The weight of the soul, or the 21-gram experiment

For centuries, Western culture has housed, among its repertoire of ideas and beliefs about the afterlife, the assumption that the essence of human beings is found in an immaterial substance that we usually call soul.

The soul is a concept as mysterious as imprecise and confusing, and that is why it is so disdained by science, in charge of describing nature from small prudent observations and assumptions, as used by religions, which in a very ambitious way appeal to the great mysteries that from an immaterial world seem to guide order of the cosmos.

Soul, a disputed concept

However, at the beginning of the 20th century, a doctor named Duncan MacDougall set out to break with this logic by search for evidence of the existence of the disembodied essence of human beings in a simple experiment based on the use of scales. The idea from which this researcher started was that if the soul left some kind of trace in the body that had housed it, it must be found at the time of death, which is when it 

leaves the body to pass to another plane of reality. For this reason, he maintained that the death of people not only supposes the disappearance of voluntary movements and the cessation of mental activity, but also had repercussions on the weight of the body.

A body that lacked the essence that he defined as something human, with intentions and will: the soul.

MacDougall wanted to weigh the soul, to compress millennia of affirmations about the afterlife in the discreet movement of a needle. This was what led him to argue that the physical embodiment of the existence of the soul could be found in, more or less, 21 grams of difference.

How was the 21 gram experiment done?

Duncan MacDougall wanted to collect evidence from him about the existence of the human soul using a complex system of scales incorporated into a kind of bed as an instrument. In this way, he convinced six people who were dying to spend their last hours in that type of structure, which he allowed her to record the weight of their bodies from a few hours before their deaths until just after.

From these results, MacDougall concluded that the soul weighs approximately 21 grams, which is the variation that he was able to observe through his research. This statement had a considerable impact on the press, which through the New York Times echoed the news even before a version of it appeared in academic journals. Thus, the idea that the soul could weigh about 21 grams has taken strong root in popular culture, which explains why references to this experiment appear in musical pieces, novels and movies, being the most notorious 21 grams by director Alejandro González Iñárritu.

the controversy

While it is true that the New York Times article on Duncan MacDougall and the weight of the soul had a lot of impact, it is also true that it was not unanimously received positively. The scientific community of that time was already highly suspicious of experimental forays into the realm. of the supernatural, and the 21-gram experiment was based on ideas that directly undermined the parsimony principle, used in science to indicate that the explanations for an objective fact must be as simple as possible. That is why the results obtained by this doctor divided the public into two polarized positions.

To reinforce his results, MacDougall performed a variant of the experiment using dogs, to conclude that there was no noticeable change in the weight of these animals before and after death, which would indicate that, as certain religious beliefs hold, non-human animals lack soul. As is to be expected, this just added fuel to the fire.

Does this sound reasonable?

MacDougall hoped to take advantage of (at the time) recent technological advances and the refinement of the scientific method to access to a type of knowledge that for millennia had been unattainable for humanity, but that is related to a plane of the existence associated with the eternal, the essence of human beings and, in general, entities that inhabit what is beyond the realm of what physical. Taking that into account, no wonder the conclusions he reached were so incendiary.

An experiment mediated by irrational beliefs

On the one hand, the experiment of the 21 grams talks about dogmas, questions of faith, the essence of what is human and certain elements related to the realm of the sacred. On the other, it seemed to be an instrument to blur the limits of what can and should be studied scientifically. The mere fact that MacDougall wanted to investigate the soul through the scientific method was a provocation, and many researchers were quick to point out a large number of methodological flaws in the procedures he followed Duncan.

However, beyond the consideration of the many errors that were made during the experiments, other philosophical questions remained. fundamentals: Is not learning about the immaterial world and mystery the most ambitious type of knowledge that the science? Doesn't the fact that the nature of the human soul has been discussed for millennia make this matter a particularly interesting topic for the scientific community?

The answer is... No

With hindsight, and from what is known about the experiments performed by Duncan MacDougall, it is clear that the large number of methodological flaws make it we cannot even take seriously the statement that bodies lose about 21 grams at death. However, what makes these investigations only have value as a historical curiosity are not these errors, but the objectives towards which they were aimed.

The soul does not weigh 21 grams

To give an explanation about a process linked to the world of the physical, one cannot appeal to the world of the immaterial, but rather seek the answers in the nature that surrounds us.

This is what, for example, the physician Augustus P. clarke, what linked weight loss to increased sweating right after death, due to the general heating of the body as the organs in charge of ventilation, that is, the lungs, do not work. In turn, Clarke pointed to the fact that dogs do not have sweat glands spread throughout their bodies, which would explain why there was no change in their weight after death.

Of course, the very definition of the concept of soul is very plural, conflictive and contains many contradictions (how can something incorporeal inhabit inside the body of living beings?). However, what makes its study not a task for science is the fact that when we talk about the soul we are talking about something that has no physical entity and, therefore, it cannot be measured nor can it be modified by what happens to the body.

If we assume that an extraordinary claim needs to be supported by equally extraordinary evidence, we will see that there is a leap of evident faith that goes from the verification of a change in weight to the idea that this is due to the fact that the soul has abandoned the body. In fact, in the case of concluding that the 21 grams serve as evidence that there is a supernatural entity that inhabits people, rather than offering an explanation to the Observed fact, we will be doing just the opposite: creating a practically infinite number of questions that cannot be answered from more verifications. empirical.

After death, what do we have left?

The 21-gram difference recorded by Duncan MacDougall was intended to be much more than justification of what led to carry out the experiment (detect a change in weight before and after death) but that It was raised as a window to the world beyond. The hypothesis to be tested could only be sustained on a religious belief system accumulated for centuries, and lost all meaning when separated from it to be placed under the magnifying glass of method scientist.

However, while it is true that the 21-gram experiment has no scientific value, it has shown extraordinary robustness when it comes to surviving in the collective imagination of society. This is probably because MacDougall's beliefs about the soul a hundred years ago are still very much alive today.

No.Our cultural background makes us pay more attention to an apparently scientific article that confirms our beliefs than a 200-page book written decades ago that talks about why science only deals with talking about processes based on material. The scientific mindset may have many tools to perpetuate itself, but it's still not as seductive as certain ideas about the afterlife.