What is the Soul? From Egypt and Plato to Neuroscience
We all know the word 'soul', but every age has understood it differently. The history of this concept is the history of the question of who we actually are.
Ezostylia Editorial Team · facts checked in sources · updated 31.10.2026
Egypt: Several Souls at Once
The Egyptians believed that a person possessed several spiritual components. Ka was the life force, which required food in the tomb; ba was depicted as a bird with a human head that could fly out of the tomb; and akh was the transformed, luminous spirit of the deceased.
Greece: Psyche
For Homer, psyche is the breath that leaves the body at death and passes into Hades as a pale shadow. Plato made the soul something immortal and divine, imprisoned within the body. Aristotle saw it differently: the soul is the form of the living body, just as sight is the 'soul' of the eye.
World Religions
- Christianity: an immortal soul created by God, united with the body, which will be resurrected.
- Islam: ruh, the breath of God, which after death awaits the Day of Judgement.
- Hinduism: atman, the eternal self, which in the deepest sense is one with the absolute (brahman).
- Buddhism: no enduring soul; what we call the 'self' is a changing stream.
Science: The Problem of Consciousness
Neuroscience demonstrates how closely experiences, memory, and personality depend on the workings of the brain. Yet it remains unknown why we have any experiences at all. The philosopher David Chalmers called this the 'hard problem of consciousness', and that question remains open.
How Much Does the Soul Weigh?
In 1907, the American physician Duncan MacDougall claimed that the body loses 21 grams at the moment of death. He studied only a handful of patients, and his measurements were inconsistent, so science regards this result as unreliable. The figure of 21 grams has nonetheless survived in culture, most notably as the title of a film.
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You will find all 30 topics in the section Mysteries of life and death.
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Sources
Frequently asked questions
How much does the soul weigh?
It cannot be measured. The famous '21 grams' comes from an experiment conducted by Duncan MacDougall in 1907, which was carried out on only a few individuals and has never been confirmed.