P.M.S. Hacker. Human Nature: The Categorial Framework
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«The Aristotelian tradition, as one might expect of its originator, is inspired primarily by biological reflection. The Aristotelian concept of the psychē (a term commonly translated, somewhat misleadingly, as ‘soul’) is a biological concept, not a psychological, let alone a theological or ethical, one. The psychē is conceived to be the source of the distinctive activities of a living thing – the ‘principle’ of life that makes it the kind of being that it is. The soul, as Aristotle conceived it, is the set of potentialities the exercise of which is characteristic of the organism. Consequently, it is not only human beings that have a psychē, but all living creatures, including plants. What is distinctive about the human soul is that it incorporates not only the vegetative powers of growth, nutrition and reproduction, and the sensitive powers of perception, desire and motion, but also the uniquely human rational faculties of will and intellect. The soul is not an entity attached to the body, but is characterized, in Aristotelian jargon, as the ‘form’ of the living body. The soul stands to the body of a human being roughly as the power of sight stands to the eye. The powers of a thing cannot survive the death of the thing itself. However, Aristotle equivocated, sometimes arguing that the rational soul, in particular the capacity to reflect on necessary truths (later denominated ‘the agent intellect’), is itself immortal. This, not obviously coherent idea, was to be the handle that Aquinas seized in order to accommodate Aristotelian philosophy to Christian doctrine.»