One usable measurement from six, never replicated, and the number is still in circulation.
Soul
What makes a living thing alive - which for Aristotle includes plants, and for the modern reader means almost the opposite.
- Theme
- Cosmos, the sacred and ultimate reality
- Tradition
- Cross-tradition
- Term
- ψυχή · psuchē
- Term fixed
- c. 330 BC
In plain terms
For Aristotle a plant has a soul. That sounds like a mistake and is not - it is what the word meant.
Psuchē is what makes a living thing alive: the organisation that makes this matter a functioning organism rather than a heap. Plants have the nutritive kind, animals add perception and movement, humans add reason. On that account the soul is not a passenger inside the body. It is the body's form, and asking whether it survives the body is like asking whether the shape of a statue survives the melting.
The familiar sense - an immaterial self that inhabits a body and outlives it - is Plato's, taken up by Christianity. Two incompatible pictures, one word, and most disagreements about the soul are people using different ones.
As a philosopher would put it
Aristotle defines psuchē as the first actuality of a natural body having life potentially - the form of an organised body, not a substance in its own right. The consequence is that the soul cannot straightforwardly survive, and his remarks about the intellect are among the most disputed in his corpus, generating the medieval controversy over whether the active intellect is individual or shared.
Plato's picture is the rival: the soul is simple, pre-exists the body, is imprisoned in it, and survives - which the Phaedo argues at length and the tradition adopted.
Aquinas attempts a synthesis, making the soul the form of the body and subsistent, which allows survival while denying that a separated soul is the person - a position that requires bodily resurrection to complete.
Ibn Sīnā's floating man argues for the soul's independence from the body by asking what a person created suspended in the air, with no sensation, would still be aware of. Buddhist anātman denies the whole category.
Where you meet it
In 1907 Duncan MacDougall, a physician in Haverhill, Massachusetts, weighed six dying patients on a specially built bed frame, expecting a loss at the moment of death.
His published account reports that one patient showed a sudden drop of about three quarters of an ounce - roughly twenty-one grams. Of the remaining five, two were discarded for technical failures, two showed changes he had to reinterpret, and one was excluded because the scales had not been calibrated.
One usable measurement, from a sample of six, never replicated, in an experiment with no control for evaporation, bowel and bladder release, or the mechanics of a beam balance under a shifting load.
The figure entered folklore anyway and has stayed there for over a century, supplying a film title and a persistent internet claim. What it demonstrates is not anything about the soul but the appetite for a physical test of a concept whose classical versions were designed to be untestable in exactly that way.
What is actually disputed
Whether there is anything for the word to name.
Physicalists hold that the functions once assigned to a soul - life, perception, thought - are performed by an organism, and that positing an additional item explains nothing and raises the interaction problem.
Dualists reply that the felt character of experience is not accounted for by any functional description, which keeps the question open under a different name.
The Aristotelian position is a third option that neither side represents well: the soul is real, is not a separate substance, and is not reducible to matter either, because form is not matter. Whether that position is coherent or a way of not choosing is argued in every generation.
And the traditions divide on what would even be at stake. If Buddhism is right that no persisting self is found, then the whole question of the soul's survival concerns something that was never there to survive.
Commonly confused with
- Mind c. 450 BC Mind is a functional and epistemic category. Soul carries claims about life, value and survival that mind does not.
- Self 1694 The self is the question of whether there is a subject. Soul is a proposed answer with a particular metaphysics attached.
- Consciousness 1641 Aristotle's soul includes the nutritive functions of plants, which involve no consciousness at all.
Defined against
- Anātman The Buddhist denial is aimed at exactly what most soul doctrines assert, and neither tradition regards the disagreement as verbal
Philosophers
- Aristotle The soul as the form of a living body
- Plato The soul as simple, pre-existent and surviving
- Thomas Aquinas The synthesis, form and subsistent at once
- Avicenna The floating man and the soul's independence
- René Descartes The thinking substance, distinct from extension
- Buddha The denial that any such thing is found
Works
- Metaphysics The soul as form and first actuality
- Phaedo The arguments for immortality
- Summa Theologiae The scholastic synthesis
- The Book of Healing The floating man
- Meditations on First Philosophy The thinking substance
- Abhidharmakosa The analysis into aggregates, with no soul
Schools
- Peripatetic school (Aristotelianism) Where the soul is form
- Old Academy Where it is separable and immortal
- Thomism Where the two are combined
- Avicennism Where its independence is argued
- Cartesianism Where it becomes a thinking substance
- Early Theravada Buddhism Where the category is denied
Related concepts
Mind c. 450 BC · Immortality c. 380 BC · Self 1694 · Ātman c. 700 BC · Anātman c. 450 BC
Aristotle's psuchē is the form of a living body and belongs to plants and animals as much as to humans; the modern sense of an immaterial personal survivor is Platonic and Christian rather than Aristotelian.