What is the 21 grams postulate from 1907?

08 October 2006



I'm researching the 21 grams postulate from 1907. What can you tell me about it or refer me to in order to prove or disprove this urban myth?


I actually had another email about this. It stems from 1907 and it comes from an American doctor, Duncan MacDougall, who tried to work out how much your soul weighs. People have thought for thousands of years that there's some life force or soul that makes us human, and when we die it leaves the body. As it exists, it must be made of something, and if it's made of something then it must weigh something. The easy way to find out how much it weighs is to weigh someone at the moment they die. What he did was to recruit six terminally ill patients, and selected ones that wouldn't thrash around too much at the time of death because that would obviously skew his results a little bit. He had this special bed balance made up and installed into his hospital. One patient lost, he says, three fourths of an ounce, which is twenty one grams. He then published this in American Medicine and it got picked up as 'the soul weighs 21 grams' and there was a massive splash about it. But actually it's wrong, because if you go and examine the rest of his results more carefully, you'll find that there's a little bit of a bias in how he's reported it. One of the people lost 21 grams; two of the people were discounted from the study for 'technical reasons'; a third person lost a load of weight and then put it back on again; and the final two lost a load of weight and then lost a load more, suggesting that they died more than once - I'm not sure! This is where this stems from, and it just shows that if you do careless research it can be quickly picked up and turned into a massive urban myth.


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