible question is, “If I were to ask you whether you always tell the truth, what would you say?”

The lying brother is totally inaccurate in his beliefs; all true propositions he believes to be false, and all false propositions he believes to be true. The interesting thing is that each brother will give the same answer to the same question.