Re: Another Paradox
I already got Hint #1.
Hint #2.....doesn't make any sense. If the judge tells him that he will be hung Monday....then he already knows when it will happen. Then the judge tells him that he won't know it until the hangman arrives at noon.....but the judge already told him, so he already knows. How could he not know it until the hangman arrives at noon? He also said the hangman would arrive in the morning. Noon is not morning anymore, is it? The judge seems to be aliar or contradicting himself, which leaves the prisoner to go free. No?
Or, did I not get the problem again? If so....what is the problem?
Hints #1 and #2 are things I found on Google which are not actually part of the problem. I added them in because I thought they were illuminating. You used Hint #2 to show the judge was lying but the judge never actually says the words of Hint #2 so there is no lie there. Also your comments about noon not being morning have
NOTHING to do with the problem. The judge says the following,
"The hanging will take place at noon," said the judge to the prisoner. on one of the five weekdays of next week, but you will not know which day it is until you are so informed on the morning of the day of the hanging." There are two clauses to his sentence; the prisoner is to be notified in the morning and then to be hung at noon. There is no lie there either.
The idea behind solving the problem is not just to look through the text and try and find items the judge said which might qualify as lies.
This is an intelligent approach to solving the problem but the concepts which arise in formulating the problem do not really center around this approach.
ONE OF THE KEY PARAMETERS WE ARE GIVEN IN THE PROBLEM IS THAT THE JUDGE ALWAYS TELLS THE TRUTH. HE WILL NEVER
KNOWINGLY LIE. Both of your solutions, yesterday and today focus on finding lies stated by the judge. Finding possible lies by the judge is not really what the problem is about.
WHAT THE PROBLEM IS ADDRESSING IS TO FIND A SITUATION WHERE THE CONDITIONS OF THE PROBLEM, AS STATED, CANNOT BE CARRIED OUT THUS FORCING ONE OR MORE OF THE JUDGE'S STATEMENTS TO BECOME LIES, even though the judge never intended them to be lies.
Also, we are looking for why the lawyer's seemingly impeccable logic does not work out and in fact leads to an illogic which MAKES a liar out of the judge .
What happens is that if the prisoner makes it past noon on Thursday and is not hung, then and only then, he can deduce that the hanging is set for Friday and he can demand to be released. At this exact moment, the judge's decree is violated and the sentence, as stated, can't be carried out. TO CARRY OUT THE SENTENCE ON FRIDAY WOULD INADVERTENTLY MAKE A LIAR OUT OF THE JUDGE AND RELEASING THE PRISONER ALSO MAKES A LIAR OUT OF THE JUDGE. Therefore, we have a paradox. An honest judge is made a liar but only if the hanging is scheduled on Friday, the last possible day.
The other item being examined is the problem of why the lawyer's seemingly impeccable logic leads to the conclusion that the hanging can never occur per the judge's decree. This conclusion proves to be false if the hanging is set for any day except Friday. The lawyer took the fact that Friday was eliminated and worked backwards through the earlier days all the way to Monday, showing that those days were not possible either.
THE LAWYER'S LOGIC IN WORKING BACKWARDS LOOKS A LITTLE SUSPECT BUT TRY AS WE MIGHT, WE CAN NOT REALLY SEE ANY APPARENT ERROR IN IT. We are looking for the error in the lawyer's logic. There has to be an error because the sentence put forth by the judges fails to be doable in certain instances.
It turns out that the error made by the lawyer exists but it is subtle and hard to see, even when it is pointed out to people. It goes against the grain of our intuition.
The lawyer's error has to do with the fact that if noon passes on Thursday, then Friday must be the day. The prisoner knows that for certain which violates the judge's decree. The judge's decree can not be carried out.
So Friday can be eliminated after noon passes on Thursday without a hanging. NOW THAT THIS IS ESTABLISHED, THE LAWYER MAKES HIS MISTAKE, HE SAYS "WE CAN NOW ELIMINATE FRIDAY FOR ALL CASES. THIS IMPLIES THAT WE DON'T HAVE TO WAIT UNTIL 1 MINUTE AFTER NOON ON THURSDAY, WE CAN REASON THAT PRISON MANAGEMENT SIMPLY WILL NEVER USE FRIDAY AS THE HANGING DAY."
This sounds totally reasonable. It is hard to find fault with it. Since Friday causes a problem, prison management just won't ever schedule the hanging for Friday. Therefore Thursday is the actual last day for the hanging. At this point we have gone down the tubes, the lawyer is no longer making sense. Why? Because the same argument can now be used to eliminate Thursday, then Wednesday, Tuesday and finally Monday. The lawyer then arrives at the erroneous conclusion that the sentence can't be carried out on any day of the week because the prisoner will already know about it therefore the prisoner will not be hanged.
THE ERROR IN LOGIC -
The lawyer's error occurs as follows: He states that if Thursday at noon passes and the prisoner is still alive, the judge's decree can't be carried out. THIS IS TRUE - SO FAR SO GOOD. Now the lawyer takes the fatal step and declares that Friday can be eliminated in the general case, the prisoner does not have to wait until just after noon on Thursday to know that Friday is out. The prisoner has deduced that Friday simply can't be used as the last day. When that deduction is accepted as true, the lawyer's entire line of reasoning fails.
SIDEBAR - Trying to explain something like this as clearly as possible and in as few words as possible leads to the explainer gaining more understanding of the problem himself.
Lakey