In the two years since I’ve been writing this blog, we’ve explored just about every aspect of our anatomy, from the beautiful intricacies of its form and function to the bizarre ways we modify and even mutilate our bodies. So as this writing endeavor draws to a close and I focus on other projects, I thought I'd end by discussing an aspect of the body that has eluded scientists and philosophers for centuries – the quest for the human soul.
Throughout history, the soul has been part of our search for understanding how the human body works. Ancient terms to describe the soul – from Latin’s anima to the Greek psyche – usually refer to the vital forces within the body, be they motion, movement, or breath. And since the presence of the soul was believed to separate the living from the dead, it seemed only logical that it should reside somewhere in the body. All we had to do was find it.
Some of the earliest references to the soul go back over five thousand years to the Egyptians, who believed the soul was composed of five parts, the most important of which resided within the heart. The heart was believed to be the animating life force, the source of our feelings, thoughts, and will. In fact, the weight of the heart at death determined the soul’s destiny. If the heart was considered too heavy, it would be consumed by a demon, subsequently ending one’s bid for the afterlife. This cardiocentric view of the soul persisted throughout much of history.
Fast forward a few thousand years to the Greek poet Homer, who claimed there were two types of souls. The first, which resided somewhere in the chest, controlled our emotions, everything from joy to reason to rage. The second type of soul was tied to a person’s individual identity and appeared only in dreams. It had no specific location within the body, but served as the animating life force. Homer believed it was this aspect of the soul that fled the body at the time of death.
The foundations of Western philosophy, forged by the likes of Socrates, Aristotle, and Plato, also contemplated the riddles of the soul. Plato considered the soul to be of celestial origin, the immortal essence of a person that was divided into three parts. The rational aspect, which controlled reason, was of primary importance and thus located within the brain. The spirited aspect, responsible for courage, resided in the chest, and the appetitive portion, which governed love (of food, drink, and “loving delights”) was located in the abdomen. The goal of life was to achieve a balance within the soul, especially regarding spirits and appetites; a human struggle that continues to this day.
Plato’s student, Aristotle, stoked his own ideas about the soul. He agreed the soul formed the essence of an individual but, unlike Plato, Aristotle believed the soul could not be separated from the body. So much for its immortality… He too divided the soul into three parts but, in his view, the soul controlled bodily functions and was therefore defined as such: the vegetative function (nourishment and reproduction); the sensitive function (sensation and movement); and the intellectual function (cognition and deliberation). Aristotle also believed that all animals possessed a soul, although the intellectual functions were confined to humans. And like the Egyptians of long ago, Aristotle believed the heart served as keeper.
Early Christians took a broader view. The soul not only gave form to the body, but could be found in every aspect of our anatomy. It was believed the soul entered the body only after the fetus was fully formed. “Delayed ensoulment” coincided with the “quickening,” thus once the mother felt the baby move, the soul was considered to have arrived.
Around the seventh century AD, as the Dark Ages blanketed humanity, the belief in delayed ensoulment persisted. The Roman Catholic Church decreed abortion acceptable as long as it was carried out before the soul arrived, and this was upheld well into the 19th century.
With the blossoming of the Renaissance in the 1300s, Leonardo da Vinci incorporated the search for the soul in his anatomical studies, declaring the middle ventricle of the brain as the most logical spot. René Descartes took up the banner a few hundred years later, agreeing with Leo on the general location of the brain, but claiming the pineal gland was a more likely location.
As scientists learned more about the inner workings of the brain, belief in a craniocentric soul persisted, well into the 20th century. It seemed only natural that the seat of consciousness should also house the soul. But as science advanced and our understanding of the human body crystalized, the soul as animating life force slowly fell away. The mystical realms of life could now be understood in terms of biochemistry, neurology, and genetics, and issues of the soul were gradually relinquished to the theologians.
If you ask me if we possess a soul, I'd have to say I don’t know. The scientist in me embraces the tangible explanations for what constitutes a living body and I’m far more comfortable discussing cellular respiration than arguing the validity of delayed ensoulment.
But that in no way diminishes my fascination with life or the wonder I feel when I contemplate the intricacies of our anatomy. Regardless of our beliefs, we can all agree the human body is a truly astounding machine, one that not only sustains us but enables us to experience our world.
As for the ghost in the machine... I’ll leave that to the theologians.
Thank you so much for reading.