Minor Biological Works (Parva Naturalia)

Overview

About a hundred pages, a collection of seven short treatises, plus a few additional minor pieces in some editions, generally grouped together under the Latin title Parva Naturalia, meaning roughly small works on nature, written by Aristotle around 350 BCE as a direct continuation of On the Soul. Where that longer treatise addresses the soul in general, defining it as the form or organizing principle of a living body and working out the general capacities, nutritive, perceptive, locomotive, rational, that distinguish different kinds of living things, these shorter works turn to specific activities that a living creature performs through the combined operation of soul and body together, neither purely mental nor purely physical in Aristotle’s own framework, which does not recognize that later distinction in anything like modern terms.

The individual treatises, in the order they are usually printed, are On Sense and Sensibilia, On Memory and Recollection, On Sleep and Waking, On Dreams, On Divination in Sleep, On Length and Shortness of Life, and On Youth and Old Age, On Life and Death, and On Respiration, the last three sometimes printed as a single continuous work given how closely their subject matter and argument interlock. Together they constitute Aristotle’s most concrete and physiologically grounded account of mental and vital activity, complementing the more abstract, definitional treatment of soul found in On the Soul itself.

What happens

On Sense and Sensibilia. Aristotle examines the objects proper to each of the five senses, color for sight, sound for hearing, and so on, and the physical media, light, air, through which sensation occurs. The treatise’s most philosophically significant contribution comes in its later chapters, where Aristotle argues for what later commentators called a common sense, a further faculty distinct from any of the five particular senses, by which we perceive that we are perceiving at all, compare and distinguish qualities reported by different senses, sweetness against whiteness, for instance, and unify the separate deliverances of sight, touch, hearing, taste and smell into a single, coherent experience of one object in the world rather than five disconnected reports. This account of sensory integration anticipates, in its own terms, questions that remain genuinely live in modern philosophy of mind and cognitive science under headings like the binding problem, how a brain that processes different sensory modalities through largely separate channels nonetheless produces one unified conscious experience.

On Memory and Recollection. Aristotle draws a careful distinction between memory in the simple sense, the passive retention of an impression from a past experience, available even to some non-human animals on his account, and recollection, a more active and specifically human capacity involving a kind of deliberate search for a particular memory, proceeding by following chains of association, one image or idea calling to mind another related to it by contiguity, similarity or contrast. This associative account of how recollection actually works, moving along a trail of related images until the sought memory is finally retrieved, proved enormously influential, providing much of the conceptual vocabulary later taken up by empiricist philosophers of mind and by the early history of associationist psychology.

On Sleep and Waking. Aristotle offers a physiological explanation of sleep, tying it directly to the process of digestion: vapors and heat generated by digesting food rise toward the heart, which functions in his physiology as the central organ of sensation, and this rising heat temporarily incapacitates the sense faculties, producing the characteristic loss of waking sensory awareness that constitutes sleep. He is careful to distinguish sleep, a temporary and necessary incapacitation serving the body’s ongoing physical maintenance, from more final and pathological losses of sensory function, and from death itself, addressed more fully in the later treatises in the collection.

On Dreams. Aristotle asks what dreams actually are and how they arise, and his answer is notably deflationary relative to much ancient and popular opinion about dreams as sources of genuine insight or supernatural communication. He argues that dreams arise from residual sensory movements, faint impressions left over from waking perception, that continue to move and combine within the sense faculties during sleep, when the mind’s normal capacity to judge and correct perception against external reality is itself suspended, producing the characteristic confusion and apparent strangeness of dream experience without any need to posit external or supernatural causes.

On Divination in Sleep. A short companion piece directly addressing the popular belief that dreams can predict the future. Aristotle is skeptical but not entirely dismissive: he denies that dreams are literally sent by the gods as prophecy, but allows that some apparent predictive dreams may have a natural, if limited, explanation, either because a sleeper, freed from the distraction of waking sensory input, becomes more attuned to subtle bodily signs of an oncoming illness or change that will indeed manifest later, or through simple coincidence operating across the very large number of dreams people have, meaning that some dreams will inevitably seem, after the fact, to have anticipated events they had no genuine causal connection to at all.

On Length and Shortness of Life, and On Youth and Old Age, On Life and Death, and On Respiration. These closely related final treatises develop a unified physiological theory of aging, life and death organized around the concept of an innate vital heat, centered in the heart, that every living creature possesses from birth and that is gradually and irreversibly consumed over the course of a lifetime. Youth is the period during which this vital heat is still relatively abundant and even increasing through growth; old age is the period of its inexorable decline; and death occurs, on this account, when the vital heat is finally extinguished entirely, whether gradually through natural aging or suddenly through violence, disease or other external causes that exhaust or extinguish it prematurely. Respiration, breathing, is explained as serving the essential function of cooling this vital heat, preventing it from being consumed too quickly, which is why, on Aristotle’s account, creatures that breathe are able to sustain their internal heat, and therefore their life, considerably longer than they otherwise could.

How to read it

Read On Sense and Sensibilia and On Memory and Recollection first; these two treatises contain the collection’s most philosophically durable contributions, the theory of a unifying common sense and the associative account of recollection, and both remain genuinely engaged with by later philosophy of mind in ways the more purely physiological treatises do not.

Read On Sleep and Waking, On Dreams and On Divination in Sleep together as a connected sequence; Aristotle is working through one continuous problem across these three short pieces, what sleep is, what dreams are, and whether dreams mean anything, and the argument builds cumulatively across all three.

Notice how consistently Aristotle explains mental and vital phenomena through physiological mechanism, vapors rising to the heart, an innate heat being consumed, rather than through anything resembling a purely immaterial or disembodied account of mind. This thoroughgoing physiological orientation is characteristic of Aristotelian psychology generally and distinguishes it sharply from later, more dualist traditions in the philosophy of mind.

Read On Youth and Old Age, On Life and Death, and On Respiration as a single continuous treatise rather than as separate pieces, since their argument about vital heat runs continuously across all three and the traditional division into separate titles somewhat obscures how tightly integrated the underlying theory actually is.

Read this collection immediately after On the Soul if you have read that longer treatise, since these shorter works consistently presuppose and build on the general framework, form and matter, the hierarchy of psychic capacities, established there, applying it to specific, concrete activities rather than developing new foundational theory of their own.

Questions it raises

• Is Aristotle’s common sense a genuine solution to the problem of unified perceptual experience across different sensory modalities, or does it merely relocate the problem to a further, unexplained faculty?
• Does the distinction between passive memory and active, associative recollection still hold up as an account of how remembering actually works, given what is now known about memory from cognitive science?
• Aristotle’s skepticism about prophetic dreams allows for some natural explanations of apparently predictive dreaming. Are these natural explanations more or less satisfying than either full skepticism or full credulity about dream prophecy?
• What does explaining sleep, aging and death through a single physiological mechanism, vital heat, gain in explanatory unity, and what does it lose in accuracy once compared with modern physiology?
• How does Aristotle’s thoroughly embodied, physiological account of mental activity compare with later philosophical traditions that treat mind and body as fundamentally distinct kinds of thing?
• Given how much of ancient physiology in these treatises has been superseded, what, if anything, of lasting value remains in Aristotle’s specific explanatory mechanisms, as opposed to his more general philosophical framework for thinking about soul and body together?