| Title: | Mathematics at DEC |
| Moderator: | RUSURE::EDP |
| Created: | Mon Feb 03 1986 |
| Last Modified: | Fri Jun 06 1997 |
| Last Successful Update: | Fri Jun 06 1997 |
| Number of topics: | 2083 |
| Total number of notes: | 14613 |
I'm looking for reference to the paradox about the prisoner that is thrown in jail and told that if he guesses what day he is planned to be executed, he will be set free. He performs some supposedly logical reasoning, and guesses wrong anyway. Can anyone point me to a note previously written in this conference, or merely recite the puzzle ? Thanks. /Eric
| T.R | Title | User | Personal Name | Date | Lines |
|---|---|---|---|---|---|
| 805.1 | CLT::GILBERT | Builder | Thu Dec 17 1987 16:08 | 5 | |
A prison is told he will be executed "some morning next week",
and if he guesses the right morning (sometime before that morning),
then he'll be set free. I assume he's allotted only one guess.
Days are Monday thru Friday (sorry, no executions on weekends).
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| 805.2 | The Paradox | SRFSUP::FRIEDMAN | Thu Dec 17 1987 16:34 | 17 | |
The prisoner reasons that he cannot be executed on Friday, the last
day, because if he survived past Thursday morning, he would know
for sure that he would be executed on Friday.
He further reasons that he cannot be executed on Thursday, because
if he survived past Wednesday morning, he would know for sure that
he would be executed on Thursday, since Friday has already been
ruled out.
He continues along this vein, ruling out Wednesday, Tuesday, and
Monday. He smugly concludes that the sentence cannot be carried
out.
On Wednesday morning he is roused from his jail cell and executed.
The sentence is thus carried out.
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| 805.3 | ex | SRFSUP::FRIEDMAN | Thu Dec 17 1987 16:36 | 5 | |
The resolution of the paradox lies in S�ren Kierkegaard's famous
quotation:
"Life can only be understood backwards but must be
lived forwards."
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| 805.4 | Martin Gardner... | CHOVAX::YOUNG | Back from the Shadows Again, | Fri Dec 18 1987 10:03 | 4 |
The paradox is very eloquently explained and discussed in Martin
Gardner's "The Unexpected Hanging & other paradoxes"
-- Barry
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