Parva Naturalia (Short Treatises on Nature)

Summary

The Parva Naturalia, 'little works on nature', is the medieval Latin name for a group of short treatises in which Aristotle carries the theory of the soul from On the Soul (De Anima) into the body. His opening sentence announces the plan: having considered the soul by itself, he will now examine the activities that belong to soul and body together, such as sensation, memory, passion, appetite, sleep and waking, youth and age, breathing, life and death. The library's text, from the Oxford translation, contains the treatises On Sense and the Sensible, On Memory and Reminiscence, On Sleep and Sleeplessness, On Dreams, On Prophesying by Dreams, On Longevity and Shortness of Life, and a combined treatise On Youth and Old Age, On Life and Death, On Breathing. On Sense examines the organs of the five senses and their objects, rejecting Plato's and Empedocles' theory that the eye sees by sending out fire, and arguing that hearing, because it carries speech, contributes most to learning. On Memory distinguishes memory, a lasting image of something perceived and marked as past, from recollection, an active search through a chain of associated movements, which Aristotle thinks only human beings perform. He compares memory to the impression of a seal and explains why the very young, the very old, and people too quick or too slow remember badly. On Sleep calls sleep a seizure of the primary sense faculty seated in the heart, brought on by vapours rising from digested food and cooled in the head, and argues that it exists for the preservation of the animal. On Dreams treats dreams as residual movements of earlier perceptions, noticed when waking sense falls silent, and explains how emotion and fever make faint likenesses seem real. On Prophesying by Dreams cautiously concludes that most apparently prophetic dreams are coincidences, though some may be signs of bodily conditions or causes of later actions, and that dreams are not sent by God, since animals also dream. The last treatises connect length of life, ageing and death with the natural heat of the heart and with the cooling provided by lungs or gills, and survey the breathing of many kinds of animals. For readers interested in medicine, the collection is one of the founding texts of the physiology of sleep, memory and ageing. Aristotle opens and closes it by noting that natural philosophers and philosophically minded physicians meet on the ground of health and disease, and the work shaped Galenic, Arabic and medieval university medicine. Its physiology, centred on the heart rather than the brain, is mistaken, yet its careful descriptions of memory, recollection, and the way emotion distorts perception remain worth testing against experience.

Top Lessons

• Memory as the seal, recollection as the hunt

  Aristotle distinguishes the passive persistence of an image from the active search by which we recover it, noting that slow people often have good memories while the quick are better at recollecting. His account of association, moving from one thing to what is like it, opposite to it or next to it, is the root of much later psychology. Students can test it against their own study habits.

• Why the frightened see what they fear

  In On Dreams, Part 2, Aristotle observes that the angry, the desirous and the frightened are easily deceived, and that the more intense the passion, the less resemblance is needed to produce an illusion. The feverish patient who sees animals in the wall pattern is his example. The lesson is moral as well as physiological: passion clouds judgment, and self-command helps us see truly.

• Weighing a prophetic dream without credulity or contempt

  On Prophesying by Dreams begins by saying the subject should be neither despised nor easily believed. Aristotle then sorts dreams into causes, signs and coincidences, and concludes that they are not sent by God, while still calling nature divinely ordered. Christian readers can admire his discipline while noting that Scripture records God speaking through dreams to Joseph, Daniel and others, a possibility Aristotle's reasoning does not consider.

• Old age as a flame burning low

  The treatise On Youth and Old Age, On Life and Death explains life as the preservation of the heart's natural heat and old age as its gradual exhaustion, so that death in old age comes gently, like a small flame going out. Though the physiology is mistaken, the image shaped centuries of medical thinking about ageing and invites reflection on how to regard the end of life.

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Medical Lens

Medical relevance was raised from none to high because the treatises themselves deal directly with sleep, dreams, memory, epilepsy, the melancholic temperament, fever delirium, ageing and death, and twice address the relation of natural philosophy to medicine. Aristotle's cardiocentric physiology (sensation seated in the heart, sleep caused by digestive vapours cooled in the brain) was rejected by Galen's brain-centred account, but his descriptions of association in recollection, of emotion-driven illusions, and of dreams as possible early signs of illness entered Galenic, Arabic and medieval medicine. His 'atrabilious' or melancholic persons belong to the humoral framework; any correlation with modern diagnoses is a reading, not a fact.

• On Sense and the Sensible, Part 1

  Programme of the collection: the physical philosopher should know the first principles of health and disease, and philosophical physicians build their medicine on natural science.

• On Memory and Reminiscence, Parts 1-2

  Memory as an impression like a seal; defective memory in the very young, the very old, and those too quick or slow; recollection that persists uncomfortably in persons of melancholic temperament.

• On Sleep and Sleeplessness, Parts 2-3

  Sleep as an incapacity of the primary sense organ in the heart, caused by vapour from digestion; sleepiness after meals, in infants, in fever and lethargy; sleep compared to epilepsy; the atrabilious not given to sleep.

• On Dreams, Parts 2-3

  After-images and persistence of sensation; illusions in anger, desire, fear and fever delirium; unhealthy, confused dreams in the atrabilious, the feverish and the drunk.

• On Prophesying by Dreams, Parts 1-2

  Physicians attend to dreams because slight bodily movements unnoticed by day may become perceptible in sleep; melancholic and excitable temperaments have vivid and apparently prophetic dreams.

• On Youth and Old Age, On Life and Death, On Breathing, Parts 23 and 27

  Death as extinction of the heart's natural heat; painless death in old age; diseases that harden the lung or cause fever accelerate breathing; closing remarks on the shared ground of physicians and natural scientists.