Common to Body and Soul: Avicenna on Sleep as an Affection of the Animal Body

In his "De somno et vigilia", Aristotle provides the first philosophical account of sleep (and wakefulness). He considers these as two contrary states: overall, the former is a condition of privation of the features that qualify the latter. Aristotle’s account of sleep as we know it seems not to have influenced subsequent reflection on the topic in the Islamicate world. Philosophers had access to an adaptation of this text in which fragments of the original Greek text were interspersed among material belonging to other (philosophical and medical) traditions. This adaptation develops some ideas, already present in the Aristotelian text, about sleep as the context for a specific form of perception and motion. The first philosopher in the Islamicate world to engage with this text and provide a similar exposition on sleep was Avicenna (Ibn Sīnā, d. 1037). Being a philosopher and a physician, in his writing on psychology, Avicenna combines the philosophical account of the specific form of perception and motion occurring during sleep with an exposition of the physiological aspects connected with this state.