Death, a question...

in my short career-span as a doctor, i have declared many patients dead... and probably this is the first time that i have pondered over it. the ancient Greeks suggested waiting for 3 days and the Romans 9 days, to ensure the person was indeed dead!!! Indian literature mentions cutting a finger or observing if ghee placed on the forehead melts... someone rightly said, "so uncertain is men's judgement that they cannot determine even death itself"...