Aprinceto.3003
net.math
utzoo!decvax!ucbvax!ihnss!eagle!mhtsa!allegra!princeto!stat
Tue Mar 16 15:42:55 1982
Paradox
I have spent many hours discussing this paradox and have heard dozens
of attempts at resolving it and have never quite been satisfied.

Mr. Smith tells his class that he will give them a surprise test sometime
in April. He explains that by 'surprise' he means that they will not know
when they arrive in class on the day of the test whether they will be
writing the test that day. Alec Smart reasons that the test will not be
on the 30th, for it would then not be a surprise. 'Thus', he continues, 'on
the 29th, since I know it won't be on the 30th, he has to give it that day
if he hasn't already, so it can't be on the 29th.' Arguing inductively he
comes to the conclusion that the test cannot be given as a surprise on any
day in April, he doesn't study, and is quite suprised when Mr. Smith gives
a surprise test on the 17th of April. Why was Alec surprised?

Please respond to me at ...ihnss!mhtsa!allegra!princeton!stat.