“Somnology” (or “hypnology”) is said to be “the scientific study of sleep.” It would be of some interest to see what Buddhist sources have to say about asleep. Buddhist reflections of discourse on the phenomenon of sleep may be called “Buddhist Somnology.” “Buddhist Somnology” may be defined as a “Buddhist philosophy of sleep.” Some points to ponder about: (a) Is sleep not considered a mental state or factor (cittasika/caitta: sems las byung ba). One of the 51 such mental factors. It is also one of the gzhan ’gyur bzhi. That is, it axiological value is not fixed and hence can be transformed into positive, negative, or neutral. (b) Sleep is conceived of as having two levels or layers, namely, so to speak, light sleep in which dreams can be dreamt, and deep sleep (gnyid ’thug po), which is one of the five states of mindless-ness (sems med pa’i gnas skabs lnga), and is comparable to a state of coma.
Here is some thoughts that I have made previously and hence there are some repetitions:
I just happened to reflect on what Buddhist sources say on the phenomenon of sleep. Do they at all say something on the topic and if so what? Here are some random thoughts that occur to me. So what I say here should not be taken as representing my fixed position.
§1. I should first study James Hill, “The Philosophy of Sleep: The Views of Descartes, Locke and Leibniz.” Richmond Journal of Philosophy 6, 2004, pp. 1–7. A copy can be found here: http://www.richmond-philosophy.net/rjp/back_issues/rjp6_hill.pdf.
§2. What is sleep? Abhidharmically speaking, “sleep” (gnyid) is considered a “mental associate/factor” (caitta/caittasika: sems las byung ba), that is, one of the (usually) fifty-one caittas “cognitive factors/states” associated with cittas (or vijñānas), the principal cognitive subjects/agents, consisting of the six or eight perceptual-conceptual apparatuses. “Sleep” as a caitta should actually be understood a certain state of citta. It is also counted as one of the so-called gzhan ’gyur bzhi (Sanskrit terms will be added later). That is, gnyid, together with ’gyod pa, rtog pa, and dpyod pa, are considered to be “transformable” into either wholesome, unwholesome, or neutral, depending on the wholesome, unwholesome, or neutral state in which the principle mind, that is, I guess manovijñāna, finds itself, when the process of sleep takes place. The implication of such a theory for Buddhists is that if one spends half of one’s life in sleep, then at least the time spent sleeping would become meaningful. There may be other Abhidharma positions on this.
§3. Tibetan Buddhist sources seem to classify sleep into what one might call “[light] sleep” (perhaps just gnyid) and “deep sleep” (gnyid ’thug po). The difference between the two is that one is capable of dreams in the former state and not in the latter state. That is, no mental or cognitive activity would take place in a state of deep sleep. In fact, deep sleep is considered one of the “five situations in which citta is absent” (sems med pa’i gnas skabs lnga). (Sources for this will have to be added later.) Deep sleep, thus, may be said to be somewhat similar to a state of coma (although nowadays people seem to talk about different types/levels of coma). Such a concept of state must have posed doctrinal and exegetical problems. For example, why is a living person in a state of deep sleep not dead? The Yogācāras can be said to have come up with a solution, namely, a subliminal vijñāna called the ālayavijñāna. So for them, what ceases during a state of deep sleep and other states of mind-less-ness is the manovijñāna and others but not ālayavijñāna; ālayavijñāna can continue until one becomes a buddha.
§4. The “four states” (gnas skabs bzhi)—namely, “state of being awake” (sad pa’i gnas skabs), “state of dream” (rmi lam gyi gnas skabs), “state of deep sleep” (gnyid stug po’i gnas skabs), and “state of sexual union or meditative poise” (snyoms ’jug gi gnas skabs)—seem to comprise all possible states of one’s existence. Although the last state is understood by some to be only “state of sexual union,” I think, it should include any ecstatic or orgasmic state in which all conceptual constructions or conceptualisations cease.
§5. What is known as the “six intermediate states” (bar do drug) popular in certain Tibetan Buddhist traditions seems to encompass the entire states of existence.
§6. The Buddhist ideas about “dreams,” though related with the idea of “sleep” should be treated separately. My concern here is not “dreams” but “sleep.”
§7. Buddhist sources negatively associate “sleep” or “slumber” with “ignorance” and “dreams” with “delusions” and “illusions.” The Summum bonum in Buddhism (particularly for the Mahāyāna) is the state of being “Awakened” (buddha: sangs rgyas). Sleep is associated with “eye-closing” and “ignorance” whereas state of being awakened with “eye-opening” and “insight.” Metaphorically speaking, therefore, all of us (who are not yet buddhas) are still sleeping and dreaming.
§8. The statues of the reclining Buddha is described often as the “Sleeping Buddha.” I do not see any online references to a living (Tibetan) Buddhist master who is referred to as a “Sleeping Buddha.” But I do recall some Chinese Buddhist friends who referred to sMin-gling-khri-chen Rin-po-che (1931–2008) as a “Sleeping Buddha.” But why? Of course because he is said to be practising rDzogs-chen teachings, so to speak, in a sleeping mode! We critics and skeptics would have all kinds of explanations but let us withhold them for the time being. Our question here is that if the rDzogs-chen tradition takes for granted that there is a practice that can be practiced while sleeping (or perhaps just lying down), how does it doctrinally legitimise such a practice?
§9. Two kinds of ideas seem to be relevant for such a practice. First, the rDzogs-chen tradition maintains that its teachings can be practiced both by “hard-working ones” (brtson ’grus can) and “lazy ones” (le lo can). (Sources should be added later.) The implication is that just because one is “lazily” reclining down or sleeping, it does not mean that one is not practicing. The legend of Śāntideva (Śāntadeva) would be easily used to illustrate this. Most of us have no way to verify such a claim. Only the practitioner himself or herself would know if he or she is indeed practicing or just whiling away her or her time in sleep. Second, gNubs-chen’s bSam gtan mig sgron (pp. 351–352) seems to provide yet another doctrinal justification. The expression employed there is the “Mode of Great Meaningful Sleep” (don chen nyal mo’i tshul), that is, a mode in which the “king of awareness” (rig pa’i rgyal po) “sleeps or reclines” (mnal) in (ngang) the sphere of true reality (chos kyi dbyings). This idea is explained in a purely rDzogs-chen context.