In recent decades certain historians have intimated that Byzantine society - and monastics in particular - suffered from a lack of sleep (whether described in negative terms as sleep deprivation or sleep abstinence). Sleep-abstinence surely permeated Byzantine society: it is encountered in every age, sex and class, together with its institutions, beliefs, practices, rituals, morals and mythologies. However, sleep is a biological phenomenon as well. One cannot possibly appreciate the Byzantines' stance towards it, nor assess the veracity, aims and effectiveness of their ideas and...