Dreamless Sleep, the Embodied Mind, and Consciousness

One of the major debates in classical Indian philosophy concerned whether consciousness is present or absent in dreamless sleep. The philosophical schools of Advaita Vedānta and Yoga maintained that consciousness is present in dreamless sleep, whereas the Nyāya school maintained that it is absent. Consideration of this debate, especially the reasoning used by Advaita Vedānta to rebut the Nyāya view, calls into question the standard neuroscientific way of operationally defining consciousness as “that which disappears in dreamless sleep and reappears when we wake up or dream.” The Indian debate also offers new resources for contemporary philosophy of mind. At the same time, findings from cognitive neuroscience have important implications for Indian debates about cognition during sleep, as well as for Indian and Western philosophical discussions of the self and its relationship to the body. Finally, considerations about sleep drawn from the Indian materials suggest that we need a more refined taxonomy of sleep states than that which sleep science currently employs, and that contemplative methods of mind training are relevant for advancing the neurophenomenology of sleep and consciousness.