Three or One or None? A Short History of the "Soul"

Aristotle held that living things possess a vegetative or nutritive soul, animals add a sensitive soul, and humans add a rational soul. Medieval pluralists like Robert Kilwardby treated vegetative, sensitive, and rational souls as distinct entities stacked in one body to explain Christ’s holy body after the human soul departed. Unitists such as Thomas Aquinas argued multiple souls would form only a parts-bundle, not a unified substance, and his single-soul view was briefly banned in Paris and Oxford. Descartes then claimed only humans and higher beings have both an immaterial soul and a physical body, while animals are soulless automata whose behavior follows from organ arrangement like a clock.

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