Life Force and Gravity: Does The Soul Just Weigh 21 Grams?

Abstract image of the soul.

Twenty-one grams is an experiment by Dr. Duncan MacDougall based on the hypothesis that human souls have physical weight. (Image: Alexandra Barbu via Dreamstime)

Twenty-one grams is an experiment by Dr. Duncan MacDougall based on the hypothesis that human souls have physical weight. He tried to measure the mass change of six dying patients. One of the six patients lost three-quarters of an ounce or 21.3 grams. 

While MacDougall’s experiment was rejected within the scientific community, it popularized the concept that the weight of the human soul is 21 grams. In addition, the investigation inspired Dan Brown to create a novel entitled The Lost Symbol. And was also mentioned in Mary Roach’s book The Curious Lives of Human Cadavers and inspired the movie 21 Grams.   

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Dr. Duncan MacDougall, pictured in 1911. (Image: via Public Domain)

The 21-gram experiment 

Dr. Duncan MacDougall’s experiment was based on the idea of a “physical soul,” which loses weight as the soul leaves the body. He believed that the soul was material and had mass. For this reason, he thought a dying patient would have measurable weight loss at his death. 

He performed his experiment at The Cullis Consumptives Homes in Boston in 1907, where he was serving as a volunteer. He constructed a unique bed in his office using balanced platform beam scales. For his subjects, he experimented with six terminally ill patients nearing their end stage. 

MacDougall observed the patients before, during, and after their death during the experiment. He measured any weight changes. And discovered that the patients lost weight at the time of death. Then repeated, the same experiment was on fifteen dogs but found no weight loss. This led him to the conclusion that the human soul had measurable mass. 

He also attributed the weight loss to various factors, such as moisture evaporation from the skin. He concluded that urine and fecal eliminations could not have contributed to the weight change, air loss in the lungs, and breathing.

Dr. MacDougall’s experiment had a much more significant impact on the religious community, which vehemently denied his experiment’s results. 

The Cullis Consumptives Homes in Boston. (Image: via Public Domain)

Arguments against the findings

While the 21-gram experiment aroused interest, scientists did not consider it great science. One such scientist is Donald Everhart, at The American Musical and Dramatic Academy, who was an expert in sociology and the philosophy of science. According to Everhart, the sample size was too small to be reliable. 

Director of Institutional Research, Everhart, claims that scientific experiments have nothing to do with probability and statistics. The use of statistical inference was less common in the scientific community than the use of logical deduction and precise measurements, he claimed. Everhart said that Dr. MacDougall should have taken a more scientific approach. 

French sociologist Emile Durkheim published a seminal work on suicide in 1897. To back up his assertions, he used official death figures. Everhart said that MacDougall should have considered how his study would have earned greater epistemological weight if it had uncovered more than one case. 

In addition, the experimental setup, a bed resting on a scale, could have been better for gauging an immaterial concept like the soul. Two of the six participants MacDougall tested on had to be dropped from the study due to complications. And one lost weight immediately, two lost weight but gained it back over time, and one lost weight, gained it back, and then lost it again. 

The experiment’s goal, which Everhart questioned, was to promote the idea that the soul was physical rather than spiritual. It baffled him that MacDougall had pushed to get his flawed experiment and reasoning published. He said that MacDougall should have read the work of Auguste Comte, whose theory of positivism espoused that all phenomena could be best explained by physical science instead of metaphysical. 

MacDougall’s experiment was successful because 21 grams resonated with the people of that time and even today.

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