Simple Enough
Before his students arrived for a graduate course in logic, Raymond Smullyan wrote on the blackboard:
PLEASE DO NOT ERASE — BECAUSE IF YOU DO, THOSE WHO COME LATER WON’T KNOW THAT THEY SHOULDN’T ERASE.
An idler's miscellany of compendious amusements
Before his students arrived for a graduate course in logic, Raymond Smullyan wrote on the blackboard:
PLEASE DO NOT ERASE — BECAUSE IF YOU DO, THOSE WHO COME LATER WON’T KNOW THAT THEY SHOULDN’T ERASE.
