Medicine and philosophy - Classical Homeopathy Online

Aristotle on sleep and dreams 177the other hand, does not know fatigue and the harder we exercise ourintellectual faculty, the better it functions. 22The way in which Aristotle arrives at these views is largely theoretical andby a priori reasoning. Sleep, he argues in chapter 1 of On Sleep and Waking,is the opposite of waking; and since waking consists in the exercise of thesensitive faculty, sleep must be the inactivity of this faculty. Sleep affects allanimals, because sensation is characteristic of animals. Plants do not sleep,because they have no perception. In fact, sleep is nothing but a state of whatAristotle elsewhere calls ‘first entelechy’, 23 a state of having a faculty withoutusing it, which may be beneficial in order to provide rest to the bodily partsinvolved in its exercise. Furthermore, Aristotle is characteristically keen tospecify that sleep is a particular kind of incapacitation of the sense facultyas distinct from other kinds of incapacitation, such as faint and epilepticseizure (456 b 9–16). He also applies his explanatory model of the four causes(which he reminds us of in 455 b 14–16) to the phenomenon of sleep, listingits formal, final, material and efficient causes, and leading up to two complementarydefinitions stating the material and the formal cause of sleep:the upward movement of the solid part of nutriment caused by innate heat, and itssubsequent condensation and return to the primary sense organ. And the definitionof sleep is that it is a seizure of the primary sense organ which prevents it frombeing activated, and which is necessary for the preservation of the living being;for a living being cannot continue to exist without the presence of those thingsthat contribute to its perfection; and rest (anapausis) secures preservation (sōtēria).(458 a 25–32)By contrast, there is little consideration, let alone evidence of systematicgathering and interpreting, of empirical evidence to back up the theoryarrived at. It is true that, in the course of his argument, Aristotle occasionallyrefers to empirical observations, or at least he makes a number of empiricalclaims, which can be listed as follows:1. Most animals have their eyes closed when they sleep (454 b 15ff.).2. Nutrition and growth are more active in sleep than in the waking state (455 a1–2).3. All animals have a sense of touch (455 a 6).4. In fainting fits, people lose sensation (455 b 6).5. Those who have the veins in the neck compressed become unconscious(455 b 7).6. Breathing and cooling take place in the heart (456 a 5).7. Insects that do not respire are seen to expand and contract (456 a 12).22 De an. 429 a 30–b 6. 23 De an. 412 a 25–6.